SERV1830 January 2007
GLOBAL GLO BAL SER SERVIC VICE E LE LEARN ARNING ING TECHNICAL PRESENT PRESENTA ATION
773F (E 773F (EED ED), ), 77 775F 5F (D (DLS LS)) OFF-HIGHWA OFF-HIGHW AY TRUCKS INTRODUCTION
Service Training Meeting Guide (STMG)
773F (EED) (EED),, 775F 775F (DLS) OFFOFF-HIGH HIGHW WAY TRUCKS - INTRODUCTION MEETING MEET ING GUIDE 830
VISUALS VISUA LS AND SCRIP SCRIPT T AUDIENCE
Level II - Service personnel who understand the principles of machine system operation, diagnostic equipment, and procedures for testing and adjusting.
CONTENT This presentation provides basic maintenance information and describes the systems operation of the monitoring system, engine, power train, steering, hoist and brakes for the 773F/775F Off-highway Trucks. Trucks. The Automatic Retarder Control (ARC) (ARC) and the Traction Control System (TCS) are also discussed. OBJECTIVES
After learning the information in this meeting guide, the serviceman will be able to: 1. locate and identify the the major components in the engine, power train, steering, and brakes; 2. explain the operation of the major components in in the systems; and 3. trace the flow of oil through through the systems. REFERENCES
773F/775F Operation and Maintenance Manual 773F/775F Parts Manual
SEBU7794 SEBP4306
PREREQUISITES
"Fundamentals of Engines Self Study Course" "Fundamentals of Mobile Hydraulics Self Study Course" "Fundamentals of Power Trains Self Study Course" "Fundamentals of Electrical Systems Self Study Course" STMG546 "Graphic Fluid Power Symbols"
Estimated Time: 24 Hours Visuals: 213 Handouts: 24 Form: SERV1830 Date: 1/07 © 2007 Caterpilla Caterpillarr Inc.
TEMV3001 TEMV3002 TEMV3003 TEMV3004 SESV1546
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SUPPLEMENTAL SUPPLEMENT AL MA MATERIAL TERIAL Reference Manuals
Fluid Power Graphic Symbols User's Guide Cold Weather Recommendations for Caterpillar Machines Caterpillar Machine Fluids Recommendations
SENR3981 SEBU5898 SEBU6250
Salesgrams and Product Bulletins
Training Bulletin "Caterpillar Transmission/Drive Train Oil" Product Bulletin "Reporting Particle Count By ISO Code" Salesgram "Caterpillar Extended Life Coolant" Product Data Sheet "Caterpillar Extended Life Coolant"
TEJB1002 PEJT5025 TEKQ0072 PEHP4036
Technical Instruction Modules on Legacy DVDs SERV1000-01 (These materials CANNOT be ordered separately.)
Automatic Retarder Control System Automatic Electronic Traction Aid 769C - 793B Off-highway Trucks--Suspension System Truck Payload Measurement System
SEGV2593 SEGV2585 SEGV2599 SEGV2579
Service Training Meeting Guides
STMG 713 "769D/771D/773D/775D Off-highway Trucks"
SERV1713
Video Tapes
Suspension Cylinder Charging TPMS Management/Technical Information TPMS Operating Tips Introduction to the Automatic Electronic Traction Aid Mining Trucks--Cleanliness and Component Life Oil Sampling--The Right Way
TEVN2155 AEVN2211 AEVN2212 SEVN9187 SEVN4142 PEVN4638
Booklets
Know Your Cooling System Diesel Fuels and Your Engine Oil and Your Engine Understanding The S•O•S Report
SEBD0518 SEBD0717 SEBD0640 TEJB1015
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SUPPLEMENT SUPPLE MENTAL AL MA MATERIA TERIAL L (Conti (Continued) nued) Special Instructions
Accessing Flash Software for Machines Cate Ca terp rpil illa larr Elec Electr tron onic ic Con Contr trol olss Serv Servic icee Code Code Inf Infor orma mati tion on Des Descr crip ipti tion on Lis Listt Using the 7X1700 Communication Adapter Group Using the 261-3363 Wireless Communications Adapter Use of CE Connector Tools Servicing DT Connectors Parts Listing Of The Deutsch Connectors And Components Use of 6V3000 Sure-Seal Repair Kit Use of 8T5200 Signal Generator/Counter Group Suspension Cylinder Servicing 773F/775F Assembly Procedure
REHS0494 REHS RE HS01 0126 26 SEHS9264 NEHS0926 SEHS9065 SEHS9615 REHS0148 SMHS7531 SEHS8579 SEHS9411 REHS2704
Brochures
Caterpillar Electronic Technician Caterpillar DataView Diesel Engine Oil (CH4) Product Data Sheet How to Take a Good Oil Sample S•O•S Coolant Analysis Air Filter Service Indicator Cat Oil Cooled, Multiple Disc Brakes Caterpillar Automatic Retarder Control Caterpillar Truck Frames Mining Truck Bo Bodies: Selecting The Ri Right Bod ody y Sy System For For Your Job Caterpillar Truck Truck Production Management System: Answering your questions about TPMS
NEHP5614 NEHP5622 PEHP8038 PEHP6001 PEHP5033 PEHP9013 AECQ5980 AEDK0075 AEDK0707 AEDK0083 AEDK2953
Miscellaneous
Pocket Card "Electronic Diagnostic Codes" Chart "Practical Pressure Conversions" "Cleaning Rear Axle Housing Assemblies (785/789)" Training CD-ROM "Caterpillar Electronic Technician (ET) for Off-highway Trucks" Training CD-ROM "Truck Production Management System (TPMS) for Off-highway Trucks"
NEEG2500 SEES5677 SEBF8366 SERV7003 SERV7004
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TABLE OF CONTE CONTENTS NTS INTRODUCTION ................................................... ....................................................... .....................................................................7 ..............7 MAINTENANCE .................................................... ........................................................................................................... ...................................................................12 ............12 OPERATOR'S OPERA TOR'S ST STA ATION.............................................................. ..............................................40 MONITORING SYSTEM..........................................................................................................49 Messenger Display Module ................................................ ..................................................53 Advisor/VIMS Display ....................................................... .........................................................................................................64 ..................................................64 ENGINE......................................................................................................................................84 Engine Electronic Control System ...................................................... .......................................................................................85 .................................85 Engine Derates......................................................................................................................95 Engine Compression Brake ................................................ ................................................101 Cooling System...................................................................................................................106 Lubrication System.............................................................................................................108 Fuel System.........................................................................................................................109 Air Intake and Exhaust System ................................................ ..........................................117 POWER TRAIN ..................................................... ............................................................................................................. ..................................................................125 ..........125 Power Train Hydraulic System...........................................................................................127 Transmission Hydraulic System .................................................. .......................................134 Rear Axle ................................................ ........................................................ ............................................................................145 ....................145 Transmission/Chassis Transmission/Chas sis Electronic Control System.................................................. System .................................................. ............148 STEERING SYSTEM ..................................................... ............................................................................................................. .........................................................158 .158 HOIST SYSTEM ..................................................... ............................................................................................................ .................................................................173 ..........173 BRAKE SYSTEM ................................................... ....................................................... .................................................................193 ..........193 Brake Electronic Control System ............................................... ........................................221 Automatic Retarder Control System...................................................................................226 Traction Control System.....................................................................................................228 CONCLUSION.........................................................................................................................235 VISUAL LIST ........................................................ ................................................................................................................ ..................................................................236 ..........236 HYDRAULIC SCHEMATIC COLOR CODE.........................................................................239 HANDOUTS.............................................................................................................................240 POSTTEST .................................................... ........................................................................................................... ...........................................................................265 ....................265 POSTTEST ANSWER SHEET ................................................ ................................................269
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773F (EED)/775F (DLS) OFF-HIGHWAY TRUCKS INTRODUCTION
© 2007 Caterpillar Inc.
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INTRODUCTION
Shown is the right side of a 775F Truck. The hydraulic tank is located on the right side of the truck. The 773F/775F Trucks come standard with oil-cooled multiple disc brakes in the rear and caliper type disc brakes in the front. The major features added to the 773F/775F Trucks are: the new cab, the Messenger or VIMS Advisor monitoring system, the Tier 2 compliant C27 ACERT™ engine and cooling system, the ECPC transmission, and the hydraulic brakes. The Individual Clutch Modulation (ICM) transmission has been replaced with Electronic Clutch Pressure Control (ECPC) transmission. The Chassis/Transmission Electronic Control System controls most of the same functions as on the 773D/775D Trucks. The air system has been eliminated on the 773F/775F Trucks. The brakes are completely hydraulic.
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Some of the specifications of the 773F Truck are: - Serial No. Prefix: EED - Empty weight: 45200 kg (99650 lb) - Load carrying capacity: 54.4 tonnes (60 tons) - Gross Machine Weight (GMW): 100700 kg (222000 lb) - Length: 10.33 m (33.9 ft) - Width: 5.43 m (17.8 ft) - Height: 4.5 m (14.8 ft) - Gross Power 536 kW (719 hp) - Top speed, loaded: 63.6 km/h (39.5 mph) Some of the specifications of the 775F Truck are: - Serial No. Prefix: DLS - Empty weight: 46198 kg (101850 lb) - Load carrying capacity: 63.5 tonnes (70 tons) - Gross Machine Weight (GMW): 109770 kg (242000 lb) - Length: 10.33 m (33.9 ft) - Width: 5.43 m (17.8 ft) - Height: 4.5 m (14.8 ft) - Gross Power 582 kW (787 hp) - Top speed, loaded: 67.5 km/h (41.9 mph)
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Shown is the left side of a 775F Truck. The fuel tank is located on the left side of the truck.
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Shown is the front of a 775F Truck. The 773F/775F Trucks use a Next Generation Modular Radiator (NGMR). Its modular design, similar to the previous folded core radiator, permits easy removal of a single core without having to remove the entire radiator.
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Shown is the rear of a 775F Truck. The following two body options are available for the 773F/775F Trucks: - A dual-slope steel design with a "V" bottom main floor to reduce shock loading, center the load and reduce spills. - The dual-slope steel body above, with the addition of a rubber liner for increased resistance to impact and wear. All internal wear surfaces of the truck body are made with 400 Brinell hardness steel. The steel attachment body liner is also made with 400 Brinell hardness steel. The external components of the body are made of steel with a yield strength of 6205 bar (90000 psi). The rubber liner is one-fifth the density of steel, but absorbs impact four times better. The rear suspension cylinders absorb bending and twisting stresses rather than transmitting them to the main frame.
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MAINTENANCE
Before working on or operating the truck, read the Operation and Maintenance Manual thoroughly for information on safety, maintenance and operating techniques. Safety precautions and Warnings are provided in the manual and on the truck. Be sure to identify and understand all symbols before starting the truck. The first step to perform when approaching the truck is to make a thorough walk around inspection. Look around and under the truck for loose or missing bolts, for trash build-up and for coolant, fuel, or oil leaks. Look for indications of cracks. Pay close attention to high stress areas as shown in the Operation and Maintenance Manual.
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The following list identifies the items that must be serviced every 10 Hours or Daily. - Walk-Around Inspection: Check for loose or missing bolts, leaks, trash build-up, and cracks in frame structures and body support pads. - Back-up alarm: test
- Fuel tank: drain water/sediment
- Brakes, indicators, gauges: test
- Hoist and brake oil level
- Braking system: test
- Seat belt: inspect
- Coolant level
- Secondary steering: test
- Engine air filter service indicator
- Steering system oil level
- Engine oil level
- Transmission and torque converter oil level
- Fuel filter: drain water separator
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The front wheel bearing oil level is checked and filled by removing the plug (1) in the center of the wheel bearing cover. The oil should be level with the bottom of the plug hole. The fill plug is a magnetic plug. Inspect the fill plug weekly for metal particles. If any metal particles are found, remove the wheel cover and inspect the bearings for wear. When draining the oil, rotate the wheel so the drain plug (2) is at its lowest position. The service interval for changing the front wheel bearing oil is 500 hours. Use Final Drive and Axle Oil (FDAO) or commercial FD-1. As a substitute, Transmission Drive Train Oil (TDTO) with a commercial TO-4 may be used. Check the tire inflation pressure. Operating the truck with the wrong tire inflation pressure can cause heat build-up in the tire and accelerate tire wear. Caterpillar recommends inflating tires with dry nitrogen instead of air to reduce heat build-up and potential combustion. Nitrogen also slows rubber deterioration and rim corrosion. NOTE:
Care must be taken to ensure that fluids are contained while performing any inspection, maintenance, testing, adjusting, and repair of the machine. Be prepared to collect the fluid in suitable containers before opening any compartment or disassembling any component containing fluids. Refer to the "Tools and Shop Products Guide" (Form NENG2500) for tools and supplies suitable to collect and contain fluids in Caterpillar machines. Dispose of fluids according to local regulations and mandates.
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Check the front suspension cylinders for leaks or structural damage. Check the charge condition of the front suspension cylinders when the truck is empty and on level ground. Measure the charge height of the suspension cylinders and compare the dimension with the dimension that was recorded the last time the cylinders were charged. Recharge the cylinders with oil and nitrogen if necessary. A grease outlet fitting (arrow) is located on one side of each front suspension cylinder. The grease supply fitting is located on the opposite side of the suspension cylinder. No grease outlet fittings should be located on the same side of the suspension cylinder as the grease fill location. Having an outlet fitting on the same side of the suspension cylinder as the grease fill location will prevent proper lubrication of the cylinder. Make sure that grease is flowing from the outlet fittings to verify that the suspension cylinders are being lubricated and that the pressure in the cylinders is not excessive. NOTE:
For more detailed information on servicing the suspension system, refer to the Special Instruction "Suspension Cylinder Servicing" (Form SEHS9411).
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Inspect the brake linings (1) for wear. The thickness of the brake linings (not including carrier) must not be less than 3.15 mm (.125 in). Measure the lining at both ends because one end can wear more than the other. The clearance between the brake carrier guide pins (2) and the brake disc (3) must not be less than 1.5 ± 0.5 mm (.06 ± .02 in.).
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The primary fuel filter (1) is mounted between the right front wheel and the engine cooling fan. A reusable fuel/water separator mounts directly to the filter element. Periodically open the valve (2) under the separator bowl and drain any water into an approved container. After changing fuel filters, hold the switch (3) upward to activate the electric fuel priming pump to refill the fuel lines and filters with fuel.
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Dual engine oil filters (1) are located on the right front of the engine. Engine oil samples can be taken at the Scheduled Oil Sampling (S•O•S) tap (2) located on the front of the oil filter base. The secondary fuel filter (3) is located at the right front of the engine, in front of the engine oil filters. A fuel filter bypass switch (4) is located on the filter base. The bypass switch provides an input signal to the Engine ECM indicating if the filters are restricted. Jacket water coolant samples can be taken at the S•O•S coolant analysis tap (5). The coolant tap is located behind the engine oil filters.
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Shown are the hoist and brake hydraulic tank (1) and the torque converter and transmission hydraulic tank (2). Both tanks are equipped with oil level sight gauges. The oil level of both hydraulic tanks should first be checked with cold oil and the engine stopped. The level should again be checked with warm oil and the engine running. The lower sight gauge (3) on the hoist and brake hydraulic tank can be used to check the tank level when the hoist cylinders are in the RAISED position. When the hoist cylinders are lowered, the hydraulic oil level will increase. After the hoist cylinders are lowered, check the hydraulic tank oil level with the upper sight gauge (4). Check the lower converter and transmission oil sight gauge (5) with the engine off and the oil cold. Use the upper gauge (6) with the engine at idle and the oil warm. Inspect the hoist and brake hydraulic tank breather for plugging. Remove the breather cover (7) to access the hoist and brake tank breather. The converter and transmission breather (not shown) is located at the rear of the transmission. Inspect the condition of both hydraulic tank fill cap vents (located on top of the tanks) at regular intervals.
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When filling the hydraulic tanks after an oil change, fill the tanks with oil to the FULL COLD mark on the sight gauge. Turn on the engine manual shutdown switch so the engine will not start. Crank the engine for approximately 15 seconds. The oil level will decrease as oil fills the hydraulic systems. Add more oil to the tanks to raise the oil level to the FULL COLD mark. Crank the engine for an additional 15 seconds. Repeat this step as required until the oil level stabilizes at the FULL COLD mark. Turn off the engine manual shutdown switch and start the engine. Warm the hydraulic oil. Add more oil to the tank as required to raise the oil level to the FULL WARM mark. In both tanks, use only Transmission Drive Train Oil (TDTO) with a specification of TO-4 or newer. The following features are provided by TDTO TO-4 oil: - Provides maximum frictional capability required for clutch discs used in the transmission, torque converter, and brakes. - Increases rimpull because of reduced slippage. - Increases brake holding capability by reducing brake slippage. - Controls brake chatter. - Provides maximum frictional capability required for gears.
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The rear axles are equipped with planetary-type final drives. Rotate the final drive until the drain plug (1) is at the lowest position, as shown. The final drive oil level is checked and filled by removing the magnetic plug (2). The oil should be level with the bottom of the plug hole. Fill the rear axle housing with oil before filling the final drives with oil. Allow enough time for the oil to settle in all of the compartments. This can be as much as 20 minutes during cold temperatures. The oil is drained by removing the drain plug. The magnetic inspection plugs should be removed weekly from the final drives and checked for metal particles. For some conditions, checking the magnetic plugs is the only way to identify a problem which may exist. Use FDAO (Final Drive and Axle Oil) or Transmission Drive Train Oil (TDTO) with a specification of TO-4 or newer. These oils provide: - Maximum frictional capability required for gears - Increased lubrication capability for bearings NOTE:
The rear axle is a common sump for the differential and both final drives. If a final drive or the differential fails, the other final drive components must also be checked for contamination and then flushed. Failure to completely flush the rear axle after a failure can cause a repeat failure within a short time.
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Check the differential oil level by removing the magnetic inspection plug (1). The oil should be level with the bottom of the fill plug opening. Inspect the rear suspension cylinders for leaks or structural damage. Check the charge condition of the rear suspension cylinders when the truck is empty and on level ground. Measure the charge height of the suspension cylinders, and compare the dimension with the dimension that was recorded the last time the cylinders were charged. Recharge the cylinders if necessary. Inspect the condition of the rear axle breather (2) at regular intervals. The breather prevents pressure from building up in the axle housing. Excessive pressure in the axle housing can cause brake cooling oil to leak through the Duo-Cone seals in the wheel brake assemblies. NOTE:
For more detailed information on servicing the suspension system, refer to the Special Instruction "Suspension Cylinder Servicing" (Form SEHS9411).
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The body up retaining pins are stored inside a cross-tube (1) in a body support beam directly above the retaining bracket (2). When work is to be performed while the body is raised, the body up retaining pins must be installed through the holes in the body retaining bracket and the rear frame support (3) to hold the body in the raised position. The body is shown in the lowered position.
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The fuel tank is located on the left side of the truck. The fuel level sight gauge (1) is used to check the fuel level during the walk around inspection. A fuel level sender is located on the fuel level sight gauge. The fuel level sender provides input signals to the monitoring system, which informs the operator of the fuel level. Open the drain valve below the tank to remove condensation and sediment from the fuel tank. Inspect the condition of the fuel tank breather (above tank) and the fuel fill cap (2) at regular intervals. Fuel can be added at the attachment quick service fuel fill connector (3).
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The torque converter and transmission charging filter (1) is mounted to a bracket on the outside of the left frame rail in front of the fuel tank. Torque converter and transmission oil samples can be taken at the S•O•S tap (2). The oil filter bypass switch (3) provides input signals to the Transmission/Chassis ECM. The ECM sends a signal to the monitoring system in the cab to warn the operator when the filter is restricted. A pressure test port (4) is available for monitoring charge pressure for the torque converter and transmission circuits.
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The brake oil filter (1) is mounted to a bracket on the inside of the left frame rail. The brake filter includes an oil filter bypass switch (2) which provides input signals to the Brake ECM. An S•O•S port (3) can be accessed from below the machine.
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Before climbing the truck ladder, make sure that the manual engine shutdown switch (1) is OFF. The switch is located below the cab at the base of the left stairway. The engine will not start if the manual shutdown switch is ON. If necessary, the switch can be used to stop the engine from the ground level. The access light switch (2) is used to turn on or turn off the lighting in the area around the stairs. There is a second access light switch on the left side of the dash in the cab.
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While climbing the ladder, make a thorough inspection of the radiator. Be sure that no debris or dirt is trapped in the radiator cores. The battery disconnect switch is located under a cover (1) at the bottom of the right access ladder. If the machine is being parked for an extended period (overnight, etc.) turn off the disconnect switch and remove the key. The machine lockout and engine lockout switches are located behind an access cover (2) between the radiator cowling and the right stairway. The batteries are located inside the front bumper (3), at the base of the radiator cowling. Inspect the battery connections for corrosion or damage. Keep the battery terminals clean and coated with petroleum jelly. Inspect the electrolyte level in each battery cell, except maintenance free. Maintain the level to the bottom of the fill openings with distilled water.
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This illustration shows the engine disconnect switch (1) and the auxiliary start receptacle (2).
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The engine lockout control switch (1) allows the engine to be safely locked out while service is performed. The engine must be stopped to activate the engine lockout mode. When the engine lockout mode is activated, the following conditions exist: - The engine starter is disabled. - The secondary steering is disabled. - The prelube function is disabled. The following conditions must be met before the engine lockout mode will activate: - The transmission control must be in the PARK position. - The engine must be OFF. When the switch is activated, one of the following results will occur: - The indicator lamp (2) will illuminate continuously to indicate that the machine is in the engine lockout mode. - The indicator lamp will flash to indicate that the engine lockout mode will not activate until the transmission control is in the PARK position and the engine is OFF.
