Service Training
Update 97 September 1997
TECHNICAL PRESENTATION
769D/771D/773D/775D UPDATE OFF-HIGHWAY TRUCKS PRELIMINARY INFORMATION This document is provided for your reference only. It may not be reproduced for use by others without the authorization of East Peoria Service Training.
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TABLE OF CONTENTS
INTRODUCTION ........................................................................................................................5 WALK-AROUND INSPECTION ................................................................................................9 OPERATOR'S STATION............................................................................................................21 Caterpillar Monitoring System .............................................................................................21 Vital Information Management System (VIMS) ..................................................................37 POWER TRAIN .........................................................................................................................42 Power Train Components......................................................................................................42 Power Train Hydraulic System .............................................................................................44 Transmission and Chassis Control (EPTC III) .....................................................................55 STEERING SYSTEM ................................................................................................................62 HOIST SYSTEM ........................................................................................................................76 AIR SYSTEM AND BRAKES ..................................................................................................90 Brake Systems.......................................................................................................................92 INTEGRATED BRAKE SYSTEM (IBC) ................................................................................106 Automatic Retarder Control (ARC)....................................................................................109 Traction Control System (TCS) ..........................................................................................113 CONCLUSION.........................................................................................................................115
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INSTRUCTOR NOTES
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INSTRUCTOR NOTES
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769D/771D/773D/775D OFF-HIGHWAY TRUCKS
c 1998 Caterpillar Inc.
1
INTRODUCTION ¥ 3408E and 3412E engines
The 769D and 771D update trucks are equipped with a Caterpillar 3408E engine and the 773D and 775D update trucks are equipped with a Caterpillar 3412E engine. These engines utilize the Hydraulic Electronic Unit Injection (HEUI) system for power, reliability and economy with reduced sound levels and low emissions.
¥ Engine power ratings
The engine power ratings for the update trucks are: 769D/771D--362 kW (485 flywheel hp) 773D--485 kW (650 flywheel hp) 775D--517 kW (693 flywheel hp)
¥ Load carrying capacity
¥ Fuel tank
The load carrying capacities and the Gross Machine Weights (GMW) of the update trucks are: 769D--36.8 Metric tons (40.6 tons) @ 68182 kg (150,000 lbs.) GMW 771D--40.0 Metric tons (44.1 tons) @ 73970 kg (163,100 lbs.) GMW 773D--52.3 Metric tons (57.7 tons) @ 92530 kg (204,000 lbs.) GMW 775D--62.6 Metric tons (69.1 tons) @ 106594 kg (235,000 lbs.) GMW Shown is the left side of a 775D update truck. The fuel tank is located on the left side of the truck. On D-series pre-update trucks, the fuel tank is located on the right side of the truck.
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¥ Brake system components located on right platform
Shown is the right side of a 775D update truck. The service and retarder air tanks, the brake master cylinders, the relay valves and the brake oil makeup tank are located on the right platform near the steering tank and the engine air filters.
¥ Main hydraulic tank:
The main hydraulic tank is also visible. The hydraulic tank supplies oil for the hoist system and the brake system.
- Hoist system - Brake system
¥ Torque converter case used as sump for converter and transmission
On the D-series pre-update trucks, torque converter oil is also supplied from the main hydraulic tank. A transmission oil supply tank is located in front of the main hydraulic tank. The D-series update trucks now use the torque converter case as the supply tank for the torque converter and the transmission.
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775D update truck
Shown is the front of a 775D update truck. The 773D and 775D update trucks use a conventional radiator core. All other Caterpillar Off-highway Trucks use a folded-core style radiator.
¥ Radiator cores
The folded-core style radiator provides the convenience of repairing or replacing smaller individual cores. The conventional radiator core requires repair or replacement of a large single core.
- folded-core - conventional core
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¥ Truck body options: - 12 degree flat floor - Dual-slope
Shown is the rear of a 775D update truck. Two body options are available for the D-series update trucks: - A 12 degree flat floor design that provides uniform load dumping, excellent load retention and a low center of gravity. - A dual-slope design with a "V" bottom main floor to reduce shock loading, center the load and reduce spills. All internal wear surfaces of the truck bodies are made with 400 Brinell hardness steel. All attachment body liners are also made with 400 Brinell hardness steel. The external components of the bodies are made of steel with a yield strength of 6205 bar (90000 psi).