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The machine lockout control switch (3) allows the machine to be safely locked out while service is performed. When the machine lockout mode is activated, the following conditions exist: - The engine will start. - The transmission is disabled. - The hoist is disabled. - The steering is disabled. - The machine lockout mode indicator (4) will illuminate only after the start key is turned on. NOTE:
The lockout mode indicator on the dash panel will illuminate when the engine lockout control or the machine lockout control is activated.
Also located near the lockout switches are the following circuit breakers: - 90 Amp Alternator (5) - 15 Amp Engine (6) - 80 Amp Starter Solenoid (7)
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The coolant level on the 773F/775F is checked with the jacket water coolant sight gauge (1) located below the cab on the right side of the front cowling. Coolant is added by removing the radiator cap (2) located inside an access door on the upper deck. The water used in the cooling system is critical for good cooling system performance. Use distilled or deionized water whenever possible to prevent acids or scale deposits in the cooling system. Acids and scale deposits result from contaminants that are found in most common water sources. Never use water alone. All water is corrosive at engine operating temperatures without coolant additives. Also, water alone has none of the lubrication properties that are required for water pump seals.
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Cat trucks are filled at the factory with Extended Life Coolant (ELC). If ELC is maintained in the radiator, it is not necessary to use a supplemental coolant additive. Do not use a conventional coolant to top-off a system filled with Cat ELC. An acceptable substitute for ELC is a Cat DEAC (Diesel Engine AntiFreeze/Coolant) or a commercial heavy-duty coolant/antifreeze that meets ASTM D4985 or ASTM D6210 specifications.
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The steering system hydraulic tank is located on the right platform. Check the steering system oil level at the sight gauge (1), on the side of the tank. The steering system oil filter (2) cleans the oil before it enters the hydraulic tank. The steering system uses a pressure compensated piston-type pump mounted to the rear of the engine. Case drain oil from the steering pump returns to the steering tank through a case drain filter (3). Before removing the fill cap (4) to add oil to the steering system, depress the pressure release button (5) on top of the breather to release any pressure from the tank.
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The steering system filter base and the case drain filter base have bypass valves that allow the steering oil to bypass the filters if they are plugged. The engine oil level dipstick (6) and the engine oil fill tube (7) are located inside the access cover next to the steering oil tank. Check the engine oil level with the dipstick and add engine oil at the fill tube. Caterpillar recommends multigrade Diesel Engine Oil (DEO) with a specification of ECF-1. API CH-4, CI-4, and CI-4 Plus oils are only acceptable if they meet ECF-1 specifications. DEO oils with a CG-4 specification are acceptable, but should be limited to 250-hour oil change intervals. CF and older oils should not be used in Caterpillar diesel engines. Cat ECF-1 Specification was established by Caterpillar in 2003 and requires excellent soot dispersion, wear control, and piston deposit control.
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Shown are the air intake system components. Check the air filter restriction indicators (1). If the yellow piston is in the red zone, the air filters are restricted and must be serviced. The air filter housing covers serve as the precleaner assemblies. When servicing the filter elements, clean the precleaners (2) and dust valves (3) using air or water pressure, or detergent wash. The dust valve is OPEN when the engine is OFF and closes when the engine is running. The dust valve must be flexible and closed when the engine is running or the precleaner will not function properly and the air filters will have a shortened life. Two filter elements are installed in the filter housings. The large element is the primary element and the small element is the secondary element. Air intake system tips: - The primary element can be cleaned a maximum of six times. - Never clean the secondary element for reuse. Always replace the secondary element. - Air filter restriction causes black exhaust smoke and low power.
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To check the fluid level of the windshield washer reservoir, open the access door located at the left rear of the cab, behind the cab door. Open the filler cap (1) to check the fluid level and fill as necessary. To the left of the filler spout is the air conditioner filter (2). Clean or replace the filter element when a reduction of circulation in the cab is noticed.
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The remaining 10 Hours or Daily checks are performed in the operator's compartment: - Brakes: Check operation - Indicators and gauges: Test operation - Seat belt: Inspect - Back-up alarm: Test operation - Secondary steering: Test operation The service brakes are checked by depressing the pedal (1) and placing the shift lever in FIRST FORWARD. Accelerate the engine until the truck moves. The truck must not move below 1200 rpm. This procedure should be repeated to test the secondary brakes by depressing the secondary brake pedal (2). The cab air filter (3) is located inside the cab door, in the left-rear corner behind the trainer seat. Clean or replace the cab fresh air filter when necessary. NOTE:
Refer to the Operation and Maintenance Manual for information on the remaining tests performed in the cab.
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This illustration shows the cab air filter (1) located behind the trainer seat (2).
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OPERATOR'S STATION
Shown is a view of the 773F/775F operator compartment. The operator's station for the 773F/775F has been changed to improve operator comfort and ergonomics. The operator seat (1) is centered in the cab with the trainer's seat (2) positioned to the left. The hoist control lever (3) is now on the right console next to the transmission control lever (4). The 773F/775F is equipped with a standard Messenger Monitoring System or optional VIMS/Advisor Monitoring System (shown). The optional Caterpillar Work Area Vision System (WAVS) is a closed circuit video monitoring system. WAVS consists of a 178 mm (7 inch) LCD color display (5) and may include one, two, or three cameras. The display is mounted in the machine cab. The cameras are mounted on the frame of the machine. The location of the camera(s) is dependent on the machine type.
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The Truck Production Management System (TPMS) on the 773F/775F is controlled by a TPMS ECM if the machine is equipped with Messenger or a VIMS ECM if the machine is equipped with VIMS/Advisor. There are two sets of TPMS external loading lamps on the truck. One set of lamps is on the left side of the cab (arrow) and the other set is on the right platform. The lamps are green and red. The lamps inform the loader operator of the loading progress toward a target payload weight. The lamps are active only during the loading cycle and are off at all other times. During loading, the green (continue loading) lamps will be ON until the payload is 95% of the target weight setting. Then, the red (stop loading) lamp will light. A "last pass" indication can be programmed into the system. With last pass indication, the TPMS calculates an average loader pass size and predicts payload weight. If the predicted weight after the NEXT loader pass will be above 95% of the target weight setting, the red lamps FLASH. The red lamps will be ON continuously after the last pass (when fully loaded). A minimum of three loader passes are required for the "last pass" indication option to function correctly. The actual measured weight of the material in the truck body is displayed on the Messenger display or the VIMS/Advisor display.
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Located on the left side of the front dash panel are: - Telescopic/tilt steering column adjustment lever (1): Push for telescoping and pull for tilt. - Intermittent wiper/washer, turn signal control and dimmer switch (2). - Steering wheel mounted electric horn control (3). - Light switches and hazard warning switch (4). The instrument panel (5) includes a tachometer, four gauges, and several indicators that display the machine systems status. An LCD screen displays the service hour meter, machine ground speed, actual gear, and direction.
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Located on the right side of the steering column is the retarder lever (1). The retarder lever is used to modulate engagement of the service brakes. The retarder lever engages the rear brakes. The retarder lever can control the modulation of the service brakes more precisely than the service brake pedal located on the cab floor. Located on the dash to the right of the retarder lever are the key start switch (2), fan speed switch (3), temperature variable knob (4), air conditioner switch (5), and cigarette lighter (6). Above the HVAC controls is the Messenger display (7). Switches to the left of the Messenger display are the ARC ON/OFF switch (8), compression brake switch (9) (if equipped), and front brake switch (10).
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To the right of the operator's seat is the shift console which contains the transmission shift lever (1) and the hoist control lever (2). The 773F/775F truck has SEVEN speeds FORWARD and ONE REVERSE. The top gear limit and body up gear limit are programmable through the Transmission/Chassis ECM. The top gear limit can be changed from THIRD to SEVENTH. The body up gear limit can be changed from FIRST to THIRD. The 773F/775F truck hoist system is electronically controlled. The hoist control lever activates the four positions of the hoist control valve. The four positions are: RAISE, HOLD, FLOAT, and LOWER. A fifth position of the hoist valve is called the SNUB position. The operator does not have control over the SNUB position. The body up switch controls the SNUB position of the hoist valve. When the body is lowered, just before the body contacts the frame, the Transmission/Chassis ECM signals the hoist solenoids to move the hoist valve spool to the SNUB position. In the SNUB position, the body float speed is reduced to prevent hard contact of the body with the frame. The truck should normally be operated with the hoist lever in the FLOAT position. Traveling with the hoist in the FLOAT position will make sure the weight of the body is on the frame and body pads and not on the hoist cylinders. The hoist valve will actually be in the SNUB position.
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If the transmission is in REVERSE when the body is being raised, the hoist lever sensor is used to shift the transmission to NEUTRAL. The transmission will remain in NEUTRAL until: 1. the hoist lever is moved into the HOLD or FLOAT position; and 2. the shift lever has been cycled into and out of NEUTRAL. The hoist lever is also used to start a new TPMS cycle. NOTE:
If the truck is started with the body raised and the hoist lever in FLOAT, the lever must be moved into HOLD and then FLOAT before the body will lower.
The throttle backup and throttle lock switch (3), the WAVS alternate camera system switch (4) (if equipped), and a 12V power port (5) are also located on the shift console.
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The overhead console can be equipped with with three switches. The optional heated mirrors mirrors switch (1) controls the heated mirrors. The TCS test switch (2) is used to perform the TCS test when the switch is held. The brake release/secondary steering switch (3) manually activates the brake release and secondary steering pump when the switch is held.
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Located on the floor of the cab are the following pedals: - Secondary brake pedal (1): Used to modulate application of the parking brakes on the rear wheels. A position sensor is attached to the secondary secondary brake pedal that provides input signals to the Brake ECM. - Service brake pedal (2): The service brake pedal is used to modulate modulate engagement of the service brakes on all four wheels if the front brake ON/OFF switch is in the ON position. A position sensor is attached attached to the service brake pedal that provides input signals signals to the Brake ECM. - Throt Throttle tle pedal pedal (3): A throt throttle tle position position sensor is attached attached to the throt throttle tle pedal. pedal. The throttle throttle position sensor provides the throttle position input signals to the Engine ECM.
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Located behind the trainer's seat are the fuse fuse panels (1), the Cat ET service port (2), the TPMS or VIMS service port (3), the Product Link service port (4), a 12V power receptacle (5), and the 20 amp heater/air conditioner fan circuit breaker (6).
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MONITORI MONI TORING NG SYSTEM
The monitoring system on the 773F/775F Off-highway Trucks monitors various machine systems and then conveys the machine status to the operator. operator. The 773F/775F can be equipped with the standard monitoring system which includes a Messenger display module, or the optional monitoring system which includes a VIMS/Advisor display module. Both monitoring systems include an instrument cluster. cluster. The instrument cluster is a cab display that shows the operator the status of various machine parameters and alerts the operator of specific machine conditions. The ECMs and monitor monitor display modules communicate over the Cat Data Link. The display modules communicate with the instrument cluster over the Can Data Link. The monitoring system receives information from machine switches and sensors via the ECMs shown in this illustration of the Machine Electronic Control System. The 773F/775F can also have the following attachments: Minestar Minestar,, RAC, Product Link, Inclinometer, Telemetry antenna, and GPS antenna.
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The instrument cluster (1) and optional VIMS/Advisor display panel (2) are shown is this illustration. The standard Messenger module (not shown) is installed in the same same location as the VIMS/Advisor display panel. Problems from the machine systems are classified into four warning categories (1, 2, 2S, and 3) similar to other Caterpillar monitoring systems. During the normal operation mode and the menu mode, the Messenger or VIMS/Advisor display may be interrupted by a warning message. message. Warning messages are displayed when important instructions or information need to be displayed.
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Shown is the Instrument Cluster located in the center of the front dash panel. The Instrument Cluster includes 18 dash indicators, five analog gauges, and an LCD digital display (1). The LCD display window in the lower center of the dash includes the truck speed, gear, and direction on the top of the display and the service hour meter on the bottom of the display. The five parameters monitored by the analog gauges are: - Brake oil temperature (2) - Engine coolant temperature (3) - Engine speed (4) - Torque Converter oil temperature (5) - Fuel Level (6)
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This illustration shows the gauges and indicators on the instrument cluster.
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Messenger Display Module
The standard Messenger display module (1) is located in the right side of the front dash. The purpose of the Messenger is to display relevant machine information to the operator or service personnel. The Messenger display is used in conjunction with the instrument cluster to act as the monitoring system for the machine. The Messenger has a menu structure that allows the user to access the desired machine information. The default screen will display under normal machine operating conditions without any intervention from the operator or service personnel. The default screen of the Messenger module shows the shift lever and the gear position. The default screen is displayed at machine start-up and until the operator or the technician navigates to another screen. The Messenger consists of the display and four navigation buttons that are used to navigate through the menu structure. The button functions from left to right are as follows: Back (2): Used to navigate to the previous screen that was accessed in the Messenger. Left/Up (3): Allows the user to scroll left or up. Scroll direction is dependent on the specific data that is being displayed on the screen. Right/Down (4): Allows the user to scroll right or down. Scroll direction is dependent on the specific data that is being displayed on the screen. OK (5): Acts as a confirmation function for the Messenger.
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The Messenger Menu screen is divided into three sections. The top section identifies the name of the current menu. If the current name is split by a colon ":" then this indicates that the name after the colon ":" is the current menu and the name before the colon ":" is the parent menu of the current menu. The center section displays the current menu option that can be selected by pressing the OK button. The arrows at the left of the screen indicate whether you can scroll to the next screen to see further menu options. There are a total of five main menus that are available for navigation. Only one menu can be displayed at a time. The menus are accessed from the default menu by pressing the back arrow button. The five menus are: - Performance - Totals - Settings - Service - Service mode
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This illustration of a performance screen submenu shows the engine coolant temperature and shift lever position. A typical Messenger information screen normally displays the information in pairs. The headers at the top of the screen identify the information. The current values are displayed below the headers. The arrows at the left of the screen indicate whether you can scroll to the next screen to see additional information.
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The Performance menu allows the operator or technician to view two pages of information. These pages of information monitor vital machine system data during machine operation. This information can only be viewed. The Performance menu uses two screens to show the real time status of the information listed above on the right side of the illustration.
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The Totals main menu allows the operator or the technician to access information about the machine systems. The totals data can be used to determine when scheduled maintenance is required. The Totals menu shows accumulated values and includes two submenus. The two submenus are Payload and Machine. The Payload and Machine submenus display the information listed on the right side of the above illustration.
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Parameters are normally adjusted for specific operating conditions, operator preferences, and machine operating efficiency. The machine setup affects the parameters that are displayed. The attachments that are on the machine determine the software that is contained in the ECMs. Messenger looks at the software versions to determine the parameters that will be displayed and the parameters that will be variable. NOTE:
Cat ET can also be used to access the parameters.
The Settings menu allows the user to adjust the parameters for the following: - Messenger Display - Machine Identification - Transmission Operation - Brake Operation - Payload Operation - Engine Operation
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The Messenger Display parameters relate to the operator’s preferences for the Messenger display. The following parameters may be adjusted: - Language: Six standard languages (other languages available). - Units: Metric or English. - Contrast: Screen contrast. - Headlights On: Screen brightness with headlights ON. - Headlights Off: Screen brightness with headlights OFF. The Machine settings allow the user to set the machine serial number. The following parameters may be adjusted: - Product ID: Allows the user to set the machine serial number (password protected). - Equipment ID: Allows the name of the truck to be changed (password protected). The Transmission setting allows the following parameters to be adjusted: - Top Gear Limit: Allows the user to set the highest gear performance level. - Body Up Gear Limit: Adjusts the gear limit during truck operation when the body is raised. - Machine Speed Limit: Sets the highest truck speed. - Fuel Economy Mode: Allows the fuel usage to be changed. - Machine Overload Speed Limit: Limits transmission gear and engine speed when excessive payloads are detected (if machine is equipped with TPMS). The Brake setting allows the user to set the desired ARC speed and is password protected. The Payload menu allows the configuration of the Payload settings and is password protected. The Payload settings include the following: - Target Payload: Read and program the truck target payload. - Overload Limit: Read and program the percent overload. - Green TPMS Lamp: Read and program the installation of the green TPMS lamp. - Red TPMS Lamp: Read and program the installation of the red TPMS lamp. - Last Pass Enabled: Read and program the installation of the Last Pass indicator. The Last Pass indicator informs the shovel operator of the last load before the payload is over the rated load. The Engine setting allows the user to change the ether solenoid configuration to "No Ether Solenoid Installed" or "Continuous Flow" and is password protected.
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The Service menu allows the technician to access the machine parameters. The technician may also make selections for viewing or clearing logged events or codes. The Service menu will allow the technician to view data for the following systems: brake, steering, implement, and power train. The status of electronic components in the machine’s major systems can also be viewed. The Service menu option is displayed by selecting Service from the Main Menu. Press the Left/Up arrow button or the Right/Down arrow button until Service is displayed. Then press the OK button. The Service menu contains the following six submenus: - Diagnostic Events: Displays a complete list of all active and inactive event codes and diagnostic codes. - System Parameters: Allows the technician to view the status of system components. - Calibrations: Allows the technician to perform a payload calibration. The payload system must be calibrated if new TPMS software is installed or the suspension is charged. - System Tests: Allows the user to perform a transmission stall test or a system self test on the machine. - Systems Information: Allows the user to display information on all of the ECMs installed on the machine, such as ECM Part Number, etc. - Tattletale: The Messenger display module records the extreme value for each condition of the machine that is monitored.
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These illustrations show the information available within the Diagnostic Events menu. From the Service menu, use the appropriate arrow button to highlight the Diagnostic Events option and press the OK button to access the Diagnostic Events. Select the View Diagnostics display by pressing the OK button. The View Diagnostics option will display a complete list of codes (bottom left illustration). Each line on the list will show the following information: - SRC (Source ID) - CODE - OCC (Number of occurrences of the event or code) - ACT (if the code is active or inactive). Use the appropriate arrow button to highlight a diagnostic code or an event code on the list. Press the OK button to display the codes Detailed View (bottom right illustration). The Detailed View will display a text message that shows the following information: reporting ECM, failed component code, and explanation of the event.
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The technician can clear logged codes one at a time. Active codes are indicated with a mark under the "ACT" column. Active codes cannot be cleared until the faults have been corrected. To clear a code, access the Detailed View of the code, press the OK button and follow the prompts and directions. NOTE:
Only Level I and Level II codes may be cleared with Messenger. Messenger. When a code is cleared from Messenger, Messenger, the memory from the reporting ECM is cleared. The code is not cleared from from the Messenger ECM. Once the code has been cleared from from the reporting ECM, Messenger will update the code list. Messenger is an interface between the technician and the machine ECMs.
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The Service Mode Password menu is used to enter the Service mode. The Service Mode Password protects certain features from access by the operator. operator. Features that need to be protected from the operator can be b e enabled or disabled with a password. NOTE:
For more information on the Messenger Monitoring System, refer to the 773F, 775F,, 777F Off-highway Truck Monitoring Systems Operation, Tr 775F Troubleshooting, oubleshooting, Testing, and Adjusting Service Manual module (RENR8344).
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Advisor/VIMS Display
Shown above is the Advisor/VIMS graphical display module. It is located on the right right side of the dash. It is the operator and technician’s technician’s interface with the Advisor Monitoring System, including VIMS. Information is displayed on a backlit LCD display screen. The top portion of the screen is called the "Top Banner" and it displays vital machine information at all times. The Top Top Banner may display different information from machine to machine, depending on the model and the attachments that are installed. At the right of the display display screen is a column of five user user interface buttons. These buttons are used to navigate through the numerous Advisor screens, to make menu selections, or to enter data. The five buttons, buttons, from top to bottom, are: - LEFT/UP Arrow Button (1) - This button is used for screen navigation or data entry entry.. It can be used: • to scroll scroll up a vertical vertical list list or scrol scrolll left left across across a horizon horizontal tal list; list; • to decrease decrease a setti setting ng value, value, such such as decreasi decreasing ng brightnes brightness/cont s/contrast rast.. - DOWN/RIGHT DOWN/RIGHT Arrow Button Button (2) - This button button is also used for screen navigatio navigation n or data entry.. It can be used: entry • to scroll scroll down down a vertical vertical list list or scroll scroll right right across across a horizonta horizontall list; list; • to increase increase a setting setting value, value, such such as increas increasing ing brightnes brightness/cont s/contrast. rast.
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- BACK Button Button (3) - This button button is used: used: • to go up one one level in in a stair-s stair-step tep (hierarch (hierarchical) ical) menu structur structure, e, or to return return to to the previous screen; • as a backspace, backspace, or cancel cancel key key when the operat operator or or technici technician an wishes wishes to delete delete entered entered characters. - HOME Button (4) - This button is used to return return to the home menu screen, regardless of what screen is currently displayed. - OK Button Button (5) - This This button button is used: used: • to make make se sele lect ctio ions ns fro from m a scre screen en;; • to confirm confirm an entry entry, such as a password password,, or for saving saving an operator operator profile profile entry entry.. Navigation through the menus and sub-menus is accomplished by using the ARROW Buttons to highlight the desired selection, then pressing the OK Button. The ARROW Buttons are also used to highlight a mode or to set set a parameter. parameter. Pressing the OK Button selects that option. NOTE:
The left buttons are used to display a screen without scrolling. scrolling. If a screen is selected and one of the left buttons is pressed and held for at least three seconds, the screen is saved (programmed). (programmed). Whenever the button is pressed pressed again the "saved" screen will appear.