¥ Rear suspension cylinders
The rear suspension cylinders absorb bending and twisting stresses rather than transmitting them to the main frame.
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AIR FILTERS AND PRECLEANERS
STEERING AIR TRANSMISSION OIL RESERVOIRS AND TORQUE CONVERTER OIL
HOIST AND BRAKE OIL
BATTERIES DISCONNECT SWITCH PRIMARY FUEL FILTER/ WATER SEPARATOR SUSPENSION CYLINDERS
RADIATOR ENGINE OIL
SEAT BELTS SECONDARY STEERING TEST BRAKE TESTS INDICATORS AND GAUGES BACKUP ALARM TEST
AIR RESERVOIR
FUEL TANK
MAINTENANCE 10 HOURS/DAILY
775D
SUSPENSION CYLINDERS
5 WALK-AROUND INSPECTION ¥ Maintenance - 10 hours/daily
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 and cracks in frame structures - Suspension cylinders: Measure/recharge - Primary fuel filter/water separator: Drain moisture - Transmission and torque converter oil: Check level - Hoist and brake cooling oil: Check level - Fuel tank: Drain moisture - Radiator: Check level and radiator core plugging - Steering system oil: Check level - Air reservoirs: Drain moisture - Engine crankcase oil: Check level - Brakes: Check operation - Indicators and gauges: Test operation - Seat belt: Inspect - Back-up alarm: Test operation - Secondary steering: Test operation
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1. Transmission and torque converter oil level sight gauges
Supply oil for the transmission and the torque converter is contained in the torque converter case. Sight gauges (1) are used to check the oil level for the transmission and the torque converter.
2. Transmission and torque converter oil fill tube
Transmission and torque converter oil is added at the fill tube (2).
¥ Transmission and torque converter oil fill procedure
When filling the transmission and torque converter oil sump after an oil change, fill the sump with oil to the top of the upper sight gauge. Crank the engine for approximately 15 seconds. The oil level will decrease as oil fills the transmission and torque converter system. If the engine starts, do not allow it to run for more than 15 seconds. Add more oil to the sump 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. Start the engine and warm the transmission and torque converter oil. Add more oil to the sump as required to raise the transmission and torque converter oil level to the FULL WARM mark with the engine running.
NOTICE Failure to correctly fill the transmission and torque converter oil sump after an oil change may cause transmission clutch damage.
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¥ Use only TDTO oil
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Use only Transmission Drive Train Oil (TDTO) with a specification of (TO-4) or newer. - TDTO TO-4 provides maximum frictional capability required for clutch discs used in transmissions and torque converters. - Increases rimpull because of reduced slippage. - Use only mono-viscosity (straight weight) oils. Multi-viscosity oils use viscosity improvers which, when subjected to shearing situations, are reduced to the lower weight rating. For example, when a 10W-30 oil is used in a sheer condition, after time the oil will only perform to 10W specifications. - Never use engine oil in transmissions. Engine oils are formulated to minimize friction. Oils used in transmissions and torque converters must allow adequate friction to reduce slippage.
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¥ Hoist and brake hydraulic tank 1. Oil level sight gauge door ¥ Use only TDTO oil
Shown is the hoist and brake hydraulic tank. The oil level is checked by opening the small door (1) and looking through 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. Use only Transmission Drive Train Oil (TDTO) with a specification of (TO-4) or newer. - TDTO TO-4 provides maximum frictional capability required for clutch discs used in the brakes. - Increases brake holding capability by reducing brake slippage. - Controls brake chatter.
2. Breather
Check the hoist and brake hydraulic tank breather (2) for plugging (cover removed for visibility). Clean the filter if plugged. If oil is flowing from the filter, the hoist and brake hydraulic tank may be overfilled.
3. Return screen cover
Hoist and brake cooling oil returns to the hydraulic tank through a screen located below cover (3).
4. Towing valve
The diverter (towing) valve (4) is used when it is necessary to release the parking brakes for towing with a dead engine. The towing valve will be discussed in more detail in the Air System and Brakes section of this meeting guide.
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8 ¥ Fuel tank 1. Fuel level sight gauge
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.
¥ Fuel level sender
A fuel level sender is located on the fuel level sight gauge. The fuel level sender provides input signals to the Caterpillar Monitoring System or the attachment Vital Information Management System (VIMS) which informs the operator of the fuel level.
¥ Fuel information
The percentage of sulfur in the fuel will affect the engine oil recommendations. The following is a summary of fuel sulfur and oil recommendations: 1. Use API CG-4 performance oils. 2. With fuel sulfur below 0.5%, any API CG-4 oils will have a sufficient Total Base Number (TBN) for acid neutralization. 3. For fuel sulfur values above 0.5%, the new oil TBN should be a minimum of 10 times the fuel sulfur. 4. When 10 times the fuel sulfur exceeds the oil TBN, reduce the oil change interval to about 1/2 the normal change interval.
2. Condensation drain valve
Open the drain valve (2) to remove condensation from the fuel tank.
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1. Parking brake retraction filters
Shown is the location of the parking brake retraction filters (1). Oil flows from the parking brake retraction pump through the parking brake retraction filters to the parking brake retraction valve. Oil flows from the parking brake retraction valve to the parking brake piston in the rear brakes when the parking brakes are released.
¥ Parking brake retraction oil used as hoist pilot oil
Parking brake retraction supply oil also flows to the hoist control valve and is used as pilot oil to shift the hoist directional spool.
2. Hoist and brake oil S¥O¥S tap
Hoist and brake oil samples can be taken at the Scheduled Oil Sampling (S¥O¥S) tap (2).
3. Transmission and torque converter filters
Located to the right of the parking brake retraction filters are the transmission and torque converter filters (3). Oil flows from the transmission and torque converter charging pump through the transmission and torque converter filters to the transmission control valves on top of the transmission and to the torque converter lockup clutch valve located on top of the torque converter.
4. Transmission/TC S¥O¥S tap
Transmission and torque converter oil samples can be taken at the Scheduled Oil Sampling (S¥O¥S) tap (4).
5. Transmission/TC filter bypass switch
A transmission and torque converter filter bypass switch (5) is located on the filter base. The bypass switch provides input signals to the Caterpillar Monitoring System or the VIMS which informs the operator if the transmission and torque converter filters are restricted.
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1. Arctic battery cover
Shown is a 775D update truck with the arctic attachment installed. Trucks with the arctic attachment have a second set of batteries located under the battery cover (1).
¥ No precleaners with arctic attachment
To make room for the additional batteries, the air filter housings are installed vertically and there are no precleaners. Two filter elements are installed in the filter housings. The large element is the primary element (2) and the small element is the secondary element (3).
2. Primary element 3. Secondary element
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¥ Steering system tank
Located behind the air filters is the steering system tank.
1. Steering system oil level sight gauge
Check the steering system oil level at the sight gauge (1).
2. Steering system oil filter
The steering system oil filter (2) is located on the side of the steering tank. Steering system oil samples can be taken from the Scheduled Oil Sampling (S¥O¥S) tap (3) located on top of the steering filter.
3. Steering system S¥O¥S tap
4. Case drain oil filter screen fitting 5. Steering tank pressure release button and breather
The steering system uses a pressure compensated piston type pump. Case drain oil from the steering pump returns to the hydraulic tank through a screen that is part of the fitting (4) installed in the side of the steering tank. Before removing the cap 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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1. Brake master cylinders 2. Brake oil makeup tank 3. Brake cylinder breather
4. Brake overstroke switch
Located near the air filters and the steering tank are the front and rear brake cylinders (1) and the brake oil makeup tank (2). Inspect the condition of the breathers (3) for the brake cylinders. Oil should not leak from the breathers. Oil leaking from the breathers is an indication that the oil piston seals in the brake cylinder need replacement. Air flow from the breathers during a brake application is an indication that the brake cylinder air piston seals need replacement. If air is in the system or a loss of oil downstream from the cylinders occurs, the piston in the cylinder will overstroke and cause an indicator rod to extend and open the brake overstroke switch (4). The switch provides an input signal to the Caterpillar Monitoring System or the VIMS which informs the operator of the condition of the service/retarder brake oil circuit. If an overstroke condition occurs, the problem must be repaired and the indicator rod pushed in to end the warning.
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1. Service/retarder brake tanks 2. Service/retarder brake tank drain valve 3. Brake relay valves ¥ Double check valve ¥ Inversion valve
The service and retarder brake air tanks (1) are located behind the brake cylinders and the brake oil makeup tank. Drain condensation from the tanks daily with the drain valve (2). Located above the service and retarder brake air tanks are the brake relay valves (3), a double check valve and the inversion valve.