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Upon machine start-up (key ON), an introduction screen appears as shown in the top illustration and Advisor performs a self-test routine. After a few seconds the main screen screen will appear as shown in the bottom illustration. NOTE:
The time and date are set with VIMSpc software.
Also displayed to the right of the time and date is the inclinometer value.
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The illustration above shows a "pop-up" warning screen generated by the Transmission/Chassis ECM and reported by Advisor Advisor.. There may be more warning screens if there there are any other active faults or events reported to Advisor by the Transmission/Chassis ECM, or any other ECM on the machine. Advisor will scroll through all of the warning screens generated by all of the active faults and events. Each of these warning warning screens must be individually acknowledged by pressing the "OK" button. Each of these warning screens contains the following information: - The reporting reporting ECM (in (in text) - The reporting MID (module identifier, identifier, or ECM code) - The ID (Component ID and Failure Mode Identifier) - A text messag messagee stating stating the the failed failed component component - A text message message stating stating the failur failuree mode of the component component - A prompt for the the operator operator to acknowled acknowledge ge the warning warning Acknowledging these warnings does not clear them from the reporting ECM's memory, but only clears them from the screen, screen, or "snoozes" them. The warnings remain an active event or fault until the problem is resolved. Advisor will display the the message again after a pre-determined amount of time, depending on the severity of the event.
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Advisor’s menu structure structure is arranged in a stair-step, stair-step, or hierarchical list format. When the operator or technician selects an option from a menu or list, the resulting screen is one level down from that selection. More selections, or options, may be available from that screen as well. There may also be more than one page of information information or options to be displayed from any level. This is indicated by the "More Options" icon, which may point left, point right, point up, or point down, depending upon how the data or list is arranged. The illustration above shows the options that are available from Advisor's Home Menu screen. The Home Menu screen and its options will be displayed upon pressing the HOME button from any screen within Advisor. Advisor.
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The Operator menu allows the user to perform the following: - Sel Select ect a profil profilee - Cre Create ate a profi profile le - Del Delete ete a profi profile le - View/s iew/save ave a current profile profile - Factor Factory y Set (recalls default default settings) settings) The profile of an operator is a saved set of preferences that is identified by a name. Once the profile is created, the operator may associate various display settings and settings for the power train to that profile. After all of the parameters have been adjusted to the operator's preference, the operator may then save the parameters for future use.
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This illustration shows the options within the Operator Menu.
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The Service menu contains six submenus. The following is a list of the submenus: - Diagnostics - Calibrations - System Information - Tattletale - System Tests - Service Parameters
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This illustration shows the diagnostics submenu within the service menu. The Active Events menu option shows the ECM and the service hours for each event. The following list is of information that is displayed for the active event: - Electronic Control Module - Event Code - Date of occurrence - Time of occurrence - Warning Level - Number of occurrences The Logged Events menu option shows the list of events and diagnostic codes that have been recorded. Logged events can only be cleared by downloading and resetting the VIMS ECM with VIMSpc. The Trigger Snapshot menu option allows the user to manually initiate a snapshot of the system in addition to the snapshots that are already programmed. The snapshot will remain active until the time has elapsed.
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The Data Logger Start menu option allows the user to initiate the data logger. If the information for the data logger is being downloaded from the machine, the data logger cannot be started. The operator can initiate and stop the data logger numerous times until the total time for logging the data is thirty minutes. The Data Logger Reset menu option allows the user to reset the data logger, which clears all of the logged information. Thirty minutes will be available after the data logger has been reset. NOTE:
The Data Logger is the only onboard file that can be reset through the Advisor display. The Advisor must be either in the Service Mode or Cat ET must be connected to the data link to reset the data logger. The VIMSpc software is not needed to reset the data logger.
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These illustrations show four of the submenus within the service menu. The Calibrations option consists of the Truck Payload and Inclinometer calibrations. The System Information menu option allows the user to view the information for the following machine ECMs: - Advisor - Engine - Transmission/Chassis - Brake - VIMS The ECM information contains the following: - ECM serial number - Software part number - Software release date - Software description
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The following options are available under the tattletale menu: - Active - Brake Oil Temperature - Engine Coolant Temperature - Engine Speed - Torque Converter Temperature - Fuel Level The Active option will display the tattletale value for each gauge. The five specific options will display the tattletale value for the gauge that is specified. NOTE:
The tattletale is password protected. The value for each gauge is protected from being cleared.
The System Tests option will allow the technician to perform the Stall Diagnostic Test or the Self Test. The instrument cluster will initiate a self test when the key start switch is moved to the START position. The gauge needles will move to the maximum right position for 0.5 seconds and then return to the minimum left position. This action prevents the gauge needles from circling to the bottom side of the gauge if the display is inverted.
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This illustration shows the Service Parameters submenu within the service menu. The following Service Parameters options will be displayed: - Sort By ECM - Sort By Type - All Parameters The Sort By ECM menu option allows the user to view the parameters that are associated with each ECM. All of the parameters for the specific ECM are listed. The following ECMs can be selected: - Advisor - Engine - Transmission/Chassis - Brake - VIMS
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The Sort By Type menu option allows the user to view the parameters that are associated with different components. The following types of parameters can be chosen: - Temperatures - Pressures - Speeds - Filter Switches - Operator Inputs - Sensor Duty Cycles - Totals The All Parameters menu option allows the user to view the entire list of parameters.
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The Settings menu allows the user to view the following parameters which are the same parameters as the Messenger Settings menu: - Display Setup - Machine - Transmission/Chassis - Brake - VIMS (same as Messenger Payload submenu) - Engine
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The Display Setup parameters relate to the operator’s preferences for the Advisor display. The following parameters may be adjusted: - Language (same as Messenger) - Units (same as Messenger) - Contrast (same as Messenger) - Headlights On (same as Messenger) - Headlights Off (same as Messenger) - Date format: (Advisor only) - Time format: (Advisor only) The Machine setting allow the user to set the machine serial number. The following parameters may be adjusted and are the same as the Messenger Display: - Product ID - Equipment ID The Transmission/Chassis setting allows the following parameters to be adjusted: - Top Gear Limit (same as Messenger) - Body Up Gear Limit (same as Messenger) - Machine Speed Limit (same as Messenger) - Fuel Economy Mode (same as Messenger) - Machine Overload Speed Limit (same as Messenger) - Load Count (Advisor only) The Brake setting is the same as the Messenger display. The VIMS/Payload menu allows the configuration of the Payload settings and is password protected. The following payload settings are the same as the Messenger Display: - Target Payload - Overload Limit - Green TPMS Lamp - Red TPMS Lamp - Last Pass Enabled The Engine setting allows the user to change the ether solenoid configuration to "No Ether Solenoid Installed" or "Continuous Flow" and is the same as the Messenger Display.
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The Payload menu option is entered by selecting Payload from the Main menu. The Payload menu option allows the user to view the information for the payload. The user can view the following information: - Target for the payload - Calculated gauge for the payload
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The Monitor menu option allows the user to view four parameters. The navigation button is used to select the parameter or view a different parameter. Press the OK button to obtain a list of available parameters.
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The Grade menu option allows the user to view the grade of the hill. The user can view the following information: - Percentage of the grade value - Image of the truck that represents the grade
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The Service Mode menu option allows the user to enable and disable the service mode. The password entry screen will appear if the password has been entered in Cat ET. The Advisor will enter the Service Mode after the password has been entered correctly. NOTE:
For more information on the Advisor/VIMS Monitoring System, refer to the 773F, 775F, 777F Off-highway Truck Vital Information Management System (VIMS) Systems Operation, Troubleshooting, Testing, and Adjusting Service Manual module (KENR5955).
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ENGINE
Shown is the C27 engine with ACERT™ Technology used in the 773F/775F Off-Highway Trucks. The engine performance specifications for the 773F Truck are:
The engine performance specifications for the 775F Truck are:
Serial No. Prefix:
EHX
Serial No. Prefix:
LJX
Performance Spec:
0K5975
Performance Spec:
0K5979
Gross Power:
536 kW (719 hp)
Gross Power:
587 kW (787 hp)
Full Load rpm:
2000
Full Load rpm:
2000
High Idle rpm
2200
High Idle rpm
2200
Low Idle rpm
800
Low Idle rpm
800
Max Torque rpm
1300
Max Torque rpm
1300
Overspeed rpm
2800
Overspeed rpm
2800
This V-12 engine uses twin turbochargers, Air to Air AfterCooler (ATAAC) and Mechanical Electronic Unit Injection (MEUI) for power, reliability and fuel economy. The C27 is compliant with U.S. EPA Tier 2 and European Union Stage II emissions regulations.
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Engine Electronic Control System
Shown is the electronic control system component diagram for the C27 engine used in the 773F/775F Truck. Fuel injection is controlled by the Engine Electronic Control Module (ECM). Many electronic signals are sent to the Engine ECM by sensors, switches, and senders. The Engine ECM analyzes these signals and sends signals to various output components. Output components can be relays, lamps, other controls, or solenoids. For example, based on the various input signals, the Engine ECM determines when and for how long to energize the injector solenoids. When the injector solenoids are energized determines the timing of the engine. How long the solenoids are energized determines the engine speed.
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Fuel injection and some other systems are controlled by the Engine ECM (1) located at the front of the engine. Other systems controlled by the Engine ECM are: ether injection, engine start function, engine oil pre-lubrication, variable speed Rockford fan, engine retarding, and engine derate. The Engine ECM has two main connectors for diagnostics. The larger 120-pin connector (2) known as J2 connects to the engine harness. The smaller 70-pin connector (3) is identified on schematics as J1 and connects to the machine harness. A 2-pin timing calibration connector is located to the right of the ECM. If the engine requires timing calibration, a timing calibration sensor (magnetic pickup) is installed in the flywheel housing and connected to the timing calibration connector. Using the Caterpillar ET (Cat ET) service tool, timing calibration is performed automatically for the speed/timing sensors. This step is performed to avoid instability and ensures that no backlash is present in the timing gears during the calibration process. Timing calibration improves fuel injection accuracy by correcting for any slight tolerances between the crankshaft, timing gears, and timing wheel. Timing calibration is normally performed after ECM replacement, cam or crank sensor replacement, or timing wheel replacement. Occasionally, Caterpillar will make changes to the internal software that controls the performance of the engine. These changes can be performed by using the WinFlash program in Cat ET. Cat ET is used to diagnose and program the electronic controls used in Off-highway Trucks. If using the WinFlash program, a "flash" file must be obtained from Caterpillar and uploaded to the ECM.
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The coolant temperature sensor (1) is located on top of the engine toward the front left side. The coolant temperature sensor is an analog sensor that is monitored by the Engine ECM. When the coolant temperature is too high, the Engine ECM will signal the monitoring system to display a warning. The Engine ECM also uses the coolant temperature sensor information for cold mode functions such as timing changes, elevated idle, cold cylinder cut-out, and ether injection. The intake air temperature sensor (2) is located on top of the engine toward the front right side. The intake air temperature sensor is an analog sensor that is monitored by the Engine ECM. The ECM monitors intake air temperature for derating the engine at high temperatures, for engine shutdown at high temperatures, and for signaling the monitoring system in the event of a problem. NOTE:
If a high temperature event is severe enough, the monitoring system will issue a Level 3 warning. The operator must park the machine as soon as possible. When the Engine ECM determines that the ground speed is zero and the transmission is in PARK, the engine will automatically shut down.
The turbo outlet pressure sensor (3) is used for calculating boost. The atmospheric pressure sensor (4) is located on top of the engine toward the front right side. The atmospheric pressure sensor is an analog sensor that is monitored by the Engine ECM. The ECM monitors atmospheric pressure for the following: altitude derate, air inlet restriction derate, and calibration reference for other sensors.
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The crankshaft speed/timing sensor (1) is located on the lower left of the engine toward the front side. The crank sensor measures engine speed and timing for control of the timing and delivery of fuel to each of the engine's cylinders. Sensing engine speed allows engine speed governing, fuel limiting, and fuel injection timing. If the crank speed/timing sensor fails, the cam speed/timing sensor allows for continuous operation. The oil pressure sensor (2) is located on the left side of the engine. The oil pressure sensor is an analog sensor that is monitored by the Engine ECM. When the oil pressure is too low, the Engine ECM will signal the monitoring system to display a warning. The ECM will also log an event that requires a factory password to clear.
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The cam speed/timing sensor (arrow) is located on the right side of the engine at the back of the timing gear housing behind the primary fuel filter. The cam sensor is used as a back-up for the crank speed/timing sensor. If the crank speed/timing sensor fails, the cam speed/timing sensor allows for continuous operation.
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The engine will start and run when only one sensor signal is present from either the crank or cam sensor. During engine operation, if both speed/timing sensors fail, the Engine ECM will stop fuel injection and the engine will shut down. During start-up, the loss of both sensors will prevent the engine from starting. If the engine is running and the signal from the crank speed/timing sensor is lost, a slight change in engine performance will be noticed when the Engine ECM performs the changeover to the cam speed/timing sensor. If the signal from the crank speed/timing sensor is not present during start-up, the engine will start normally. Loss of the cam speed/timing sensor during engine operation will not result in any noticeable change in engine performance. However, if the signal from the cam speed/timing sensor is not present during start up, the engine may require a slightly longer period of time to start and may run rough for a few seconds until the ECM determines the proper firing order by using only the crank engine speed/timing sensor.
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Text Reference
The teeth configuration in the crankshaft timing wheel are not the same as the camshaft timing wheel. The camshaft timing wheel includes 37 timing teeth with 36 of the teeth spaced equally at 10° apart. One tooth is spaced 5° apart from the other teeth. There are only 35 teeth on the crankshaft gear spaced equally at 10° apart. Two of the teeth are spaced at 20° apart, which creates a "gap" in the gear teeth. When the Engine ECM uses the cam speed sensor to determine timing for engine starting, the ECM knows exactly what cylinder is at TDC. The following cylinders are at TDC at the same time (one cylinder bank only): - Cylinder No. 1 (compression stroke) and No. 6 (exhaust stroke) - Cylinder No. 2 (compression stroke) and No. 5 (exhaust stroke) - Cylinder No. 3 (compression stroke) and No. 4 (exhaust stroke) When the Engine ECM uses the crank speed sensor to determine timing for engine starting, the ECM does not know which of the two cylinders is at TDC. As an example, the Engine ECM will attempt to fire cylinder No. 1 and check if there is any increase in the engine RPM. If there is no increase in rpm, the ECM determines that the TDC timing position at that firing moment is cylinder No. 6. This action may result in a longer engine start time.
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Located behind the right pedal, the throttle position sensor (arrow) provides the desired throttle position to the Engine ECM. If the Engine ECM detects a fault in the throttle position sensor, the throttle back-up switch in the cab can be used to increase the engine speed to 1300 rpm. The throttle position sensor receives a regulated 8.0 ± 0.5 Volts from the Engine ECM. The throttle position sensor output signal is a Pulse Width Modulated (PWM) signal that varies with throttle position and is expressed as a percentage between 0 and 100%. To check the output signal of the throttle position sensor, connect a multimeter between Pins B and C of the throttle position sensor connector. Set the meter to read "Duty Cycle." The duty cycle output of the throttle position sensor should be: - Low Idle: 16 ± 6% - High Idle: 85 ± 4%
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1
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The pre-lubrication (QuickEvac) pump (1) is located on the end of the secondary steering/brake release pump and motor assembly (2). The pump and motor assembly is now located on the front of the front frame crossmember. The engine oil pre-lubrication QuickEvac pump is controlled by the Transmission/Chassis ECM. The Transmission/Chassis ECM energizes the pre-lubrication pump relay located behind the cab. The relay behind the cab then energizes the prelube relay on the left frame. The QuickEvac mode is used to allow the technician to quickly evacuate the oil for an oil change. The QuickEvac mode can only be performed when the engine lockout is activated. Engine starting and pre-lubrication functions are also inhibited when the engine lockout is activated.
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If the truck is equipped with an ether start system, the Engine ECM will automatically inject ether from the ether valve (arrow) and ether cylinder during cranking. The amount of automatic ether injection depends on the engine oil or jacket water coolant temperature. The Engine ECM sends a duty cycle signal to the ether injection relay. The maximum duty cycle is 50%. A 50% duty cycle will pulse the ether relay ON three seconds and OFF three seconds. The maximum ether delivery is ten 3-second shots per minute. Each shot delivers 6 ml (0.2 oz) of ether. The Engine ECM will energize the ether injection relay only if: - Engine intake manifold air temperature is below a certain temperature. - Engine coolant temperature is below a certain temperature. Cat ET can be connected to the machine to turn the ether injection system ON or OFF.
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Engine Derates
The coolant temperature sensor measures the temperature of the coolant. When the temperature of the coolant exceeds 110° C (230° F), the Engine ECM will initiate a Level 1 Warning. When the temperature of the coolant exceeds 111° C (231° F), the Engine ECM will initiate a Level 2 Warning. At 111° C (231° F) the Engine ECM will initiate a 25% derate. Refer to the illustration for the remainder of the high engine coolant temperature derates. At 100% derate, the engine available power will be approximately 50%.
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The intake manifold air temperature sensor measures the temperature of the air that is flowing to the intake manifold. The sensor is used to initiate warning levels and engine derates. After the engine is running for at least 3 minutes and if the intake manifold air temperature goes above 82° C (180° F), the Engine ECM will initiate a Level 1 Warning. After the engine is running for at least 3 minutes and if the intake manifold air temperature goes above 86° C (187° F), the Engine ECM will initiate a Level 2 Warning. With the Level 2 Warning, the Engine ECM signals the engine to initiate a 3% derate. This derate will have a 20% upper limit.
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This illustration shows a graph with the two different warning levels for low oil pressure and the low oil pressure derate. When the oil pressure is below the blue line (154 kPa @ 1600 rpm) (22 psi @ 1600 rpm), the Engine ECM will enable the low oil pressure Level 1 Warning. Change machine operation or perform maintenance to the system in the event of a warning. When the oil pressure is below the red line (104 kPa @ 1600 rpm) (15 psi @ 1600 rpm), the Engine ECM will enable the low oil pressure Level 3 Warning. The operator should immediately perform a safe engine shutdown in the event of a Level 3 Warning. Also, with the Level 3 Warning the Engine ECM initiates a 35% engine derate. If the signal between the Engine ECM and the oil pressure sensor is lost or disabled, the Engine ECM will initiate a low engine oil pressure Level 1 Warning.
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The air inlet restriction is the pressure difference between the turbo inlet pressure sensor and the atmospheric sensor. The turbo inlet pressure sensor measures the air inlet pressure at the turbocharger compressor housing. As the air restriction increases, the pressure difference will increase. If the engine has been running for over 4 minutes and the air inlet restriction is 7.5 kPa (30 in. of water) for 30 seconds, the Engine ECM will initiate a Level 1 Warning. If the air restriction increases to 9.0 kPa (36 in. of water) for 30 seconds or the turbo inlet pressure sensor fails, then a Level 2 Warning will occur and the engine will enter the air inlet restriction derate. When the pressure difference between the turbo inlet pressure sensor and the atmospheric sensor reach a difference of 10.0 kPa (40 in. of water), the Engine ECM will derate the engine approximately 2%. The Engine ECM will then derate the engine 2% more for every 1 kPa difference up to 20%.
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This illustration shows the graph for the warning and the derates map for the fuel temperature. When the fuel temperature exceeds 90° C (194° F), the Engine ECM will activate a Level 1 Warning. When the fuel temperature increases to 91.0° C (196° F) a Level 2 Warning will be initiated by the Engine ECM. At the same time, the engine will derate to 12.5%. If the fuel temperature exceeds 92° C (198° F), the engine will be derated to 25%. A fuel temperature sensor open circuit will derate the engine to 12.5%. Excessive fuel temperature will cause injector wear.
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When the differential pressure switch recognizes a fuel pressure of 138 kPa (20 psi) for 1 hour, the Engine ECM will initiate a Level 1 Warning. When the differential pressure switch recognizes 138 kPa (20 psi) across the filter for 4 hours, the Engine ECM will initiate a Level 2 Warning. With the Level 2 Warning initiated, a 35 % derate is applied to the engine. This feature will be disabled when the fuel temperature is below 30° C (86° F).
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Engine Compression Brake
The 773F/775F Trucks can be equipped with the optional engine compression brake. The compression brake provides higher downhill travel speeds and reduces brake wear in addition to the Automatic Retarder Control (ARC) system. The compression brake uses a master/slave hydraulic actuation system to open exhaust valves on the compression stroke which releases pressurized air and creates a net braking force at the flywheel. The compression brake assembly, as shown in this illustration, controls two cylinders. The compression brake assembly is mounted to the rocker arm shaft supports below the engine valve covers. The compression brake is pressurized with engine oil from the rocker arm shaft and uses a solenoid valve to control oil flow in the brake housing. The compression brake is activated by a signal from the Engine ECM to the solenoid valve (1). As the fuel injector rocker arm pushes up on the master piston (2), the corresponding slave piston (3) is pressurized to push down on the exhaust valve bridge, decompressing the cylinder and preventing the normal power stroke. On the C27 engine, up to six brake assemblies are used. The control circuit for the compression brake permits the operation of either two, four, or all six of the compression brake assemblies which provides progressive braking capabilities with the retarding effect of four, eight, or all 12 of the engine cylinders. Compression brake system service consists of only periodic valve lash checks.
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This illustration shows the oil flow in the C27 engine compression brake. Oil from the engine oil pump flows through the rocker arm shaft oil passage. The compression brake solenoid valve controls the oil flow in the compression brake hydraulic circuit. When the Engine ECM energizes the solenoid, oil flows through the check valves to the slave pistons and the master pistons. Oil pressure overcomes spring force and the master piston moves down and contacts the fuel injector rocker arm. The master piston will follow the movement of the fuel injector rocker arm. As the fuel injector rocker arm moves up the master piston moves up and causes the oil to close the check valve. With the check valve closed, oil pressure increases in the compression brake hydraulic circuit and the slave piston is forced down. The slave piston makes contact with the exhaust valve rocker arm and causes the exhaust valve to open. As the exhaust valve opens, the engine cylinder pressure is relieved through the open exhaust valve, which creates a net braking force at the flywheel.
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When the fuel injector rocker arm moves down, the master piston moves down and the hydraulic pressure decreases. The exhaust valves are returned to the closed position by the exhaust rocker arm. The check valve opens and relieves the oil pressure. When the Engine ECM de-energizes the compression brake solenoid, oil is drained from the slave and master pistons to the tank. The exhaust valves close and the slave piston returns to the starting position.
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Text Reference
ENGINE COMPRESSION BRAKE SCHEMATIC
Left Bank Valve Cover Entry Connector Compression Brake Solenoid 1 and 3
Compression Brake Solenoid 9 and 11
Compression Brake Solenoid 5 and 7
10 11 12
J700-BR J701-GN K739-BU
Engine ECM P2/J2 5 3 14
Compression Br ake Med / Hi Compression Brake Low / Hi Compression Brake Return
8 1
Compression Br ake Med / Hi Compression Brake Low / Hi
Right Bank Valve Cover Entry Connector Compression Brake Solenoid 10 and 12
Compression Brake Solenoid 2 and 4
Compression Brake Solenoid 6 and 8
10 11 12
K737-BR K738-GN K739-BU 892-BR 893-GN
P1/J1 9 Cat Data Link 8 Cat Data Link +
Brake ECM P1/J1 893-GN 892-BR 772-BR A235-BK
Compression Brake Enable Switch
10 20 34 45
Cat Data Link + Cat Data Link Compression Br ake Enable Sensor Return
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This illustration shows the wiring and components of the engine compression brake. When the compression brake switch in the cab is activated, the Brake ECM sends a signal to the Engine ECM via the Cat Data Link. The Engine ECM controls the compression brake solenoids to slow the machine. The Engine ECM provides three levels of braking: LOW, MEDIUM, and HIGH. When the ECM commands a LOW braking level, two solenoids (one on each valve bank) will activate the compression brake for four cylinders (5, 7, 6, and 8). When the ECM commands a MEDIUM braking level, four solenoids (two on each valve bank) will activate the compression brake for eight cylinders (5, 7, 6, 8, 9, 11, 2, and 4). When the ECM commands a HIGH braking level, six solenoids (three on each valve bank) will activate the compression brake for all 12 cylinders.
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This chart shows an example of the ARC and engine compression brake levels in a one minute period during a drive cycle. When the machine speed exceeds a pre-determined speed, the ARC system is activated to slow the machine. If further braking is required, the Engine ECM will command the engine compression brake to the LOW, MEDIUM, or HIGH brake level setting as necessary to slow the machine.
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Cooling System
The jacket water cooling system on the 773F/775F uses a Next Generation Modular Radiator (NGMR). The NGMR (arrow) is a single-pass flow design, replacing the two-pass flow folded core system. The coolant enters at the top left and flows out at the bottom right, similar to an automotive design. Being modular, individual cores may be removed for service while the radiator remains in place.
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COOLING SYSTEM FLOW Thermostat Housing
Radiator
Engine Block
99 ATA AC
Engine Oil Cooler Brake Oil Cooler Transmission and Torque Converter Oil Cooler
Water Pump
Jacket water coolant flows from the water pump (1) through the engine oil cooler (2), through the brake oil cooler (3), and the transmission and torque converter oil cooler (4) to both sides of the engine cylinder block. Coolant flows through the engine block to the cylinder heads. From the cylinder heads, the coolant flows to the two temperature regulators and, based on coolant temperature, either flows to the radiator (if hot) or through the bypass tube (5) to the water pump (if cold) to recirculate until the engine reaches operating temperature. The thermostats are located in the thermostat housing (6) at the top of the bypass tube. The bottom illustration shows a schematic of the coolant flow.
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Lubrication System
The engine oil pump draws oil from the oil pan through a screen. Oil flows from the pump through an engine oil cooler bypass valve to the engine oil cooler. The bypass valve for the engine oil cooler permits oil flow to the system during cold starts when the oil is thick or if the cooler is plugged. Oil flows from the engine oil cooler to the oil filters. The oil flows through the filters and enters the engine cylinder block to clean, cool, and lubricate the internal components and the turbochargers.
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Fuel System
The fuel tank is located on the left side of the truck. Fuel is pulled from the tank through the primary fuel filter by the fuel transfer pump. Priming is now done electrically using a switch (arrow) located above the primary fuel filter. A reusable fuel/water separator mounts directly to the bottom of the fuel filter.
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The fuel transfer pump (arrow) is located at the top rear of the engine. The fuel transfer pump contains a bypass valve to protect the fuel system components from excessive pressure. The bypass valve setting is higher than the setting of the fuel pressure regulator. Fuel flows from the transfer pump to the secondary fuel filter located on the right side of the engine.
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The differential fuel pressure switch (1) is located in the top of the secondary fuel filter housing on the right side of the engine. This switch will indicate a restriction in the fuel filter. A warning will be sent by the Engine ECM to the monitoring system. The fuel pressure sensor (2) is located in the top of the secondary fuel filter housing, directly behind the differential pressure switch. This sensor is used to monitor fuel pressure. The engine fuel temperature sensor (3) is located in the top of the secondary fuel filter housing, behind the other two sensors. The Engine ECM uses the fuel temperature measurement to make corrections to the fuel rate and maintain power regardless of fuel temperature (within certain parameters). This feature is called "Fuel Temperature Compensation."
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Fuel flows from the secondary fuel filter base through the hoses (1) to the MEUI fuel injectors. Return fuel from the injectors flows through the fuel pressure regulator (2) before returning to the fuel tank. Fuel pressure is controlled by the fuel pressure regulator. Fuel pressure should be between 420 and 840 kPa (61 and 122 psi) at Full Load rpm.
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The 773F/775F now has a fuel cooler (arrow). The fuel cooler is located in front of the radiator and below the aftercooler core. Fuel flows from the fuel regulator, through the fuel cooler, and to the tank.
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Fuel is pulled from the tank through the primary fuel filter by the fuel transfer pump. Fuel flows from the transfer pump to the secondary fuel filter. Fuel flows from the secondary fuel filter base through the fuel injectors in the cylinder heads. Return fuel from the injectors flows through the fuel pressure regulator and fuel cooler before returning to the tank. The electric fuel priming pump is used to fill the filters after they are changed.
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When an injector is replaced, the injector trim codes must be retrieved and installed in the Engine ECM. The trim code files are located on a CD that comes with the new injector or can be obtained from the Service Information System (SIS). Access the trim code files from the Cat ET Service menu as shown in the illustration.
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Select the injector trim file from either the CD or from the appropriate directory on the computer if the trim file was obtained from SIS.
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Air Intake and Exhaust System
Shown are the air intake system components. Check the air filter restriction indicators (1). If the yellow piston is in the red zone, the air filters are restricted and must be serviced. When servicing the filter elements, clean the precleaners (2) and dust valves (3) using air or water pressure, or detergent wash. The dust valve is OPEN when the engine is OFF and closes when the engine is running. The dust valve must be flexible and closed when the engine is running or the precleaner will not function properly and the air filters will have a shortened life. Two filter elements are installed in the filter housings. The large element is the primary element and the small element is the secondary element. Air intake system tips: - The primary element can be cleaned a maximum of six times. - Never clean the secondary element for reuse. Always replace the secondary element. - Air filter restriction causes black exhaust smoke and low power.
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There is a turbocharger inlet pressure sensor (1) located in the tube between the air filters and the turbochargers. This illustration shows the inlet pressure sensor from above, looking behind the fresh air inlets (2) above the air filter canisters. The Engine ECM uses the turbocharger inlet pressure sensor in combination with the atmospheric pressure sensor to determine air filter restriction. The ECM provides the input signal to the monitoring system, which informs the operator of the air filter restriction. As the air restriction increases, the pressure difference will increase. If the engine has been running for over 4 minutes and the air inlet restriction is 7.5 kPa (30 in. of water) for 30 seconds, the Engine ECM will initiate a Level 1 Warning. If the air restriction increases to 9.0 kPa (36 in. of water) for 30 seconds or the turbo inlet pressure sensor fails, then a Level 2 Warning will occur and the engine will enter the air inlet restriction derate. When the pressure difference between the turbo inlet pressure sensor and the atmospheric sensor reach a difference of 10.0 kPa (40 in. of water), the Engine ECM will derate the engine approximately 2%. The Engine ECM will then derate the engine 2% more for every 1 kPa difference up to 20%.
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The C27 engine is equipped with two turbochargers, one on each side. Each turbocharger is driven by the exhaust gas from the cylinders which enters the turbine side (1) of the turbocharger from the exhaust manifold. The exhaust gas flows through the turbocharger, spinning the turbine wheel, then exits to the exhaust piping and muffler. The clean air from the filters enters the compressor side (2) of the turbocharger where it is compressed by the spinning turbine and picks up heat. The compressed air from the turbocharger then flows out the top of the turbocharger to the aftercooler. After the air is cooled by the aftercooler, the air flows to the cylinders and combines with the fuel for combustion.
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The compressed air that was heated at the turbochargers is routed through a finned Air to Air Aftercooler (ATAAC) core (arrow) mounted in front of the radiator. Outside air passes through the ATAAC core and the radiator to cool both the intake air and the engine c oolant. The cooled, compressed air exits the aftercoolers and is piped to the intake manifolds.
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Shown is the turbocharger outlet pressure sensor (1). The turbocharger outlet pressure sensor sends an input signal to the Engine ECM. The Engine ECM compares the value of the turbo outlet pressure sensor with the value of the atmospheric pressure sensor (2) and calculates boost pressure. The best way to check for a power problem is to compare the truck performance with the rimpull charts in the Caterpillar Performance Handbook or the individual specalogs for the 773F or 775F. The truck should be able to climb a grade in the same gear as specified in these two publications. If an engine power problem is suspected, check boost pressure at full load rpm. If boost pressure is correct at full load rpm, the engine is not the problem and other systems such as the torque converter should be checked. To check boost pressure at full load rpm, the truck must be operated in FIRST GEAR with the throttle at MAXIMUM and the retarder gradually engaged. Traveling up a grade is best as long as the engine rpm does not fall below the full load rpm specification during the test. Gradually engage the retarder until the full load rpm is displayed. When the full load rpm is displayed, record the boost pressure. If boost pressure is within the specifications at full load rpm, the engine is operating correctly. NOTE:
The monitoring system includes a transmission stall test that can be used to check boost at full load. Cat ET should be used to view the status while running the transmission stall test.
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Use Cat ET or the monitoring system display panel to view the engine rpm and boost pressure. Generally, Torque Converter (TC) stall speed (in gear, full throttle, zero ground speed) is used to determine if the engine power is low or a torque converter problem exists. For example, if the engine power is within specification and the stall speed is high, the torque converter may have a problem (low internal oil pressure, poor internal tolerances or damaged components). NOTE:
The 775F has a torque limiting function and engine speed is always limited to 1831 rpm during the stall test.
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The exhaust system (arrow) has been redesigned on the 773F/775F. The exhaust system exits on the right side of the machine and no longer runs through the frame.
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This schematic shows the flow through the air induction and exhaust system. The turbochargers are driven by the exhaust gas from the cylinders which enters the turbine side of the turbochargers. The exhaust gas flows through the turbochargers, the exhaust piping, and the mufflers. The clean air from the filters enters the compressor side of the turbochargers. The compressed air from the turbochargers flows to the ATAAC. After the air is cooled by the ATAAC, the air flows to the cylinders and combines with the fuel for combustion.
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6 5
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POWER TRAIN
The 773F/775F Off-highway Truck power train is electronically controlled. The Transmission/Chassis ECM controls the ECPC transmission shifting and the torque converter lockup clutch operation. The transmission has seven forward speeds and one reverse speed. Power flows from the engine to the rear wheels through the power train. The main power train components are: - Torque converter (1) - Drive shaft (2) - Transfer gears (3) - Transmission (4) - Differential (5) - Final drives (6) Other power train components visible in this illustration are the transmission charge filter (7) and the transmission oil cooler (8).
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These illustrations show the location of the main electronic components in the power train. The Transmission/Chassis ECM (1) is located behind the cab seat and is accessed by removing a panel at the rear of the cab. The transmission modulating valves (2) are located on top of the transmission planetary gears and are accessed by removing a cover plate. The torque converter lockup clutch solenoid valve (3) is located on the rear of the torque converter. NOTE:
The Transmission/Chassis ECM receives input signals from several components located on the machine to control transmission shifting and the torque converter lockup clutch operation. The electronic components will be covered later in the presentation.
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Power Train Hydraulic System
Shown is the transmission and torque converter hydraulic system for the 773F/775F. A twosection pump is located at the rear of the torque converter housing. The first section (attached to pump drive at rear of torque converter) takes oil from the bottom of the torque converter case and sends the oil to the transmission and torque converter oil filter and then to the torque converter lockup clutch valve and transmission control valves. Oil flows from the torque converter lockup clutch valve to the torque converter lockup clutch. Oil flows from the transmission control valves to the torque converter (TC inlet). Oil from the torque converter then flows to the outlet relief valve and the torque converter and transmission oil cooler. The second section scavenges oil from the transmission sump through a screen and sends oil to the torque converter case.
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This sectional view shows a torque converter in CONVERTER DRIVE. The lockup clutch (yellow piston and blue discs) is not engaged. During operation, the rotating housing and impeller (red) can rotate faster than the turbine (blue). The stator (green) remains stationary and multiplies the torque transfer between the impeller and the turbine. The output shaft rotates slower than the engine crankshaft, but with increased torque.
120
In DIRECT DRIVE, the lockup clutch is engaged by hydraulic pressure and locks the turbine to the impeller. The housing, impeller, turbine, and output shaft then rotate as a unit at engine rpm. The stator, which is mounted on a one-way clutch, is driven by the force of the oil in the housing. The one-way clutch permits the stator to turn freely in DIRECT DRIVE when torque multiplication is not required.
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Text Reference
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3
7 4
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122
5
The two-section power train pump (1) is located at the bottom rear of the torque converter. Oil flows from the charge pump to the torque converter lockup clutch (2). Oil from the charge pump also flows to the transmission to provide oil for the transmission modulating valves and then to the torque converter. Some of the oil will leak through the torque converter to the bottom of the housing to be scavenged. Most of the oil in the torque converter is used to provide a fluid coupling and flows through the torque converter outlet relief valve (3). The outlet relief valve maintains the minimum pressure inside the torque converter. The main function of the outlet relief valve is to keep the torque converter full of oil to prevent cavitation. The outlet relief pressure can be measured at the tap (4) on the outlet relief valve.
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From the outlet relief valve, oil flows to the torque converter and transmission oil cooler (5). The oil cooler is located on the right side of the engine. The torque converter lockup clutch valve directs oil to engage the torque converter lockup clutch. The torque converter lockup clutch pressure can be checked at the tap (6) on top of the lockup clutch valve. Excess oil that accumulates in the bottom of the transmission is scavenged by the first section of the pump through a screen behind the access cover (7) and returned to the torque converter sump. NOTE:
A torque converter outlet temperature sensor (not shown), located on the bottom of the outlet relief valve, provides an input signal to the Transmission/Chassis ECM. The ECM sends a signal to the monitoring system to inform the operator of the torque converter outlet temperature.
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The torque converter lockup clutch modulating valve contains a proportional solenoid that receives a signal from the Transmission/Chassis ECM to engage and release the torque converter lockup clutch. In this illustration, the lockup clutch modulating valve is shown with no current signal applied to the solenoid (TORQUE CONVERTER DRIVE or NEUTRAL). The Transmission/Chassis ECM controls the rate of oil flow through the lockup clutch modulating valve to the lockup clutch by changing the signal current strength to the solenoid. With no current signal applied to the solenoid, the transmission modulating valve is DE-ENERGIZED and oil flow to the clutch is blocked. Pump oil flows into the valve body around the valve spool and into a drilled passage in the center of the valve spool. The oil flows through the drilled passage and orifice to the left side of the valve spool to a drain orifice. Since there is no force acting on the pin assembly to hold the ball against the drain orifice, the oil flows through the spool and the drain orifice past the ball to the tank. The spring located on the right side of the spool in this view holds the valve spool to the left. The valve spool opens the passage between the clutch passage and the tank passage and blocks the passage between the clutch passage and the pump supply port. Oil flow to the clutch is blocked. Oil from the clutch drains to the tank preventing clutch engagement.
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In this illustration, the modulating valve is shown with a maximum current signal commanded to the solenoid. When the modulation cycle stops, the Transmission/Chassis ECM sends the maximum specified current signal to fully engage the lockup clutch (DIRECT DRIVE). The constant current signal pushes the pin firmly against the ball in the solenoid valve. The pin force against the ball blocks more oil from flowing through the drain orifice. This restriction causes an increase in pressure on the left side of the valve spool. The valve spool moves to the right to allow pump flow to fully engage the clutch. In a short period of time, maximum pressure is felt at both ends of the proportional solenoid valve spool. This pressure along with the spring force on the right end of the spool cause the valve spool to move to the left until the forces on the right end and the left end of the valve spool are balanced. The valve spool movement to the left (balanced) position reduces the flow of oil to the engaged clutch. The Transmission/Chassis ECM sends a constant maximum specified current signal to the solenoid to maintain the desired clutch pressure. NOTE:
The lockup clutch valve is calibrated with Cat ET.
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1 The torque converter and transmission charging filter (1) is located on the left frame rail behind the front tire. Oil from the charging pump flows through the torque converter filter and transmission to the torque converter lockup clutch valve.
2 3
4
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The filter has a bypass switch (2) which provides an input signal to the monitoring system, via the Transmission/Chassis ECM, to inform the operator if the filter is restricted. The filter housing includes a S•O•S tap (3) and a torque converter and transmission circuit pressure tap (4).
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Transmission Hydraulic System
The torque converter and transmission scavenge pump section pulls oil from the bottom of the transmission case through a magnetic screen and sends the oil to the torque converter sump. The magnetic screen should always be checked for debris if a problem with the transmission is suspected. The charging pump pulls oil from the torque converter sump. Charging oil flows from the pump through the transmission charging filter to the transmission main relief valve and seven modulating valves. The main relief valve regulates the torque converter inlet pressure and supply pressure inside the transmission hydraulic system. Oil unseats the check ball and forces the spool to the right if the transmission system pressure becomes greater than the spring force on the right of the spool. Excess oil will flow to the torque converter, lubrication circuit, and the lube relief valve. The lubrication circuit oil and oil from the lube relief valve flows to the transmission sump. The relief valve is adjustable by turning the adjusting screw on the right end of the valve.
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The clutch modulating valves control the engagement of the transmission clutches. The solenoids are controlled by a pulse width modulated (PWM) signal from the Transmission/Chassis ECM. Supply oil flows into the clutch modulating valves and through a passage in the center of the spool. Oil then flows to the tank if the solenoid is not energized. Oil flow is blocked by a ball and seat if the solenoid is energized. The spool will shift down and the clutch will begin to fill. The signal from the Transmission/Chassis ECM determines how long it takes to fill each clutch. The transmission lubrication relief valve limits the transmission lubrication oil pressure.
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The ECPC transmission hydraulic controls can be accessed by removing a cover plate (1) on top of the transmission. The transmission input speed sensor (2) is located on top of the transfer gear housing. The transmission input speed sensor sends an input to the Transmission/Chassis ECM which checks the speed of the drive shaft to the speed of the engine. The transmission has pressure taps located on the outside of the transmission which aids in preventing contamination from entering the transmission as well as saving time when checking the pressures on the 773F/775F transmission. The transmission lubrication pressure tap (3) and the transmission hydraulic system pressure tap (4) are located toward the rear of the transmission. Oil pressure for the seven clutches can be checked at the remaining seven taps (5) on the transmission. Lube pressure can also be checked at the tap (6) on the left side of the transmission. The torque converter and transmission breather (7) is located at the rear of the transmission.
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The transmission modulating valves control the oil to corresponding transmission clutches. The solenoid valves are: - Clutch No. 1 Solenoid valve (1) - Clutch No. 2 Solenoid valve (2) - Clutch No. 3 Solenoid valve (3) - Clutch No. 4 Solenoid valve (4) - Clutch No. 5 Solenoid valve (5) - Clutch No. 6 Solenoid valve (6) - Clutch No. 7 Solenoid valve (7) The main relief valve (8) controls the transmission hydraulic pressure, and the lubrication relief valve (not visible) controls the lubrication pressure. The lubrication relief valve is located below the main relief valve. Also located on the transmission hydraulic control valve is the transmission hydraulic oil temperature sensor (9). The temperature sensor sends a signal to the Transmission/Chassis ECM indicating transmission oil temperature.
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The table in this illustration lists the solenoids that are energized and clutches that are engaged for each transmission speed. This table can be useful for transmission diagnosis.