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¥ 10 hours/daily checks performed in the operator's cab
The remaining 10 Hours or Daily checks are performed in the operator's compartment. They are as follows: - Brakes: Check operation - Indicators and gauges: Test operation - Seat belt: Inspect - Back-up alarm: Test operation - Secondary steering: Test operation The brakes are checked by engaging one of the brake systems 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 for each brake lever or pedal. See the Operation and Maintenance Manual for more information on the remaining tests performed in the cab.
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¥ VIMS service lamp
The blue service lamp (arrow) located on the left side of the cab is part of the attachment Vital Information Management System (VIMS). When the key start switch is turned to the ON position, The VIMS runs through a self test. During the self test the service lamp will flash three times if there are logged events stored in the VIMS main module and once if there are no logged events. During normal operation, the service lamp will turn ON to notify service personnel that the VIMS has an active machine or system event. The service lamp flashes to indicate when an event is considered abusive to the machine.
INSTRUCTOR NOTE: For more detailed information on the VIMS, refer to the Service Manual Module "Vital Information Management System (VIMS)" (Form SENR6059).
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769D/771D/773D/775D UPDATE OFF-HIGHWAY TRUCKS CATERPILLAR MONITORING SYSTEM OR VITAL INFORMATION MANAGEMENT SYSTEM (VIMS)
12
MPH km/h
VIMS DISPLAY MODULES
- GAUGES - MONITORING - WARNINGS - CLOCK SYCHONIZATION - MACHINE ID
3F
SPI LINK
ENGINE TEMP 60 Deg F
- GAUGES - MONITORING - WARNINGS - CLOCK SYCHONIZATION - MACHINE ID - TELEMETRY - PAYLOAD MEASUREMENT - STRUT DIAGNOSTICS
[135]
OK
ID
SERVICE TOOL
CAT DATA LINK ADEM II - EMISSIONS CONTROL - FUEL INJECTION - ETHER INJECTION - FAN CONTROL - ENGINE PRE-LUBE
VIMS MAIN MODULE
INTEGRATED BRAKE CONTROL (IBC) - TRACTION ASSIST - RETARDING - OVERSPEED RETARDING - RETARDING LAMP
EPTC III
- ICM CONTROL - NEUTRAL START - BACKUP ALARM - OVERSPEED PROTECTION - CTS - ENGINE PRE-LUBE - DIRECTIONAL SHIFT MANAGEMENT - AUTOLUBE
INTERFACE MODULES
- TOP GEAR LIMIT - REVERSE NEUTRALIZE - LOAD COUNTER - NEUTRAL COAST INHIBIT - BODY UP GEAR LIMIT - STARTER PROTECTION - BODY HOIST CONTROL - SECONDARY STEERING - SPEED LIMITER
16 OPERATORÕS STATION Caterpillar Monitoring System ¥ Caterpillar Monitoring System is standard
The Caterpillar Monitoring System is the standard monitoring system installed on the D-series update Off-highway Trucks. The Caterpillar Monitoring System is a flexible, modular monitoring system that includes: a message center module, various switches and sensors, an action lamp and action alarm. The "heart" of the system is the message center module where information is received from switches and sensors over the CAT Data Link and processed. The message center module then activates various outputs.
¥ VIMS is possible future option
The Vital Information Management System (VIMS) is being tested as a possible future attachment on the D-series update trucks. If a truck is equipped with the VIMS, the message center control module of the Caterpillar Monitoring System is replaced with the VIMS message center module, a keypad module, a VIMS main module and two interface modules.
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¥ Middle front dash panel
Shown is the middle of the front dash panel. Nine dash indicators, the four-gauge cluster module and the speedometer/tachometer module are shown.
¥ Left dash indicators (top to bottom)
The four dash indicators to the left of the four-gauge cluster module are (from top to bottom):
- Left turn - Body up - Reverse - High Beam
¥ Left Turn ¥ Body Up--Lights when the body is up. Input is from the Body Up switch. ¥ Reverse--Lights when the shift lever switch is in REVERSE. ¥ High Beam
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¥ Right dash indicators (top to bottom) - Right turn
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The five dash indicators to the right of the Speedometer/Tachometer Module are (from top to bottom): ¥ Right Turn
- Action lamp - Secondary steering - Retarder - TCS
¥ Action Lamp--Lights when a Category 2 or Category 3 warning is active. ¥ Secondary Steering--Lights when the secondary steering pump is ON. ¥ Retarder--Lights when the retarder is ENGAGED (Auto or Manual). ¥ TCS--Lights when the Traction Control System (TCS) is ENGAGED.