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In this illustration, the transmission modulating valve is shown with no current signal applied to the solenoid. The Transmission/Chassis ECM controls the rate of oil flow through the transmission modulating valves to the clutches by changing the signal current strength to the solenoid. With no current signal applied to the solenoid, the transmission modulating valve is DE-ENERGIZED and oil flow to the clutch is blocked. Pump oil flows into the valve body around the valve spool and into a drilled passage in the center of the valve spool. The oil flows through the drilled passage and orifice to the left side of the valve spool to a drain orifice. Since there is no force acting on the pin assembly to hold the ball against the drain orifice, the oil flows through the spool and the drain orifice past the ball to the tank. The spring located on the right side of the spool in this view holds the valve spool to the left. The valve spool opens the passage between the clutch passage and the tank passage and blocks the passage between the clutch passage and the pump supply port. Oil flow to the clutch is blocked. Oil from the clutch drains to the tank preventing clutch engagement.
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In this illustration, the modulating valve is shown with a signal to the solenoid that is below the maximum current. Clutch engagement begins when the Transmission/Chassis ECM sends an initial current signal to ENERGIZE the solenoid. The amount of commanded current signal is proportional to the desired pressure that is applied to the clutch during each stage of the engagement and disengagement cycle. The start of clutch engagement begins when the current signal to the solenoid creates a magnetic field around the pin. The magnetic force moves the pin against the ball in proportion to the strength of the current signal from the Transmission/Chassis ECM. The position of the ball against the orifice begins to block the drain passage of the oil flow from the left side of the valve spool to the tank. This partial restriction causes the pressure at the left end of the valve spool to increase. The oil pressure moves the valve spool to the right against the spring. As the pressure on the right side of the valve spool overrides the force of the spring, the valve spool shifts to the right. The valve spool movement starts to open a passage on the right end of the valve spool for pump supply oil to fill the clutch. Oil also begins to fill the spring chamber on the right end of the spool.
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In the initial clutch filling stage, the Transmission/Chassis ECM commands a high current pulse to quickly move the valve spool to start filling the clutch. During this short period of time, the clutch piston moves to remove the clearances between the clutch discs and plates to minimize the amount of time required to fill the clutch. The ECM then reduces the current signal which reduces the pressure setting of the proportional solenoid valve. The change in current signal reduces the flow of oil to the clutch. The point where the clutch plates and discs start to touch is called TOUCH-UP. Once TOUCH-UP is obtained, the Transmission/Chassis ECM begins a controlled increase of the current signal to start the MODULATION cycle. The increase in the current signal causes the ball and pin to further restrict oil through the drain orifice to tank causing a controlled movement of the spool to the right. The spool movement allows the pressure in the clutch to increase. During the MODULATION cycle, the valve spool working with the variable commanded current signal from the Transmission/Chassis ECM acts as a variable pressure reducing valve. The sequence of partial engagement is called desired slippage. The desired slippage is controlled by the application program stored in the Transmission/Chassis ECM.
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In this illustration, the modulating valve is shown with a maximum current signal commanded to the solenoid. When the modulation cycle stops, the Transmission/Chassis ECM sends the maximum specified current signal to fully engage the clutch. The constant current signal pushes the pin firmly against the ball in the solenoid valve. The pin force against the ball blocks more oil from flowing through the drain orifice. This restriction causes an increase in pressure on the left side of the valve spool. The valve spool moves to the right to allow pump flow to fully engage the clutch. In a short period of time, maximum pressure is felt at both ends of the proportional solenoid valve spool. This pressure along with the spring force on the right end of the spool cause the valve spool to move to the left until the forces on the right end and the left end of the valve spool are balanced. The valve spool movement to the left (balanced) position reduces the flow of oil to the engaged clutch. The Transmission/Chassis ECM sends a constant maximum specified current signal to the solenoid to maintain the desired clutch pressure.
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The different maximum specified pressures for each clutch is caused by different maximum current signals being sent by the Transmission/Chassis ECM to each individual modulating valve. The different maximum signal causes a difference in the force pushing the pin against the ball to block leakage through the drain orifice in each solenoid valve. The different rate of leakage through the spool drain orifice provides different balance positions for the proportional solenoid valve spool. Changing the valve spool position changes the flow of oil to the clutch and the resulting maximum clutch pressure. The operation of the proportional solenoid to control the engaging and releasing of clutches is not a simple on and off cycle. The Transmission/Chassis ECM varies the strength of the current signal through a programmed cycle to control movement of the valve spool. The clutch pressures can be changed using Caterpillar Electronic Technician (ET) during the calibration procedure.
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The transmission hydraulic control relief valve is used to regulate the pressure to the torque converter and the main components in the transmission. Oil enters the relief valve at the supply port. The pressure of the oil unseats the ball and moves the spool toward the right. Oil flows past the spool and to the torque converter to regulate transmission oil pressure. The adjustment screw alters the preload on the spring to adjust the relief pressure.
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135
1 5
2
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4
Rear Axle
Check the differential oil level by removing the magnetic inspection plug (1). The oil should be level with the bottom of the fill plug opening. The magnetic inspection plug should be removed at regular intervals and checked for metal particles. The plug (2) at the bottom of the differential housing is used to drain the oil. Inspect the condition of the rear axle breather (3), located behind the rear suspension cylinder at regular intervals. The breather prevents pressure from building up in the axle housing. Excessive pressure in the axle housing can cause brake cooling oil to leak through the Duo-Cone seals in the wheel brake assemblies. The parking brake oil pressure can be checked at the pressure taps (4) on top of the axle.
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A differential carrier thrust pin is located behind the small cover (5). The thrust pin prevents movement of the differential carrier during high thrust load conditions. The back-up alarm (6) is located on top of the rear frame. When the machine is in reverse, the Transmission/Chassis ECM sends a signal to sound the back-up alarm.
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Shown is the differential removed from the rear axle housing. The differential is located in the rear axle housing behind the transmission. Power flows from the transmission to the differential. The differential divides the power to the right and left axle shafts. Torque is transmitted equally from the differential through the two axle shafts to the final drives. The differential adjusts the speed of the axle shafts for vehicle cornering, therefore, the power delivered to the axle shafts is unequal during cornering. The differential thrust pin contacts the differential carrier at the location shown (arrow). When high thrust loads are transmitted from the differential pinion to the differential ring gear, the carrier tries to move away from the pinion. The thrust pin prevents movement of the differential carrier during high thrust load conditions.
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Transmission/Chassis Electronic Control System
Shown in this illustration are the transmission/chassis electronic control system inputs and outputs for the 773F/775F Trucks. The main purpose of the Transmission/Chassis ECM is to determine the desired transmission gear and to energize the appropriate solenoids to shift the transmission up or down as required based on information from both the operator and machine. The Transmission/Chassis ECM also controls all the hoist functions, the steering disable function, and other functions as described in this presentation. The Transmission/Chassis ECM receives information from various input components such as the shift lever switch and the transmission output speed sensors. Based on the input information, the Transmission/Chassis ECM determines whether the transmission should upshift, downshift, engage the lockup clutch, or limit the transmission gear. These actions are accomplished by sending signals to various output components.
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Power train output components include the transmission modulating valve solenoids and the lockup clutch solenoid. Several other Transmission/Chassis ECM output components are covered throughout the presentation. The Engine ECM, the monitoring system, the Transmission/Chassis ECM, and the Brake ECM all communicate with each other through the CAT Data Link. Communication between the electronic control modules allows the sensors of each system to be shared. Many additional benefits are provided, such as Controlled Throttle Shifting (CTS). CTS occurs when the Transmission/Chassis ECM tells the Engine ECM to reduce or increase engine fuel during a shift to lower stress to the power train. The Electronic Technician (ET) Service Tool can be used to perform several diagnostic and programming functions. NOTE:
Some of the Transmission/Chassis ECM input and output components are shown during the discussion of other systems.
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The Transmission/Chassis ECM (arrow) is located in the compartment at the rear of the cab. The Transmission/Chassis ECM performs the transmission control functions, plus some other machine functions (hoist and secondary steering control). Because of the functionality of the control, it is referred to as the Transmission/Chassis ECM. The Transmission/Chassis ECM is an A4M1 module with two 70-pin connectors. The Transmission/Chassis ECM communicates with the Engine ECM, the Brake ECM, and the monitoring system over the CAT Data Link and can communicate with some attachments over the CAN Datalink.
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6 2
8
7
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5 3
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At the base of the shift lever (1) is a position sensor (2) which provides input signals to the Transmission/Chassis ECM when the operator moves the lever. The shift lever position sensor is a Hall-effect position sensor. The shift lever is connected to a device which contains two magnets. One magnet (3) is visible in the bottom left view. As the lever is moved, the magnets pass over the Hall Cell (4) and the change in the magnetic field produces a signal. The internal electronics (5) of the sensor process the signal and send a PWM signal to the ECM. The lever position sensor receives 24 VDC from the machine electrical system. The sensor contains a fourth pin that is used for calibration on some machine applications. The following measurements would be typical for the position sensor with the sensor connected to the Transmission/Chassis ECM and the key switch turned ON: • Pin 1 to Pin 2 -- Supply Voltage • Pin 3 to Pin 2 -- .7 - 6.9 DCV on DC volts scale • Pin 3 to Pin 2 -- 4.5 - 5.5 KHz on the KHz scale • Pin 3 to Pin 2 -- 5% - 95% duty cycle on the % scale
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Also shown in the top right illustration is the drive gear UP switch (6) and the drive gear DOWN switch (7). The drive gear switches are toggle switches that send a signal to the Transmission/Chassis ECM. When the drive gear UP switch is pressed, the high gear limit can be increased up to seventh gear. When the drive gear DOWN switch is pressed, the high gear limit can be decreased down to third gear. The transmission shift lever lock button (8) unlocks the transmission shift lever when pressed.
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The transmission output speed sensors (arrows) are located on the transfer gear housing on the input end of the transmission behind a cover (not shown). Although the sensors are physically located near the input end of the transmission, the sensors are measuring the speed of the transmission output shaft. The sensors are two wire passive sensors. The passive speed sensor uses the passing teeth of the output shaft to provide a frequency signal. The signal from the sensor is used for automatic shifting of the transmission. The signal is also used to drive the speedometer and as an input to other electronic controls. The Transmission/Chassis ECM also performs a check between the two measured transmission output speeds and the transmission input speed to ensure that the ECM calculates an accurate transmission speed. This check also uses the speeds to determine the direction of motion of the machine.
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The engine speed sensor (arrow) is located at the rear of the engine on the left side of the gear housing. The engine speed sensor sends a frequency signal to the Transmission/Chassis ECM indicating engine speed. The Transmission/Chassis ECM uses the engine speed signal input to determine actual engine speed. The actual engine speed is one of the parameters used to determine the proper transmission shift points.
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1
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The body up switch (1) is located on the frame near the body pivot pin. This magnetic switch is normally open. When the body is raised, a magnet (2) mounted on the body passes the switch and causes the switch to close. The resulting ground signal is sent to the Transmission/Chassis ECM. This signal is used to limit the top gear into which the transmission will shift when the body is up. The body up top gear value is programmable from FIRST to THIRD utilizing the Cat ET Service Tool. The ECM comes from the factory with this value set to FIRST gear. When driving away from a dump site, the transmission will not shift past FIRST gear until the body is down. If the transmission is already above the set limit gear when the body is raised, no limiting action will take place. The body up switch signal is also used to control the SNUB position of the hoist control valve. As the body is lowered and the magnet passes the body up switch, the Transmission/Chassis ECM signals the hoist lower solenoid to move the hoist valve spool to the SNUB position. In the SNUB position, the body float speed is reduced to prevent the body from making hard contact with the frame. The body up switch input provides the following functions: - Body up gear limiting - Hoist snubbing - Illuminates the backup lights - Lights the body up dash lamp - Signals a new load count (after 10 seconds in the RAISE position)
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A diagnostic code occurs if the Transmission/Chassis ECM does not receive a closed (ground) signal from the switch within four hours of operation time or an open signal from the switch within one hour of operation time. The body up switch must be adjusted properly for all of the functions to operate correctly. The body position switch can be raised or lowered slightly in the bracket notches to start the SNUB feature sooner or later. NOTE:
The snub feature can also be adjusted in the Cat ET hoist configuration screen by selecting the "Hoist lower valve adjustment status".
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Besides controlling the Transmission Shifting and Torque Converter Lockup, the Transmission/Chassis ECM also controls other functions as shown above, such as Control Throttle Shifting (CTS), Directional Shift Management, and Top Gear Limit. There are several programmable parameters available with the Transmission/Chassis ECM. NOTE:
Refer to the Transmission/Chassis Electronic Control System Operation, Troubleshooting, Testing, and Adjusting manual (RENR8342) for more information on the additional Transmission/Chassis ECM functions and programmable parameters.
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STEERING SYSTEM
The steering system on the 773F/775F is similar to the D and E Series trucks except a steering disable solenoid valve has been added and some of the component locations have changed. When energized, the steering disable solenoid valve stops the oil flow coming from the steering pump. This prevents the front wheels from turning to allow servicing to be conducted safely in the front wheel area. The steering system uses a load sensing, pressure compensated pump. Minimal horsepower is used by the steering system when the truck is traveling in a straight path. Steering hydraulic horsepower requirements depend on the amount of steering pressure and flow required by the steering cylinders. This illustration shows the following main steering components: - Steering pump (1)
- Steering cylinders (5)
- Steering disable valve (2)
- Steering tank (6)
- Steering valve (3)
- Secondary steering pump (7)
- HMU (4)
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1
3
2 147
The steering system tank is located on the right platform. Check the steering system oil level at the sight gauge (1). The steering system oil filter (2) is located next to the steering tank below an access panel. The steering system uses a pressure compensated piston-type pump. Case drain oil from the steering pump returns to the hydraulic tank through a case drain filter (3) also located below the access panel. Before removing the cap (4) to add oil to the steering system, depress the pressure release button (5) on the breather to release any remaining pressure from the tank.
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The steering system filter base and the case drain filter base have bypass valves that allow the steering oil to bypass the filters if they are plugged.
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2
149
2
1
The 773F/775F trucks are equipped with a load sensing, pressure compensated, piston-type pump. The steering pump operates only when the engine is running and provides the necessary flow of oil for steering system operation. The steering pump contains a load sensing controller with two valves. The high pressure cutoff valve (1) functions as the primary steering system relief valve. The flow compensator valve (2) is used to adjust the low pressure standby setting. When the truck is traveling in a straight path, virtually no flow or pressure is sent to the steering cylinders, and the pump destrokes to low pressure standby.
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When the truck is traveling in a straight path, the steering cylinders require virtually no flow or pressure. The HMU provides a very low pressure load sensing signal to the flow compensator in the load sensing controller. Pump oil (at low pressure standby) flows to the swashplate piston and past the lower end of the displaced flow compensator spool to the actuator piston. The actuator piston has a larger surface area than the swashplate piston. The oil pressure at the actuator piston overcomes the spring force and the oil pressure in the swashplate piston and moves the swashplate to destroke the pump. The pump is then at minimum flow, low pressure standby. Pump output pressure is equal to the setting of the flow compensator plus the pressure required to compensate for system leakage.
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During a turn, when steering pressure and flow are required, pressure increases in the HMU load sensing signal line. The pressure in the signal line is equal to the pressure in the steering cylinders. The pump load sensing controller is spring biased to vent the actuator piston pressure to drain. Venting pressure from the load sensing controller and the actuator piston positions the spring biased swashplate to maximum displacement (maximum flow). As pressure increases in the HMU load sensing signal line, pump supply pressure is sensed on both ends of the flow compensator. When pressure is present on both ends of the flow compensator, the swashplate is kept at maximum angle by the force of the spring in the pump housing and pump discharge pressure on the swashplate piston. The pistons reciprocate in and out of the barrel and maximum flow is provided through the outlet port. Since the pump is driven by the engine, engine rpm also affects pump output.
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1
2
1
153
The steering disable valve (1) is located behind the shock on the right frame rail. When the steering disable solenoid valve (2) is energized, oil flow from the steering pump to the steering valve is blocked by the steering disable valve, which allows servicing behind the front wheels with the machine running. When the machine lockout switch, located under a panel on the left stairway, is toggled, a signal is sent to the Transmission/Chassis ECM. The Transmission/Chassis ECM energizes the steering disable solenoid allowing service to be performed behind the front wheels safely. Also located on the steering disable valve is a pressure tap for checking the load sensing signal to the pump, and an S•O•S tap. The taps (not visible) are located on the front of the steering disable valve.
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Steering oil flows from the pump through the steering disable valve to the steering valve (1) located on the frame behind the right front suspension cylinder. The primary steering pressure switch (2) monitors the output of the steering pump. The steering pressure switch provides input signals to the Transmission/Chassis ECM which sends a signal to the monitoring system to inform the operator of the steering system condition. A steering system warning is displayed if the pressure is too low. The steering pressure switch cannot tolerate high steering system pressures. A pressure reducing valve (3) reduces the steering system pressure to the steering pressure switch. Two relief valves are located on the left side of the steering valve. The top relief valve (4) is a back-up relief valve for the secondary steering system. The secondary steering back-up relief valve protects the secondary steering system if the relief valve on the secondary steering pump malfunctions. The lower relief valve (5) is a back-up relief valve for the primary steering system. The primary steering back-up relief valve protects the primary steering system if the high pressure cut-off valve on the steering pump malfunctions. Primary steering pressure is first controlled by the high pressure cutoff valve located on the steering pump.
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Check valves are used to separate the primary and secondary steering systems. The secondary check valve (6) is behind the left plug, and the primary check valve (7) is behind the right plug. Steering system pressures can be measured at the steering system pressure tap (8).
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This illustration shows the location of the HMU (arrow) for the 773F/775F. Serviceability has improved for the HMU on the 773F/775F due to the redesigned walkways. The HMU is connected to the steering wheel and controlled by the operator. The HMU meters the amount of oil sent to the steering cylinders by the speed at which the steering wheel is turned. The faster the HMU is turned, the higher the flow sent to the steering cylinders, and the faster the wheels will change direction. The steering system is referred to as "Q-amp" which means flow amplification. During a sudden steering change (steering wheel speed greater than 10 rpm), additional steering pump oil flow will bypass the gerotor pump in the HMU and flow directly to the steering cylinders. Steering oil flow to the cylinders is equal to the gerotor pump oil flow plus the bypass oil flow from the steering pump. The steering oil flow is amplified up to 1.6 to 1. The purpose of the flow amplification is to provide quick steering response when sudden steering changes are needed. Two crossover relief valves are installed in the top of the HMU. The crossover relief valves are installed in series with the left and right turn ports. If an outside force is applied to the front wheels while the steering wheel is stationary, the crossover relief valves provide circuit protection for the steering lines between the steering cylinders and the HMU. The crossover relief valves allow oil to transfer from one end of the steering cylinders to the opposite end of the cylinders.
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To test the right crossover relief valve, install two tees with pressure taps in the right turn steering hose at the steering cylinders. Steer the truck completely to the right against the stops, and shut off the engine. An external pump supply must be connected to one of the pressure taps on the right turn hose. Connect a pressure gauge to the other pressure tap on the right turn hose. Pressurize the steering system, and the reading on the gauge will be the setting of the right crossover relief valve. To test the left crossover relief valve, install two tees with pressure taps in the left turn steering hose at the steering cylinders. Steer the truck completely to the left against the stops, and shut off the engine. An external pump supply must be connected to one of the pressure taps on the left turn hose. Connect a pressure gauge to the other pressure tap on the left turn hose. Pressurize the steering system, and the reading on the gauge will be the setting of the left crossover relief valve.
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The electric secondary steering pump (1) and motor (2) on the 773F/775F are the same as the 773D/775D, however the location has changed. The pump and motor are now located on the front of the front frame crossmember. The pump and motor assembly also includes the brake release pump section (3) and the prelubrication (QuickEvac) pump section (4). The secondary pressure switch (not visible) is also mounted next to the secondary steering pump. The pressure switch detects if the wheels are being turned via the steering wheel when secondary steering is activated. When the wheel is turned in a secondary steering condition, the pressure switch will signal the Transmission/Chassis ECM.
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If the primary steering pressure switch signals the Transmission/Chassis ECM that the steering system pressure is low, the ECM will energize the secondary steering relay located behind the cab. The secondary steering relay will then energize a second larger relay located on the left frame, which will then energize the secondary steering motor. The primary relief valve for the secondary steering is accessible through the small allen head plug (5). To check the setting of the secondary steering primary relief valve, do not start the truck. Turn ON the key start switch and depress the secondary steering switch in the cab. Turn the steering wheel hard to the left or right while the secondary steering pump is running. Secondary steering system pressures can be measured at the steering system pressure tap.
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Shown is a schematic of the steering hydraulic system in the HOLD position. The primary steering pump pulls oil from the steering tank. All piston-type pumps produce a small amount of leakage to the case drain circuit for lubrication and cooling. The case drain oil flows to the steering tank through a case drain filter. Steering oil flows from the pump to the steering disable valve. When the steering disable valve is energized, oil is allowed to flow to the steering valve. In the steering valve, a steering pressure switch monitors the output of the steering pump. The steering pressure switch cannot tolerate high steering system pressures. A pressure reducing valve lowers the steering system pressure to the steering pressure switch. If the steering pressure switch signals the Transmission/Chassis ECM that the steering system pressure is low, the ECM will then energize the secondary steering motor. Secondary steering supply oil will flow to the steering valve.
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Text Reference
Two relief valves are installed in the steering valve. The secondary steering back-up relief valve protects the secondary steering system if the relief valve on the secondary steering pump malfunctions. The primary steering back-up relief valve protects the primary steering system if the high pressure cut-off valve on the steering pump malfunctions. Two check valves are located on the steering valve. The check valves are used to separate the primary and secondary steering systems. Steering supply oil flows to the HMU from the steering valve. Return oil from the HMU flows through the steering valve and the steering filter to the steering tank. The HMU meters the amount of oil sent to the steering cylinders by the speed at which the steering wheel is turned. The faster the HMU is turned, the higher the flow sent to the steering cylinders, and the faster the wheels will change direction. Two crossover relief valves are installed in the top of the HMU. The crossover relief valves are installed in series with the left and right turn ports. If an outside force is applied to the front wheels while the steering wheel is stationary, the crossover relief valves provide circuit protection for the steering lines between the steering cylinders and the HMU. The crossover relief valves allow oil to transfer from one end of the steering cylinders to the opposite end of the cylinders. When the Transmission/Chassis ECM energizes the secondary steering motor, load sensing signal oil will flow from the secondary steering load sensing valve through the load sensing resolver to the HMU. The load sensing valve uses the load sensing signal pressure to control the amount of flow from the secondary steering pump to the steering valve. The 773F/775F Trucks use a dynamic load sensing steering system the same as the late model "D Series" Trucks. In a dynamic system, there is load sensing pressure and flow between the HMU and the steering pumps. A load sensing pilot signal resolver valve is located in the steering disable valve. The resolver valve allows load sensing signal oil to flow between the HMU and the primary steering pump or the secondary steering pump. In the NO STEER position, oil flows to the HMU. In a LEFT or RIGHT STEER position, oil also flows from the HMU to the resolver valve. Normally, the secondary steering pump is OFF and the resolver is closed from the HMU to the secondary steering pump. The flow from the primary steering pump holds the resolver open and load sensing pilot signal pressure is present between the HMU and the piston pump flow compensator. The load sensing signal flow from the primary steering pump is also used for "thermal bleed" through the HMU. The "thermal bleed" is used to keep the HMU temperature the same as the rest of the steering system. Keeping the HMU the same temperature prevents sticking.
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Text Reference
4 3
2
1 3
159
HOIST SYSTEM
The hoist system on the 773F/775F Update trucks is electronically controlled by the Transmission/Chassis ECM. The hoist control system operates similar to the 773D/775D trucks. The main components in the hoist system are: - Hoist control lever and position sensor (in cab) - Hoist pump (1) - Hoist control valve (2) - Hoist cylinders (3) - Hydraulic oil tank (4)
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160
The operator controls the hoist lever (arrow). The four positions of the hoist lever are RAISE, HOLD, FLOAT, and LOWER. The hoist valve has a fifth position referred to as the SNUB position. The operator is unaware of the SNUB position because a corresponding lever position is not provided. When the body is being lowered, just before the body contacts the frame, the Transmission/Chassis ECM signals the hoist lower solenoid to move the hoist valve spool to the SNUB position. In the SNUB position, the body float speed is reduced to prevent the body from making hard contact with the frame. The hoist system can be enabled or disabled using ET. All trucks shipped from the factory without bodies installed are set at the DISABLED mode. The DISABLED mode is a test mode only and will prevent the hoist cylinders from accidentally being activated. After the body is installed, change the hoist system to ENABLED for the hoist system to function properly. The truck should normally be operated with the hoist lever in the FLOAT position. Traveling with the hoist in the FLOAT position will make sure the weight of the body is on the frame and the body pads and not on the hoist cylinders. The hoist control valve will actually be in the SNUB position. If the transmission is in REVERSE when the body is being raised, the hoist lever sensor is used to shift the transmission to NEUTRAL. The transmission will remain in NEUTRAL until the hoist lever is moved into the HOLD or FLOAT position and the shift lever has been cycled into and out of NEUTRAL. NOTE:
If the truck is started with the body raised and the hoist lever in FLOAT, the lever must be moved into HOLD and then FLOAT before the body will lower.
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Text Reference
1
3
2
161
The hoist lever (1) controls a position sensor (2). The PWM sensor sends duty cycle input signals to the Transmission/Chassis ECM. The hoist lever position sensor is a Hall-effect position sensor and operates the same as the transmission shift lever sensor (3) previously described. Depending on the position of the sensor and the corresponding duty cycle, one of the two solenoids located on the hoist valve is energized. The four positions of the hoist lever are RAISE, HOLD, FLOAT, and LOWER, but since the sensor provides a duty cycle signal that changes for all positions of the hoist lever, the operator can modulate the speed of the hoist cylinders. The hoist lever sensor performs the following three functions: - Raises and lowers the body - Neutralizes the transmission in REVERSE - Starts a new TPMS cycle
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Text Reference
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2
162
Shown is the hoist and brake hydraulic tank. The oil level is checked by opening the small door (1) and looking at the sight gauge. The oil level should first be checked with cold oil and the engine stopped. The level should again be checked with warm oil and the engine running. The lower sight gauge (2) can be used to fill the tank when the hoist cylinders are in the RAISED position. When the hoist cylinders are lowered, the hydraulic oil level will increase. After the hoist cylinders are lowered, check the hydraulic tank oil level with the upper sight gauge as explained above. The hoist and brake tank breather is accessed by removing a cover (3) on top of the tank. Check the tank breather for restriction and clean or replace as necessary.
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Text Reference
2
4 3
5 6
1
8
7
163
Shown is the rear of the hoist and brake hydraulic tank. The hoist pump pulls oil from the tank through the suction screen (1) located in the rear of the tank. Brake cooling oil returns to the hydraulic tank through the upper port (2). Oil returns from the hoist valve through the port (3). Other ports located on the hydraulic tank are: - Makeup tank return port (4) - Towing diverter valve return (5) - Towing pump suction (6) - Brake charging pump suction (7) - Parking brake return (8)
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164
1
2
1
165
The hoist pump (1) is a gear-type pump that is attached to the drive gear at the rear of the engine. Mounted to the hoist pump is the brake charging pump. Oil flows from the hoist pump to the hoist control valve. The hoist system relief pressures are different in the RAISE and LOWER positions. The body up switch must be in the RAISE position before the LOWER relief valve setting can be tested. Move a magnet past the body up switch until the body up alert indicator on the dash turns ON. If the body up switch is in the LOWER position, the Transmission/Chassis ECM will hold the hoist valve in the SNUB position and the LOWER relief valve will not open.
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Text Reference
In the HOLD, FLOAT, and SNUB positions, the gauge will show the brake cooling system pressure, which is a result of the restriction in the coolers, brakes, and hoses (normally much lower than the actual oil cooler relief valve setting). The maximum pressure is limited by the oil cooler relief valve. Hoist pump pressure can be checked at the pressure tap (2) on the pump.
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Text Reference
2
166
2 1
3
167
4
The hoist control valve (1) is located behind the engine on the right side of the frame. The hoist valve is the same as the hoist control valve on the D and E Series Trucks. The hoist valve uses parking brake oil pressure that has been reduced by the pressure reducing valve as the pilot oil to shift the directional spool inside the hoist valve. Oil enters the hydraulic actuators (2) on both ends of the hoist valve. Pilot pressure can be adjusted at the pressure reducing valve (3) located next to the diverter valve (4) on the left frame rail in front of the left front strut.
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Text Reference
7 6 1
2
3
4
5
168
Pilot oil pressure is always present at both ends of the directional spool. Two solenoid valves are used to drain the pilot oil from the ends of the directional spool, which then allows the spool to move. The solenoid on the right is the RAISE solenoid valve (1), and the solenoid on the left is the LOWER solenoid valve (2). The left pressure tap (3) is used to check the pilot pressure of the hoist lower solenoid. The right pressure tap (4) is used to check the pilot pressure of the raise solenoid. When the Transmission/Chassis ECM receives an input signal from the hoist lever sensor, the ECM sends an output signal current between 0 and 1.9 amps to one of the solenoids. The amount of current sent to the solenoid determines how much pilot oil is drained from the end of the directional spool and, therefore, how far the directional spool travels toward the solenoid. An oil cooler relief valve is located in the hoist control valve behind the large plug (5). The relief valve limits the brake oil cooling pressure when the hoist valve is in the HOLD, FLOAT, or SNUB position. The hoist system relief pressures are controlled by the two relief valves located on top of the hoist valve. The RAISE relief valve (6) limits the pressure in the hoist system during RAISE. The LOWER relief valve (7) limits the pressure in the hoist system during LOWER. NOTE:
The hoist valve LOWER position (snub adjustment) is an adjustable parameter in the Transmission/Chassis ECM using Cat ET. The slight adjustment provides a means to compensate for valve differences. This is the snub adjustment.
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Text Reference
2
1
169
The hoist cylinder lower circuit pressure tap (1) and raise circuit pressure tap (2) are located on the cross-tube between the lower hoist cylinder mounts. The relief valve pressure setting is tested with the engine at HIGH IDLE and the hoist valve in the RAISE or LOWER position. The body up switch at the frame near the body pivot pin must be in the RAISE position before the LOWER relief valve setting can be tested. Move a magnet past the body up switch until the body up alert indicator on the dash turns ON. If the body up switch is in the LOWER position, the Transmission/Chassis ECM will hold the hoist valve in the SNUB position and the LOWER relief valve will not open. An orifice plate is installed between the upper hose and the rod end port on both hoist cylinders. The orifice plate restricts the flow of oil from the rod end of the hoist cylinders. The orifice plate also prevents cavitation of the cylinders when the body raises faster than the pump can supply oil to the cylinders (caused by a sudden shift of the load). NOTE:
If the snub feature is not adjusted correctly, residual pressure will exist in the head side of the cylinders and the body will not rest on the frame. The raise circuit pressure tap should be used to ensure there is no residual pressure in the head side of the cylinders.
Otherwise, when checking the raise (high) circuit pressure, the pressure tap on the hoist pump is easier to access.
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Text Reference
170
This illustration shows a sectional view of the hoist control valve in the HOLD position. Pilot oil pressure is present at both ends of the directional spool. The spool is held in the centered position by the centering springs and the pilot oil. Passages in the directional spool vent the dual stage relief valve signal stem to the tank. All the hoist pump oil flows through the brake oil coolers to the rear brakes. The position of the directional spool blocks the oil in the head end and rod end of the hoist cylinders. A gauge connected to a pressure tap at the pump while the hoist valve is in the HOLD position will show the brake cooling system pressure, which is a result of the restriction in the coolers, brakes, and hoses. The maximum pressure in the circuit should correspond to the setting of the brake oil cooler relief valve.
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171
In the RAISE position, the raise solenoid is ENERGIZED and drains pilot oil from the upper end of the directional spool. The directional spool moves up. Pump oil flows past the load check valve and the directional spool to the head end of the hoist cylinders. When the directional spool is initially shifted, the load check valve remains closed until the supply pressure is higher than the pressure in the hoist cylinders. The load check valve prevents the body from dropping before the RAISE pressure increases. The directional spool also sends hoist cylinder raise pressure to the dual stage relief valve signal stem. The dual stage relief valve signal stem moves down and blocks the supply pressure from opening the low pressure relief valve. Oil flowing from the rod end of the hoist cylinders flows freely through the brake oil cooler to the brakes. If the pressure in the head end of the hoist cylinders exceeds the relief valve settings, the high pressure relief valve will open. When the high pressure relief valve opens, the dump valve moves to the left and pump oil flows to the tank.
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Text Reference
The high pressure hoist relief valve setting is checked at the hoist pump pressure tap or the head end pressure tap. Check the relief pressure with the hoist lever in the RAISE position and the engine at HIGH IDLE.
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Text Reference
172
In the LOWER (power down) position, the LOWER solenoid is energized and drains pilot oil from the lower end of the directional spool. The directional spool moves down. Supply oil from the pump flows past the load check valve and the directional spool to the rod end of the hoist cylinders. Oil in the head end of the hoist cylinders flows to the tank through holes in the directional spool. The supply oil in the rod end of the cylinders and the weight of the body move the cylinders to their retracted positions. Just before the body contacts the frame, the body up switch sends a signal to the Transmission/Chassis ECM to move the directional spool to the SNUB position. In the SNUB position, the directional spool moves slightly to restrict the flow of head end oil through only some of the holes in the spool which allows the body to lower gradually. The directional spool also vents the passage to the dual stage relief valve signal stem. The dual stage relief valve signal stem allows supply pressure to be limited by the low pressure relief valve. If the pressure in the rod end of the hoist cylinders is too high, the low pressure relief valve will open. When the low pressure relief valve opens, the dump valve moves to the left and pump oil flows to the tank.
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Text Reference
The low pressure hoist relief valve setting is checked at the rod end pressure tap. Check the relief pressures with the hoist lever in the LOWER position and the engine at HIGH IDLE. The body up switch must be in the RAISE position before the LOWER relief valve setting can be tested. Move a magnet past the body up switch until the body up alert indicator on the dash turns ON. If the body up switch is in the LOWER position, the Transmission/Chassis ECM will hold the hoist valve in the SNUB position and the LOWER relief valve will not open.
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Text Reference
173
In the FLOAT position, the LOWER solenoid is partially energized and drains some of the pilot oil at the lower end of the directional spool to the tank. The directional spool moves down. Because the pilot oil is only partially drained, the directional spool does not move down as far as during LOWER (power down). Pump supply oil flows past the load check valve and the directional spool to the rod end of the hoist cylinders. Oil in the head end of the hoist cylinders flows to the tank. The position of the directional spool permits the pressure of the oil flowing to the brake oil cooler to be felt at the rod end of the hoist cylinders. The truck should normally be operated with the hoist lever in the FLOAT position. Traveling with the hoist in the FLOAT position will make sure the weight of the body is on the frame and body pads and not on the hoist cylinders. The hoist valve will actually be in the SNUB position.
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Text Reference
174
In the SNUB position as the body is lowered, just before the body contacts the frame, the body up switch sends a signal to the Transmission/Chassis ECM to move the directional spool to the SNUB position. In the SNUB position, the directional spool moves slightly to a position between HOLD and FLOAT. The SNUB position restricts the flow of oil and lowers the body gradually. The operator does not control the SNUB position. When the hoist lever is in the LOWER or FLOAT position and the body up switch is in the DOWN position, the hoist control valve is in the SNUB position. A gauge connected to the rod end pressure tap while the hoist control valve is in the SNUB position will show the brake cooling system pressure, which is a result of the restriction in the coolers, brakes, and hoses. The maximum pressure in the circuit should correspond to the setting of the brake oil cooler relief valve.
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Text Reference
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1 1
175
Two-stage hoist cylinders (1) are used to raise the body. Oil flows from the hoist control valve to the two hoist cylinders when the directional spool in the hoist control valve is not in HOLD. Check the condition of the body pads (2) for wear or damage. Hoist pilot pressure is required to lower the body with a dead engine. The towing pump can be used to provide the hoist pilot oil. To lower the body with a dead engine: 1. Move towing valve to TOW position 2. Turn key ON 3. Hold hoist lever in RAISE 15 seconds 4. Move hoist lever to HOLD, then FLOAT 5. Depress secondary steering switch and body will lower
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Text Reference
773F / 775F HOIST AND BRAKE COOLING SCHEMATIC Main Relief Dump Spool
From Pressure Reducing Valve
Raise Relief Valve
Dual Stage Signal Spool
Lower Relief Valve
Left Rear Brake
Lower, Float, Snub Solenoid From Brake System
RAISE Brake Cooler
Right Rear Brake
HOLD
SNUB
Hoist Pump
FLOAT
Brake Cooling Relief Valve
Orifice Plate
LOWER
Orifice Plate
Raise Solenoid
176
This illustration shows the hoist hydraulic system in the HOLD position. The hoist pump pulls oil from the hydraulic tank through the suction screen located in the rear of the tank. Oil flows from the hoist pump to the hoist control valve. When the hoist control valve is in the HOLD, FLOAT, or SNUB position, all the hoist pump oil flows through the brake oil cooler located on the right side of the engine. Oil flows from the oil cooler, through the rear brakes, and returns to the hydraulic tank. A brake cooling relief valve is located in the hoist control valve. The relief valve limits the brake oil cooling pressure when the hoist control valve is in the HOLD, FLOAT, or SNUB position. The hoist valve uses parking brake oil pressure that has been reduced by the pressure reducing valve as the pilot oil to shift the directional spool inside the hoist control valve. Oil flows from the pressure reducing valve to both ends of the hoist control valve.
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Text Reference
Pilot pressure is always always present at both ends of the directional directional spool. Two solenoid valves are used to drain the pilot oil from the ends of the directional spool, which then allows the centering springs and the pressure on the opposite end of the spool to move the spool. When the RAISE solenoid is energized, the directional spool will move toward the RAISE solenoid. The RAISE and LOWER solenoid valves constantly receive approximately 300 millivolts at a frequency of 80 Hz from the Transmission/Chassis ECM when they are in any position except HOLD. The excitation, referred to as "dither," "dither," is used used to keep the solenoids in a ready state for quick response. When the Transmission/Chassis ECM receives an input signal from the hoist lever sensor, the ECM sends an output signal current between 0 and 1.9 amps to one of the solenoids. The amount of current sent to the solenoid determines how much pilot oil is drained from the end of the directional spool and, therefore, the distance that the directional spool travels. The truck should normally normally be operated with the hoist lever in the FLOAT FLOAT position. Traveling with the hoist in the FLOAT FLOAT position will make sure the weight of the body is on the frame and the body pads and not on the hoist cylinders. The hoist valve will actually be in the SNUB position. When the hoist control valve is in the RAISE position, pump supply oil flows to the head end of the hoist cylinders. Pump supply oil also flows to the dual stage signal spool and moves moves the spool to the left. When the dual stage signal spool moves moves to the left, pump supply oil is blocked from the LOWER relief valve, and the RAISE relief valve will limit the hoist system pressure. When the hoist control valve is in the LOWER (power down), FLOAT, or SNUB position, pump supply oil flows to the rod end of the hoist cylinders. Pump supply oil is blocked from the dual stage signal spool and the spring spring holds the spool in the right right position. When the dual stage signal spool is in the right position, pump supply oil can flow to the LOWER relief valve, and hoist system pressure is controlled by the LOWER relief valve. An orifice plate is installed between the upper hose and the rod end port on both hoist cylinders. The orifice plate prevents cavitation of the the cylinders when the body raises faster faster than the pump can supply oil to the cylinders (caused by a sudden shift of the load).
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6
7
4
5
2
1
177 BRAKE SYSTEM
Two separate brake systems are used on the 773F/775F trucks. The two brake systems are the service/retarder brake system system and the parking/secondary parking/secondary brake system. The parking/secondary brakes are spring engaged and hydraulically released. The service/retarder brakes are hydraulically engaged and spring released. The braking system is also equipped with a Brake ECM that controls the braking system functions, including the Automatic Retarder Control (ARC) and the Traction Control System (TCS). The air system on the previous model trucks has been completely removed. The main components in the braking system are: - Brake charg charging ing pump pump (1)
- Diver Diverter ter (towing) (towing) valve valve (5)
- Accumul Accumulator ator charging charging valve (2) (2)
- Brake oil filter filter (6)
- Brake accumul accumulators ators (3)
- TCS val valve ve (7) (7)
- Servic Servicee brake valve (4) (4)
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178
The rear brakes on the 773F/775F trucks are oil cooled. Shown is a cutaway illustration illustration of an oil cooled brake assembly assembly.. The brakes are environmentally sealed sealed and adjustment free. Oil continually flows through the brake discs for cooling. Duo-Cone seals prevent the cooling oil from leaking to the ground or transferring transferring into the axle housing. The wheel bearing adjustment must be maintained to keep the Duo-Cone seals from leaking. The smaller piston (yellow) is used to engage the secondary and parking brakes. The parking brakes are spring engaged and hydraulically released. The larger piston (purple) is used to engage the service and retarder brakes. The service and retarder brakes are engaged hydraulically and released by spring force.
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179
The front brakes are a disc and caliper design. The brake caliper assemblies are fastened fastened to the spindle and do not rotate. The brake disc is fastened to the the wheel and rotates with the wheel. Air can be bled from the front brakes through the bleed valves. During brake application, hydraulic oil from the brake cylinders forces the brake pistons against the brake carrier linings (brake pads). pads). The brake linings are forced against the the disc to stop the rotation of the wheel.
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Text Reference
2 1
180
2 1
181
The brake charging pump (1) and the hoist pump (2) are mounted to the pump drive gear on the left rear side of the the engine. The 773F/775F brake system accumulators are charged by the brake charging pump, which supplies oil to the accumulator charging cha rging valve.
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2 1
3
182
The brake system filter (1) is mounted to a bracket on the inside of the left frame rail. The brake filter includes a filter bypass switch (2), which sends a signal to the Brake ECM if the filter is restricted. The Brake ECM sends a signal to the monitoring system, which illuminates the brake system-check indicator lamp. An S•O•S tap is located next to the brake filter.
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2
4 183
3 5 1
3 4
184
2
1
The accumulator charging valve (1) is located below the right frame rail bolted to a mounting bracket that also supports the brake accumulators. The accumulator charging valve directs oil to the brake accumulators, brake oil cooler, and the tank. Once the accumulators are charged, the excess oil flow is sent to cool the rear brakes before returning to the tank. The Brake ECM monitors the pressure in the service brake accumulators with the brake accumulator pressure switch (2). If the pressure in the service brake accumulators is low, the Brake ECM will signal the monitoring system to turn on the brake system-check indicator lamp. A relief valve (3) limits the pressure in the brake charging circuit.