¥ Four-gauge cluster module: - Engine coolant temperature - Brake oil temperature - System air pressure
The four systems monitored by the Four-Gauge Cluster Module are (top then bottom left to right): ¥ Engine Coolant Temperature--Maximum operating temperature: 107 ¡C (225 ¡F) ¥ Brake Oil Temperature--Maximum operating temperature: 121 ¡C (250 ¡F)
- Fuel level
¥ System Air Pressure--Minimum operating pressure: 483 kPa (70 psi) on trucks with the Caterpillar Monitoring System. 450 kPa (65 psi) on trucks with the VIMS. ¥ Fuel Level--Minimum operating level: 8% on trucks with the Caterpillar Monitoring System. On trucks with the VIMS there are two fuel level warning Categories: - 10%--Category 1 - 5%--Category 2
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¥ Rocker switches (top row):
To the right of the Speedometer/Tachometer Module are several rocker switches. The rocker switches control the following systems:
- Lights - Automatic retarder control - Traction control system test - Operator modes scroll
Top row (from left to right) ¥ Lights ¥ Vacant ¥ ARC--Turns on the Automatic Retarder Control (ARC) system. ¥ TCS Test--Tests the Traction Control System (TCS). Use this switch when turning in a tight circle with the engine at low idle and the transmission in FIRST GEAR. ¥ Caterpillar Monitoring System Operator Scroll--Allows the Operator to scroll through the Operator Modes in the Message Center Module display window.
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¥ Rocker switches (bottom row): - Throttle backup/ throttle lock - Ether starting aid - Air conditioning - Body up sound reduction - Secondary steering and brake retraction
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Bottom row (from left to right) ¥ Throttle Backup/Throttle Lock: (customer installed option) - Throttle Backup--Raises the engine speed to 1300 rpm if the throttle sensor signal is invalid. - Throttle Lock--If the transmission is in NEUTRAL and the parking brake is ENGAGED, the throttle lock will hold any current engine rpm selected by the operator. If any service/retarder brake is ENGAGED, the engine rpm will return to LOW IDLE. After a brake application, the throttle lock must be turned OFF to reset the system before the throttle lock function will work again. ¥ Ether Starting Aid--Allows the Operator to manually inject ether if the engine oil temperature is below 10 ¡C (50 ¡F) and engine speed is below 1200 rpm (customer installed option). ¥ Air Conditioning ¥ Body Up Sound Reduction--Reduces engine HIGH IDLE to 1800 rpm when the body is raised. ¥ Secondary Steering and Brake Retraction--Normally when this switch is depressed, the steering system receives secondary steering oil flow and brake retraction oil flows to tank. When the brake retraction diverter (towing) valve spool is shifted, this switch will also release the parking brakes (see Slide No. 71).
NOTE: The Secondary Steering and Brake Retraction switch can also be used to provide hoist pilot oil for lowering the body on trucks with a dead engine (see Slide No. 62).
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19 ¥ Message center module
To the right of the rocker switches is the Message Center Module. The Message Center Module contains ten alert indicators and a message display window.