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Text Reference
A pressure tap (4) on the line between the brake charging pump and the accumulator charging valve is used to check the charge oil pressure from the pump. The pressure tap (5) on the charging valve is used to check the oil pressure in the brake accumulators. Cut-in and cut-out pressure can be adjusted with a screw that can be accessed by removing a plug (6).
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Text Reference
185
The accumulator charging valve maintains the pressure in the accumulators at a constant rate while the engine is running. If the machine has lost power or the hydraulic pump has failed, the pressure in the accumulators will permit several applications of the service brakes. This illustration shows the accumulator charging valve in the CUT-IN position. When the accumulator oil pressure decreases below a certain point, the accumulator charging valve reaches the cut-in pressure setting. The pressure decrease allows spring force to move the cut-in/cut-out spool to the left and oil flows to the right end of the unloading valve. The orifice in the unloading valve restricts the pump flow to the brake cooling system. Oil flow to the brake accumulators increases and the accumulators are charged. The accumulator oil pressure switch sends a signal to the Brake ECM to alert the operator when the brake oil pressure drops below the minimum operating pressure.
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This illustration shows the accumulator charging valve in the CUT-OUT position. When the accumulator oil pressure increases to the cut-out pressure setting, the increased pressure causes the cut-in/cut-out spool to move right against spring force. Oil at the right end of the unloading valve flows to the tank. Oil pressure on the left end of the unloading spool overcomes the decreased oil pressure on the right end of the spool and spring force. Most of the brake charging pump oil now flows to the brake cooling system. The check valve prevents high accumulator oil pressure from flowing to the brake cooling system. The accumulator charging valve remains in the CUT-OUT position until the pressure in the accumulators decreases to the cut-in pressure setting. The pressure relief valve regulates the oil pressure in the brake circuit. Any excess oil that is not required by the brake cooling system or the brake circuit is diverted back to the hydraulic oil tank. NOTE:
The pressure relief valve is set much higher than cut-out pressure and is only needed as a backup if cut-out fails.
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2
Text Reference
1
187
There are two brake accumulators for the 773F/775F trucks located on the right side of the truck. The service brake accumulator (1) and parking brake accumulator (2) are charged by the brake charging pump and supply the required oil flow to engage the front and rear service brakes and to release the rear parking brakes. A check valve in the circuit between the parking brake accumulator and the service brake accumulator allows only the parking brake accumulator to be charged when using the electric brake release pump.
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3
2
3 4 1 1
188
The cab brake manifold (1) is mounted below the cab on the left upper frame. The cab brake manifold contains the ARC control solenoid (2) and the front service brake solenoid (3). The ARC control solenoid is part of the ARC system. The ARC system uses the rear service brakes to automatically control the speed of the truck. The service brake pressure switch (4) is located near the cab brake manifold toward the front of the machine. The service brake pressure switch sends a signal to the Brake ECM when the service brakes are engaged. The Brake ECM will use the signal from the pressure switch to energize the stop lamp relay (located in cab) and turn on the brake lights. In a low pressure situation, the Brake ECM will signal the monitoring system to activate the brake system-check indicator.
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2 189
3
190
1
The service brake valve (1) is mounted below the floor of the operator’s cab. When the service brake pedal (2) is depressed, an internal spool directs oil flow from the service brake accumulators to the rear service brakes. The amount of oil flow to the front service brakes is determined by the Brake ECM based on a signal from the service brake pedal position sensor (3). The Brake ECM allows some oil from the brake accumulators to flow to the front brakes by controlling the position of the front brake solenoid located in the cab brake manifold.
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Text Reference
2
3
1
191
When the manual retarder lever (1) is activated, a PWM signal is sent to the Brake ECM. The Brake ECM sends a signal to the ARC solenoid. The solenoid controls the amount of oil flow to the service brakes based on the position of the retarder lever. If the ARC switch (2) is activated, the Brake ECM sends a signal to the ARC solenoid. The solenoid controls the amount of oil flow to the service brakes based upon the input signals that the Brake ECM receives from the engine speed sensor. The optional engine brake switch (3) is also an input to the Brake ECM. The Brake ECM communicates the status of the brake switch to the Engine ECM via the Cat Data Link. The Engine ECM controls the compression brake application (if equipped).
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Text Reference
2 1
192
The rear slack adjuster (1) is located above the rear differential. The slack adjuster compensates for brake disc wear by allowing a small volume of oil to flow through the slack adjuster and remain between the slack adjuster and the brake piston under low pressure. The slack adjuster maintains a slight pressure on the brake piston at all times. Brake cooling oil pressure maintains a small clearance between the brake discs. The service brake oil pressure can be tested at the tap (2) located on top of the slack adjuster.
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Text Reference
193
This illustration shows sectional views of the slack adjuster when the brakes are RELEASED and when the brakes are ENGAGED. When the brakes are ENGAGED, oil from the brake cylinder enters the slack adjuster and the two large pistons move outward. Each large piston supplies oil to one wheel brake. The large pistons pressurize the oil to the service brake pistons and ENGAGE the brakes. Normally, the service brakes are FULLY ENGAGED before the large pistons in the slack adjuster reach the end of their stroke. As the brake discs wear, the service brake piston will travel farther to FULLY ENGAGE the brakes. When the service brake piston travels farther, the large piston in the slack adjuster moves farther out and contacts the end cover. The pressure in the slack adjuster increases until the small piston moves and allows makeup oil from the brake cylinder to flow to the service brake piston. When the brakes are RELEASED, the springs in the service brakes push the service brake pistons away from the brake discs. The oil from the service brake pistons pushes the large pistons in the slack adjuster to the center of the slack adjuster. Makeup oil that was used to ENGAGE the brakes is replenished at the brake cylinder from the makeup tank.
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The spring behind the large piston causes some oil pressure to be felt on the service brake piston when the brakes are RELEASED. Keeping some pressure on the brake piston provides rapid brake engagement with a minimum amount of brake cylinder piston travel. The slack adjusters can be checked for correct operation by opening the service brake bleed screw with the brakes RELEASED. A small amount of oil should flow from the bleed screw when the screw is opened. The small flow of oil verifies that the spring behind the large piston in the slack adjuster is maintaining some pressure on the service brake piston.
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Text Reference
2
1
194
The service brake bleed screw (1) is identified by an "S" on the brake anchor plate casting next to the screw. The parking brake bleed screw (2) is identified by a "P" on the casting. Another check to verify correct slack adjuster operation is to connect a gauge to the pressure tap on top of the slack adjuster and another gauge at the service brake bleed screw location on the brake anchor plate casting. With the service brake pedal depressed, the pressure reading on both gauges should be approximately the same. When the brakes are RELEASED, the pressure at the slack adjuster should return to zero. The pressure at the service brake bleed screw location should return to the residual pressure held on the brakes by the slack adjuster piston. If the slack adjuster residual pressure is too low, it could indicate a failed slack adjuster. High residual pressure may indicate a failed slack adjuster or warped brake discs. To check for warped brake discs, rotate the wheel to see if the pressure fluctuates. If the pressure fluctuates while rotating the wheel, the brake discs are probably warped and should be replaced. To check for brake cooling oil leakage, block the brake cooling ports and pressurize each brake assembly to a maximum of 138 kPa (20 psi). Close off the air supply source and observe the pressure trapped in the brake assembly for five minutes. The trapped pressure should not decrease.
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Text Reference
1
1
2
4
3
195
The parking brake valve (1) is located on the inside left frame rail behind the center cross member. The parking valve receives oil flow from the parking brake accumulator. Contained within the valve is a parking brake solenoid valve (2) and a purge solenoid valve (3). When the parking brake solenoid is energized by the Brake ECM, the parking brake valve directs oil flow through the TCS valve to release the rear parking brakes. There are no parking brakes on the front wheels. When the transmission shift lever is moved to PARK a signal is sent to the Brake ECM to engage the parking brakes. There is not a separate parking brake control switch. The secondary brake pressure switch (4), located to the rear of the parking brake valve, sends a signal to inform the Transmission/Chassis ECM that the secondary/parking brake is engaged. When the machine is shut down, the purge solenoid is energized by the Transmission/Chassis ECM and the purge valve drains the brake accumulators to tank.
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Text Reference
1
2
196
The parking brake pressure can be checked at the left parking brake tap (1) and at the right parking brake tap (2).
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197
The secondary brake pedal position sensor (arrow) is located on the back of the secondary brake pedal. The position sensor sends a signal to the Brake ECM indicating the position of the secondary brake pedal. The Brake ECM sends a signal to the parking brake solenoid which controls the secondary brake application at the rear brakes.
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Text Reference
198
The secondary steering/brake release/QuickEvac pump and motor are located on the front of the front frame crossmember as previously shown. The brake retract pump section (arrow) provides oil to release the parking brakes and provides hoist pilot oil for lowering the body on trucks with a dead engine.
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Text Reference
2
1 3
199
2
200
3 1
The diverter (towing) valve (1) is located on the left frame rail in front of the left front strut. The diverter valve is used to unlock the brakes for towing and must be manually shifted before towing. Once the valve is shifted, oil flow from the electric secondary steering/brake retract pump is directed to the parking brake valve to release the parking brake. The relief valve (2) limits the maximum pressure when using the brake retract pump. To release the parking brakes for service work or towing, the electric motor on the pump is energized by the brake release/secondary steering switch located in the cab.
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Text Reference
When the key start switch is turned ON, the secondary steering system is energized for three seconds to check the system. Since the towing pump is driven by the same electric motor as the secondary steering pump, the diverter valve allows the towing pump oil to flow directly to the hydraulic tank during the secondary steering test. To shift the diverter valve, loosen the two diverter valve clamp bolts and slide the plate and the spool to the left. After the spool is shifted, tighten the diverter valve clamp bolts. When the electric motor is energized, supply oil can flow from the towing pump, through the diverter valve, to the parking brake valve. NOTE:
With the engine shutoff, the purge solenoid will divert the brake release pump supply oil to the tank. Therefore, when towing the machine, the return lines from the parking brake valve and traction control valve must be capped to block the brake release pump supply oil from flowing to the tank.
The brake release pump is also used to provide pilot oil to lower the body when the engine is off. Located next to the diverter valve is the pressure reducing valve (3). The pressure reducing valve reduces the parking brake system oil pressure for the hoist pilot system.
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Text Reference
773F / 775F HOIST AND BRAKE COOLING SCHEMATIC Main Relief Dump Spool
From Pressure Reducing Valve
Raise Relief Valve
Dual Stage Signal Spool
Lower Relief Valve
Left Rear Brake
Lower, Float, Snub Solenoid From Brake System
RAISE Brake Cooler
Right Rear Brake
HOLD
SNUB
Hoist Pump
FLOAT
Brake Cooling Relief Valve
Orifice Plate
LOWER
Orifice Plate
Raise Solenoid
201
This schematic shows the oil flow through the hoist and brake cooling system on the 773F/775F trucks. The hoist valve and the brake accumulator charging valve supply oil to the brake cooler and the rear brakes. The pressure in the brake cooling system is limited by the brake cooling relief valve located in the hoist valve. The relief valve is usually needed only when the brake cooling oil is cold. When brake cooling oil is at operating temperature, the brake cooling oil pressure is usually much lower than the setting of the oil cooling relief valve.
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Text Reference
202
The brake oil cooler (arrow) is located on the right side of the engine. Engine coolant from the water pump flows around the brake oil cooler and back to the cylinder block. The engine coolant transfers the heat from the brake oil system to the engine coolant. Oil from the brake cooling pump flows through a screen (not shown) before flowing through the brake oil cooler.
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Text Reference
203
Brake cooling oil pressure can be tested at the two taps (arrows) located in the brake cooling oil tubes. One tap is located on the brake cooling inlet tube and another tap is located on the brake cooling outlet tube. The pressure measured at the brake inlet tube (from the oil coolers) will always be higher than the pressure measured at the brake outlet tube. A brake oil temperature sensor is located in a brake oil cooling tube on the truck. The brake oil temperature sensor sends a signal to the Brake ECM indicating brake oil temperature. The Brake ECM will send a signal over the Cat Data Link, which informs the monitoring system to display the temperature on the brake temperature gauge. The most common cause of high brake cooling oil temperature is operating the truck in a gear range which is too high for the grade and not maintaining a high enough engine speed. The engine speed should be maintained at approximately 1900 rpm during long downhill hauls. Make sure the oil cooling relief valve is not stuck open. Also, make sure the pistons in the slack adjuster are not stuck and holding too much pressure on the brakes.
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Text Reference
204
This schematic shows the major components of the brake hydraulic system. Oil is drawn from the hydraulic tank by the brake charging pump. Oil flows through the brake filter to the accumulator charging valve. The accumulator charging valve directs supply oil to the brake accumulators. The accumulator charging valve also controls the cut-in and cut-out pressure. When the accumulators are charged, the charging valve will direct excess pump flow to the brake cooling system. The service brake accumulator provides oil flow to the service brake control valve. Oil also flows to the ARC control solenoid and front brake solenoid. When the operator depresses the service brake pedal, the service brake control valve directs pump flow to the rear service brakes to stop the truck. The front brakes are only engaged when the Brake ECM energizes the front brake solenoid. The Brake ECM energizes the front brake solenoid when the service brake pedal is depressed if the front brake switch in the cab is ON. The Brake ECM controls the modulation of the ARC solenoid and front brake solenoid, which controls truck braking when the ARC system is ON.
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Text Reference
Oil from the parking brake accumulator flows to the parking brake valve and the towing diverter valve. When the parking brake is activated, the supply oil for releasing the parking brakes is directed to the tank and the parking brakes are engaged by spring force. When the parking brake solenoid is energized (parking brake de-activated), the parking brake valve directs oil to the TCS valve. The pressure reducing valves in the TCS valve direct oil to release the parking brakes. The diverter valve, under normal operation, is closed and blocks the oil flow from the electric brake retract pump. If the truck is to be towed with a dead engine, the diverter valve must be shifted manually. When manually shifted, the diverter valve directs oil flow from the electric brake retract pump to the parking brake valve to release the rear brakes.
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Text Reference
205
Brake Electronic Control System
The 773F/775F Trucks are equipped with a Brake ECM for controlling the parking brake and front service brake applications, the ARC system, and the TCS. The following two possible service brake application arrangements can be installed on a truck: - ARC only - ARC and TCS The Brake ECM receives information from various input components such as the engine speed sensor, the service brake pedal position sensor, the ARC switch, and the wheel speed sensors. Based on the input information, the Brake ECM controls the front service brake application when the service brake pedal is depressed or the rear service brake application when the ARC system is activated. The Brake ECM also controls when the parking brakes should engage for the TCS and parking brake application when the parking brake is manually activated.
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Text Reference
Output components include the ARC solenoid, the front service brake solenoid, the TCS selector and proportional solenoids, and the parking brake solenoid. The compression brake switch is also an input to the Brake ECM. When the compression brake switch is activated, the Brake ECM sends a signal over the Cat Data Link to the Engine ECM. The Engine ECM controls the engine compression brake, which was covered earlier in the presentation.
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Text Reference
206
The Brake ECM (arrow) is located in the compartment at the rear of the cab. The Brake ECM performs the brake control functions, and controls the ARC system and TCS system. The Brake ECM is an A4M1 module with two 70-pin connectors. The Brake ECM communicates with the Engine ECM, Transmission/Chassis ECM, and monitoring system over the CAT Data Link and can communicate with some attachments over the CAN Datalink.
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Text Reference
207
When the service brake pedal is depressed, the service brake valve directs oil from the service brake accumulator to the rear brakes and sends a PWM signal to the Brake ECM via the service brake pedal position sensor. The Brake ECM signals the front service brake solenoid to direct oil from the service brake accumulator to the front brakes if the front brake lockout switch in the cab is OFF. If the lockout switch is ON, the Brake ECM de-energizes the front service brake solenoid. Oil flow to the front brakes is blocked and only the rear brakes are used to stop the truck. NOTE:
Oil flow to the front and rear brakes may not be proportional. When the pedal is initially depressed, more oil is directed to the rear brakes. As the pedal is depressed farther more oil is sent to the front brakes in proportion to the rear until full front brake pressure is present at full pedal travel.
The Brake ECM also de-energizes the ARC solenoid when the ARC switch in the cab is OFF and the manual retarder lever is in the NEUTRAL position. The manual retarder lever also controls the service brake application using the ARC solenoid.
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Text Reference
When the retarder lever is moved, a PWM signal is sent to the Brake ECM. The Brake ECM de-energizes the front service brake solenoid. Oil flow to the front brakes is blocked and only the rear brakes are used to stop the truck with the retarder lever.
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Text Reference
AUTOMATIC RETARDER CONTROL (ARC)
To Rear Service Brakes ARC Solenoid
Service Brake Valve
Engin e Speed Sensor
From Service Brake Accumulator
Brake ECM
Front Service Brake Solenoid
ARC ON / OFF Switch To Front Service Brakes
Cab Manifold
208
Automatic Retarder Control (ARC)
The ARC system receives signals from several switches and sensors. The main inputs to the Brake ECM for the ARC system are the ARC switch and engine speed sensor. The Brake ECM analyzes the various input signals and sends output signals to the ARC solenoid. The ARC system function is to modulate truck braking (retarding) when descending a long grade to maintain a constant engine speed. The ARC system engages the rear service brakes. If the ARC switch is moved to the ON position, the ARC system will be activated if the throttle pedal is not depressed and the parking/secondary brakes are RELEASED. The ARC system is disabled when the throttle is depressed or when the parking/secondary brakes are ENGAGED. The ARC is set at the factory to maintain a constant engine speed of 2285 rpm (engine speed setting is programmable from 2235 to 2285 rpm). When the ARC initially takes control of retarding, the engine speed may oscillate out of the ± 50 rpm target, but the engine speed should stabilize within a few seconds.
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Text Reference
For proper operation of the ARC system, the operator needs only to activate the control with the ARC switch and select the correct gear for the grade, load, and ground conditions. The ARC system is designed to allow the transmission to upshift to the gear selected by the shift lever. After the transmission shifts to the gear selected by the operator and the engine speed exceeds 2285 rpm, the ARC system will apply the retarder as needed to maintain a constant engine speed. The ARC system also provides engine overspeed protection. If an unsafe engine speed is reached, the ARC will engage the brakes, even if the ARC switch is in the OFF position and the throttle is depressed. Trucks approaching an overspeed condition will sound a horn and activate a light. If the operator ignores the light and horn, the ARC will engage the retarder. If the engine speed continues to increase, the Transmission/Chassis ECM will either upshift (one gear only above shift lever position) or unlock the torque converter (if the shift lever is in the top gear position). The ARC also provides service personnel with enhanced diagnostic capabilities through the use of onboard memory, which stores possible faults, solenoid cycle counts, and other service information for retrieval at the time of service.
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Text Reference
209
Traction Control System (TCS)
The Traction Control System (TCS) uses the rear parking/secondary brakes (spring engaged and hydraulically released) to decrease the revolutions of a spinning wheel. The TCS allows the tire with better underfoot conditions to receive an increased amount of torque. The TCS is controlled by the Brake ECM and operates the same as the D and E series Trucks. The Brake ECM monitors the drive wheels through four input signals: one at each drive axle, and two at the transmission output shaft. When a spinning drive wheel is detected, the Brake ECM sends a signal to the selector and proportional valves which ENGAGE the brake of the affected wheel. When the condition has improved and the ratio between the right and left axles returns to 1:1, the Brake ECM sends a signal to RELEASE the brake.
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Text Reference
The service brake pressure switch provides an input signal to the Brake ECM from the Transmission/Chassis ECM through the CAT Data Link and performs two functions: 1. When the service brakes or retarder are ENGAGED, the TCS function is stopped. 2. The service brake pressure switch provides the input signal needed to perform a diagnostic test. When the TCS test switch and the retarder lever are ENGAGED simultaneously, the TCS will engage each rear brake independently. Install two pressure gauges on the TCS valve, and observe the pressure readings during the test cycle. The left brake pressure will decrease and increase. After a short pause, the right brake pressure will decrease and increase. The test will repeat as long as the TCS test switch and the retarder lever are ENGAGED. The TCS valve has left and right brake release pressure taps. When the proportional solenoid is ENERGIZED, Cat ET will show 68% when the brake is FULLY ENGAGED. NOTE:
During the diagnostic test, the parking/secondary brakes must be released.
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Text Reference
210
Shown is the right rear wheel speed sensor (arrow) looking toward the rear of the truck. The TCS monitors the drive wheels through four input speed signals: one at each drive axle, and two at the transmission output shaft. The transmission output speed sensors monitor the ground speed of the machine and provide input signals to the Brake ECM through the CAT Data Link. The TCS uses the transmission output speed sensors to disable the TCS when ground speed is above 19.3 km/h (12 mph).
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Text Reference
2 1
3 3
211
The TCS valve is mounted inside the left frame rail toward the rear of the machine. Two solenoids are mounted on the valve. Electrical signals from the Brake ECM cause the selector solenoid valve (1) to shift and select either the left or right parking brake. If the selector valve shifts to the left parking brake hydraulic circuit, the control oil is drained. The left reducing spool of the control valve can then shift and engage the parking brake. The proportional solenoid valve (2) controls the volume of oil being drained from the selected parking brake control circuit. The rate of flow is controlled by a signal from the Brake ECM. The pressure taps (3) can be used to test the left and right brake release pressures when performing diagnostic tests on the TCS. At HIGH IDLE, the pressure at the taps in the TCS valve will be approximately 138 kPa (20 psi) less than the brake release pressure tested at the wheels. The pressure taps are also used to provide parking brake dragging information to the service technician. If the parking brakes are released, as sensed by the secondary brake pressure switch on the parking brake control valve, and parking brake pressure is below 3445 kPa (500 psi), a parking brake dragging event will be logged in the Brake ECM. The event can be viewed with Cat ET.
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Text Reference
212
This illustration shows the TCS valve with the engine running and the brakes RELEASED. With the engine running, oil flows from the parking brake accumulator to the parking brake valve. When the operator moves the transmission lever out of the PARK position, the Brake ECM energizes the parking brake solenoid which directs oil flow to the TCS valve. In the TCS valve, oil flows through a screen and orifices to the selector solenoid and the brake reducing valves. When the TCS is not activated, the oil is blocked at the selector solenoid. Oil pressure moves the brake reducing solenoids to the left and oil from the brake charging pump is directed to the parking brakes. The parking brakes are RELEASED.
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Text Reference
01/07
213
This illustration shows the TCS valve with the engine running and the left brake ENGAGED. When signals from the sensors indicate that the left wheel is spinning 60% faster than the right wheel, the Brake ECM sends a signal to the selector solenoid valve and the proportional solenoid valve. The selector solenoid valve shifts up to open a passage between the right end of the left brake pressure reducing valve and the proportional solenoid valve. The pressure reducing valve provides signal oil to the drain ball check which allows oil from the TCS valve to return to the tank. The proportional solenoid valve opens a passage from the selector solenoid valve to drain through the drain ball check. The proportional solenoid valve also controls the rate at which the oil is allowed to drain. Control circuit oil drains through the selector valve and enters the proportional valve.
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Text Reference
The reducing valve spool for the left parking brake shifts and blocks oil flow to the parking brake. Oil in the left parking brake control circuit begins to drain and the left parking brake begins to ENGAGE. The left brake orifice restricts the flow of oil from the parking brake valve. When the signals from the sensors indicate that the left wheel is no longer spinning, the Brake ECM stops sending signals to the selector solenoid and the proportional solenoid. The selector solenoid valve and proportional solenoid valve block the passage to drain and allow the control circuit pressure to increase. The left brake reducing valve spool shifts to the left and blocks the passage to drain. Parking brake oil is directed to the left parking brake and the brake is RELEASED.
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Text Reference
214
CONCLUSION
This presentation has provided a basic introduction to the Caterpillar 773F/775F Off-highway Trucks. All the major component locations were identified and the major systems were discussed. When used in conjunction with the service manual, the information in this package should permit the technician to analyze problems in any of the major systems on these trucks.
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01/07
VISUAL LIST
1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41.
Model view (right side) Model view (left side) Model view (front 775F) Model view (rear 775F) Walk around inspection Every 10 hours or daily inspection Front wheel bearing Front suspension grease outlet fitting Brake linings Primary fuel filter Dual engine oil filters Hoist and brake hydraulic tank Final drives Rear suspension cylinders Body up retaining pins Fuel level sight gauge Torque converter and transmission charging filter S•O•S tap Brake oil filer Oil filter bypass switch Manual engine shutdown switch Battery disconnect switch Engine disconnect switch Engine lockout control switch Jacket water coolant sight gauge Radiator cap Steering system hydraulic tank sight gauge Steering system oil filter Air intake system components Windshield washer reservoir Operator's compartment 10 hour or daily checks Cab air filter Operator's station Truck Production Management System (TPMS) Front dash panel (left side) Retarder lever Shift console Overhead console Floor pedals Fuse panels 773/775/f Electronic System block diagram
42. Instrument cluster and VIMS/Advisor display panel 43. Instrument cluster (front dash panel) 44. Instrument cluster gauges and indicators 45. Messenger Display Module 46. Messenger menu screen 47. Performance screen submenu 48. Performance menu 49. Total menu selections 50. Settings menu selection 51. Service menu selection 52. Service menu diagnostic events 53. Service mode password menu 54. Advisor/VIMS graphical display module 55. Introduction screen after machine startup 56. Main screen 57. Transmission/Chassis ECM "pop-up" warning screen 58. Advisor home menu selections 59. Operator menu 60. Select profile screen 61. Operator menu selection 62. Service menu 63. Calibrations submenu 64. Service menu - diagnostics submenu 65. Service menu - calibrations submenu 66. Service menu - service parameters submenu 67. Settings menu 68. Settings menu - display setup 69. Payload menu 70. Payload state - loading 71. Monitor menu 72. Monitor - Parameter Screen 1 73. Grade menu 74. Grade menu - percentage of the grade value 75. Service mode menu 76. Service Mode - enable or disable 77. C27 engine with ACERT™ technology 78. Engine ECM system diagram 79. Engine ECM 80. Coolant temperature sensor 81. Crankshaft speed/timing sensor
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VISUAL LIST
82. 83. 84. 85. 86. 87. 88.
Cam speed/timing sensor Loss of engine speed/timing signal Throttle position sensor Prelubrication (QuickEvac) pump Ether start system High coolant temperature derate C11-C32 engine intake manifold temperature derate 89. Low oil pressure 90. Air inlet restriction derate 91. Fuel temperature derate 92. Fuel filter restriction derate - Fuel Temp above 30° V (86° F) and fuel pressure above 138 kPa (20) psi 93. Engine compression brake 94. Engine compression brake hydraulic circuit - compression brake OFF 95. Engine compression brake schematic 96. Arc power and compression braking level vs time 97. Cooling system 98. Water pump 99. Cooling system flow 100. Engine oil system 101. Fuel system 102. Fuel transfer pump 103. Differential fuel pressure switch 104. Fuel filter base 105. Fuel cooler 106. Low pressure fuel system 107. Trim code files 108. Injector trim file 109. Air intake and exhaust system 110. Turbocharger inlet pressure sensor 111. Turbocharger - turbine side 112. ATAAC core 113. Turbocharger outlet pressure sensor 114. Exhaust system 115. Air induction and exhaust system 116. Power train 117. Power train electronic components 118. Power train hydraulic system 119. Torque converter - converter drive 120. Torque converter - direct drive
121. Two-section power train pump 122. Torque converter lockup clutch 123. Lockup clutch modulating valve - torque converter drive 124. Lockup clutch modulating valve - direct drive 125. Torque converter and transmission charging filter 126. Filter bypass switch 127. Transmission hydraulic system NEUTRAL 128. ECPC transmission hydraulic controls 129. Transmission modulating valves 130. Engagement of transmission clutches 131. Transmission modulating valve - NO COMMANDED SIGNAL 132. Transmission modulating valve COMMANDED SIGNAL BELOW MAXIMUM 133. Transmission modulating valve COMMANDED SIGNAL AT MAXIMUM 134. Main relief valve 135. Magnetic inspection plug 136. Rear axle breather 137. Differential 138. Transmission/Chassis Electronic Control System inputs and outputs 139. Transmission/Chassis ECM 140. Transmission shift lever circuits 141. Transmission output speed sensors 142. Engine speed sensor 143. Body up switch 144. Transmission/Chassis ECM - systems controlled by ECM 145. Steering system 146. Steering system oil level sight gauge 147. Steering system oil filter 148. High pressure cut-off valve 149. Flow compensator valve 150. Steering pump - LOW PRESSURE STANDBY 151. Steering pump - MAXIMUM FLOW 152. Steering disable valve location 153. Steering disable solenoid valve
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VISUAL LIST
154. Steering valve 155. HMU for 773F/775F 156. Electric secondary steering pump and motor 157. Pump and motor assembly 158. Steering hydraulic system - LOW PRESSURE STANDBY 159. Hoist system 160. Hoist lever 161. Hoist lever position sensor 162. Hoist and brake hydraulic tank 163. Hoist and brake hydraulic tank - rear view 164. Hoist pump 165. Hoist pump pressure tap 166. Hoist control valve 167. Pressure reducing valve 168. Raise and lower solenoid valve 169. Hoist cylinder lower circuit pressure tap 170. Hoist control valve. - HOLD 171. Hoist control valve. - RAISE 172. Hoist control valve. - LOWER/POWER DOWN 173. Hoist control valve. - FLOAT 174. Hoist control valve. - SNUB 175. Two-stage hoist cylinders 176. 773/775 hoist and brake cooling schematic 177. Brake system 178. Rear brakes 179. Caliper disc brake 180. Brake charging pump 181. Hoist pump 182. Brake system filter 183. Accumulator charging valve 184. Brake ECM 185. Accumulator charging valve - CUT-IN 186. Accumulator charging valve - CUT-OUT 187. 773F/775f brake accumulators 188. Cab brake manifold 189. Service brake pedal 190. Service brake valve 191. Manual retarder lever 192. Rear slack adjuster 193. Brake slack adjuster
195. 196. 197. 198. 199. 200. 201. 202. 203. 204. 205. 206. 207. 208. 209. 210. 211. 212. 213. 214.
Parking brake valve Left parking brake tap Secondary brake pedal position sensor Brake retract pump section Diverter (towing) valve location Relief valve 773/775 hoist and brake cooling schematic Brake oil cooler Brake cooling oil pressure taps Brake hydraulic system Brake control module system diagram Brake ECM Service/retarder brake circuit - BRAKES RELEASED Automatic retarder control (ARC) Traction control system (TCS) Wheel speed sensor (right rear) Selector solenoid valve TCS valve - Engine running / BRAKES RELEASED TCS valve - Engine running / LEFT BRAKE ENGAGED Conclusion
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Text Reference
HYDRAULIC SCHEMATIC COLOR CODE Black - Mechanical connection . Seal
Red - High pressu re oil
Dark Gray - Cutaway secti on
Red/White Stripes - 1st pressure reducti on
Light Gray - Surface colo r
Red Crosshatch - 2nd reduction in pressure
White - Atmosph ere or Air (No pr ess ure)
Pink - 3rd reduction i n pressure
Purple - Pneumatic pressure
Red/Pink Stripes - Secondary source oil pressure
Yellow - Moving or activated components
Orange - Pilot, charge, or Torque Converter oil
Cat Yellow - (Restr icted u sage) Identification of components within a moving group
Orange / White Stri pes Reduced pilot, charge, or TC oil pressure
Brown - Lubricating oil
Orange Crosshatch - 2nd reduction in pilot, charge, or TC oil pressure.
Green - Tank, sump, or r eturn oi l
Blue - Trapped oil
Green / White Stri pes Scavenge Oil or Hydraulic Void
HYDRAULIC SCHEMATIC COLOR CODE
This illustration identifies the meanings of the colors used in the hydraulic schematics and cross-sectional views shown throughout this presentation.
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E D O C R O L O C C I T A M E H C S C I L U A R D Y H
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l i O e r u s s e r P h g i H d e R
l a e S . n o i t c e n n o C l a c i n a h c e M k c a l B
n o i t c u d e R e r u s s e r P t s 1 s e p i r t S e t i h W / d e R
n o i t c e S y a w a t u C y a r G k r a D
e r u s s e r P n i n o i t c u d e R d n 2 h c t a h s s o r C d e R
r o l o C e c a f r u S y a r G t h g i L
e r u s s e r P n i n o i t c u d e R d r 3 k n i P
) e r u s s e r P o N ( r i A r o e r e h p s o m t A e t i h W
e r u s s e r P l i O e c r u o S y r a d n o c e S s e p i r t S k n i P / d e R
e r u s s e r P c i t a m u e n P e l p r u P
Handout No. 1
l i O r e t r e v n o C e u q r o T r o e g r a h C , t o l i P e g n a r O
r o , e g r a h C , t o l i P d e c u d e R s e p i r t S e e r t i u h s s W e / r e P i g l n O a r C T O
s t n e n o p m o C d e t a v i t c A r o g n i v o M w o l l e Y
s t n e n o p p u o ) m o r e C G g f a o g s n U n i o v o l i d i t e t a M O c i c a g i r f n i t n i i t s t n h a e e t i i c R ( d I w r b u w L o l l n e Y w t o r a B C
, t o l i P n i n o i t c u d e R d e r n u 2 s - s h e r c P t a l i h O s s C o r T C r / o , e e g g n r a a r h O C
l i O d e p p a r T e u l B
l i O n r u t e R r o , p m u S , k n a T n e e r G
d i o V c i l u a r d y H r o - l i s O e n p o i r i t t S c e u t i S h / W e / g n n e e v e r a c G S
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Handout No. 2
Machine Daily Inspection Checklist Directions: Use this sheet and the Operation and Maintenance Manual when performing the daily inspection as part of the machine orientation lab exercise.
Place a check in the blank after the task is performed.
_____
Back-up Alarm - Test
_____
Brake, Indicators, and Gauges - Test
_____
Braking System - Test
_____
Cooling System Level - Check
_____
Differential and Final Drive Oil - Check
_____
Engine Air Filter Service Indicator - Inspect
_____
Engine Oil Level - Check
_____
Fuel Tank Water and Sediment - Drain
_____
Fuel System Water Separator - Drain
_____
Hoist, Converter, and Brake Tank Oil Level - Check
_____
Seat Belt - Inspect
_____
Secondary Steering - Test
_____
Steering System Oil Level - Check
_____
Transmission Tank Oil Level - Check
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Handout No. 3
Machine Maintenance Locations Place a check in the blank after locating the following maintenance items.
Filter Locations:
_____
Brake oil filter
_____
Steering pump oil filter (case drain)
_____
Steering system oil filter
_____
Transmission and torque converter charge oil filter
_____
Air conditioner filter
_____
Cab air filter
_____
Engine oil filters
_____
Engine air filters
_____
Engine crankcase breather
_____
Secondary fuel filter
_____
Primary fuel filter
_____
Fuel tank breather
_____
Differential and final drive breather
Sampling Valve Locations:
Sampling Port Locations:
_____
Engine oil
_____
Differential and final drive
_____
Hoist, converter, and brake oil
_____
Front wheel
_____
Transmission oil
_____
Steering system oil
What is used to take oil samples of the differential, final drive, and front wheel? _________________________________________________________________
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Handout No. 4
Instrument Cluster Component Identification
List the number of each gauge or indicator: Brake system check
Traction control system engaged
Power train system check
Retarder engaged
Action lamp
Engine coolant temperature gauge
Electrical system
Machine immobilizer
Body up
Throttle lock
Transmission in reverse
Engine rpm
High beam
Machine lockout active
Transmission oil temperature gauge
Park brake engaged
Secondary steering engaged
Check engine
Truck speed
Brake oil temperature gauge
LCD display window
Fuel level gauge
Primary steering loss
Active gear and direction
Service hour meter
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Engine Component Identification _____ Fuel injectors
Function: Location: _____ Coolant temperature sensor
Function: Location: _____ Fuel pressure sensor
Function: Location: _____ Intake manifold temperature sensors
Function: Location: _____ Atmospheric pressure sensor
Function: Location: _____ Turbo outlet (boost) pressure sensors
Function: Location:
Handout No. 5
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Engine Component Identification (continued) _____ Engine oil pressure sensor
Function: Location: _____ Speed/timing sensors
Function: Location: _____ Engine ECM
Function: Location: _____ Ground level shutdown switch
Function: Location: _____ Secondary fuel filter
Function: Location: _____ Primary fuel filter
Function: Location:
Handout No. 6
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Engine Component Identification (continued) _____ Fuel temperature sensor
Function: Location: _____ Differential fuel pressure switch
Function: Location: _____ Engine compression brake assemblies
Function: Location: _____ Air filter restriction sensors
Function: Location:
Handout No. 7
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Power Train Component Identification _____ Pump group
Function: Location: _____ Transmission and torque converter charge oil filter
Function: Location: _____ Lockup clutch modulating valve
Function: Location: _____ Torque converter outlet relief valve
Function: Location: _____ Torque converter inlet relief valve
Function: Location: _____ Torque converter outlet temperature sensor
Function: Location:
Handout No. 8
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Power Train Component Identification (continued) _____ Transmission main relief valve
Function: Location: _____ Transmission modulating valves
Function: Location: _____ Transmission oil cooler
Function: Location: _____ Transmission hydraulic oil temperature sensor
Function: Location: _____ Transmission/Chassis ECM
Function: Location: _____ Engine speed sensor
Function: Location:
Handout No. 9
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Power Train Component Identification (continued) _____ Torque converter oil temperature sensor
Function: Location: _____ Transmission input speed sensor
Function: Location: _____ Transmission output speed sensors
Function: Location:
Handout No. 10
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Steering System Component Identification _____ Steering pump
Function: Location: _____ Steering valve
Function: Location: _____ Steering disable valve
Function: Location: _____ HMU
Function: Location: _____ Steering cylinders
Function: Location: _____ Secondary steering pump
Function: Location:
Handout No. 11
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Steering System Component Identification (continued) _____ Steering tank
Function: Location: _____ Primary steering pressure switch
Function: Location: _____ Secondary steering pressure switch
Function: Location:
Handout No. 12
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Hoist System Component Identification _____ Hoist pump
Function: Location: _____ Hoist control valve
Function: Location: _____ Hoist and brake hydraulic tank
Function: Location: _____ Hoist cylinders
Function: Location: _____ Hoist lever position sensor
Function: Location: _____ Hoist raise solenoid valve
Function: Location:
Handout No. 13
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Hoist System Component Identification (continued) _____ Hoist lower solenoid valve
Function: Location: _____ Brake cooling relief valve
Function: Location:
Handout No. 14
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Brake System Component Identification _____ Brake charging pump
Function: Location: _____ Accumulator charging valve
Function: Location: _____ Brake accumulators
Function: Location: _____ Cab brake manifold
Function: Location: _____ Brake oil filter
Function: Location: _____ Rear slack adjuster
Function: Location:
Handout No. 15
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Brake System Component Identification (continued) _____ Service brake valve
Function: Location: _____ Retarder lever
Function: Location: _____ Parking brake valve
Function: Location: _____ TCS valve
Function: Location: _____ Service brake pedal position sensor
Function: Location: _____ Secondary brake pedal position sensor
Function: Location:
Handout No. 16
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Brake System Component Identification (continued) _____ Brake retract pump
Function: Location: _____ Diverter (towing) valve
Function: Location: _____ Brake oil cooler
Function: Location: _____ Brake ECM
Function: Location: _____ Accumulator oil pressure switch
Function: Location: _____ TCS test switch
Function: Location:
Handout No. 17
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Brake System Component Identification (continued) _____ ARC switch
Function: Location: _____ Brake compression switch
Function: Location: _____ Front brake lockout switch
Function: Location: _____ Rear wheel speed sensors
Function: Location:
Handout No. 18
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Handout No. 19
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Handout No. 20
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Handout No. 21
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Handout No. 22
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Handout No. 23
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Handout No. 24
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Handout No. 25
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Handout No. 26
Posttest 1. When the engine lockout mode is activated, which of the following conditions exist: A. B. C. D.
engine starter is disabled secondary steering is disabled prelube function is disabled All of the above
2. The air conditioner filter is located: A. B. C. D.
on on on on
the the the the
left side of the cab right side of the cab front of the cab rear of the cab
3. The monitoring system includes how many warning categories A. B. C. D.
2 3 4 5
4. How many main menus are available for navigation on the Messenger menu screen? A. B. C. D.
3 4 5 6
5. Which of the following Messenger menus is used to determine when scheduled maintenance is required? A. B. C. D.
Performance menu Totals menu Settings menu Service menu
6. What information is NOT displayed when viewing diagnostic events on the Messenger display panel? A. B. C. D.
SRC (Source ID) Code OCC (number of occurrences) Parameter
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Handout No. 27
Posttest (continued) 7. When a "pop-up" warning screen is displayed on the Advisor display, which of the following is true? A. B. C. D.
Acknowledging the warning will clear the warning from the ECM's memory Acknowledging the warning will only clear the warning from the Advisor screen If the warning is acknowledged the warning no longer remains active None of the above
8. The calibrations menu in the Advisor Monitoring System allows calibration of which of the following: A. B. C. D.
truck payload injectors pressure sensors hoist solenoid valve
9. The monitor menu option in the Advisor Monitoring System allows the user to view how many parameters at one time? A. B. C. D.
1 2 3 4
10. Each compression brake assembly controls how many cylinders? A. B. C. D.
1 2 3 4
11. When the Engine ECM commands a MEDIUM braking level, the compression brake is activated for how many cylinders? A. B. C. D.
4 6 8 12
12. Pilot oil used to actuate the hoist solenoid valves is supplied by the: A. B. C. D.
pressure reducing valve parking brake release filter hoist pump lockup clutch valve oil circuit
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Handout No. 28
Posttest (continued) 13. Which of the following components is located on top of the transmission planetary gears? A. B. C. D.
Transmission main relief valve Transmission modulating valves Transmission hydraulic oil temperature sensor All of the above
14. Which of the following sensors checks the speed of the drive shaft to the speed of the engine? A. B. C. D.
Engine speed sensor Transmission input speed sensor Transmission output speed sensors Torque converter output speed sensor
15. When the machine lockout switch is activated, which of the following actions occurs? A. B. C. D.
HMU oil flow is blocked Steering pump is disabled Steering disable solenoid valve is energized All of the above
16. Which of the following is not installed on 773F/775F trucks? A. B. C. D.
Brake cooling pump Brake oil coolers Brake cooling relief valve All of the above
17. The ARC system uses the rear service brakes and the ______________________ to automatically control truck speed. A. B. C. D.
TCS parking brakes front caliper type brakes None of the above
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Handout No. 29
Posttest (continued) 18. The front service brake solenoid directs oil to the front service brakes. What component directs oil to the rear service brakes? A. B. C. D.
Service brake valve ARC solenoid Diverter valve Both A and B
19. Oil is provided to the diverter valve by the: A. B. C. D.
brake cooling pump service brake accumulators parking brake accumulator hoist pump