¥ Alert indicators (top row):
The alert indicators on the message center module represent the following systems:
- Engine oil pressure - Parking brake ON or brake master cylinder overstroke - Torque converter oil temperature or brake oil temperature - Battery charging - Engine maintenance required
Top row (from left to right) ¥ Engine Oil Pressure--Minimum operating pressures: - Low Idle - 44 kPa (6.4 psi) - High Idle - 250 kPa (36 psi) ¥ Parking Brake ON or Brake Master Cylinder Overstroke ¥ Torque Converter Oil Temperature or Brake Oil Temperature-Maximum operating temperature: 121 ¡C (250 ¡F) ¥ Battery Charging--Minimum voltage on Message Center pin 1: 23 Volts. Minimum "R" terminal frequency/voltage: 95 Hz/12.4 to 14.75 DC volts. ¥ Engine Maintenance Required--Steering pressure low Air filter restriction Engine coolant flow low
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¥ Alert indicators (bottom row): - Air filter restriction - Steering pressure low - Transmission oil filter restricted - Engine coolant flow low - Check engine
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Bottom row (from left to right) ¥ Air Filter Restriction--Maximum allowable restriction: 7.5 kPa (30 inches of water) ¥ Steering Pressure Low ¥ Transmission/Torque Converter Oil Filter Restricted--Maximum differential pressure: 250 kPa (36 psi) ¥ Engine Coolant Flow Low ¥ Check Engine--Lights only when there are active engine fault codes
¥ Message display window
The message display window has a row of six digits, a decimal point between certain digits, six text symbols (units of measure), a x10 symbol and a service meter symbol that show machine system conditions and other service and setup information. The type of information shown on the screen depends on the message center operating mode.
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1. CAT Data Link connector
Shown is the fuse panel located behind the operator's seat. A laptop computer with the Electronic Technician (ET) software installed can be connected to the CAT Data Link connector (1) to obtain diagnostic information and perform programming functions on all of the electronic controls.
2. 12 Volt/5 amp power port
A 12 Volt/5 amp power port (2) provides an additional power supply for a laptop computer.
3. TPMS/VIMS diagnostic connector
A laptop computer with the Truck Production Management System (TPMS) or VIMS software installed can be connected to the diagnostic connector (3) to obtain diagnostic and production information from the TPMS or VIMS Electronic Control.
4. Caterpillar Monitoring System message center service switches
Two Service Switches (4) and (5) are used to access the Caterpillar Monitoring System Message Center for stored diagnostic information. The switches are labeled with an "S" for SET or SCROLL and a "C" for CLEAR. The Diagnostic Mode of the Message Center is changed by depressing and holding both service switches "S" and "C". When the desired mode is shown on the display, the switches can be released. By following the instructions in the Caterpillar Monitoring System Service Manual, the serviceman can program or diagnose faults in all electronic controls on the CAT Data Link.
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OPERATOR MODES INPUTS SERVICE METER MODE ODOMETER MODE
41.4
DIAGNOSTIC SCROLLING MODE
- ENGINE SPEED/TIMING SENSOR - ALTERNATOR "R" TERMINAL - ENGINE OIL PRESSURE
MILES or KM
- TRANSMISSION OUTPUT SPEED SENSOR
170
DIGITAL TACHOMETER MODE RESETTABLE LOAD COUNTER MODE
SERV CODE
RPM
- ENGINE SPEED/TIMING SENSOR
700 L
- BODY UP SWITCH (AFTER 10 SECONDS ACTIVATION) Use "C" Service Switch to Clear
74 030
SERV CODE
271 F05
MID
SERV CODE
CID FMI
21 ¥ Message center module display window
The Caterpillar Monitoring System has eight different possible modes of operation. Each mode provides important information regarding the condition of the machine and setup of the monitoring system. On the message center module display window, each mode is shown as a number. The mode of operation is changed using either the Service Switches located on the fuse panel behind the Operator or the Operator Mode Scroll Switch located on the dashboard. Only some modes are accessible to the Operator by using the dashboard-mounted rocker switch in Mode 0. After the Caterpillar Monitoring System first powers up, the message center display window will be in Mode 0. In Mode 0, the display window six-digit readout shows various machine system conditions to the Operator. The digital readout normally shows the service meter. Using the Operator Mode Scroll Switch, the Operator may scroll through the different Operator modes. As the display scrolls, it will show the following information:
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¥ Operator modes: - Service meter mode - Odometer mode - Digital tachometer mode - Resettable load counter mode - Diagnostic scrolling mode
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¥ Service Meter Mode: The message center module keeps track of the engine's total number of operating hours. When in service meter mode, the six digit readout shows total machine operating hours. The service meter symbol is ON to indicate the display is functioning as a service meter. The operating hours will only increase when there are input signals from the engine speed timing sensor, the alternator "R" terminal and the engine oil pressure sensor. If there is an Active Fault, SERV CODE will be displayed in the window. ¥ Odometer Mode: In this mode, the six-digit readout displays the total distance the machine has traveled. The units indicator will show MILES or KM, depending on the units of measure setting. The distance traveled will only increase when there is an input signal from the transmission output speed sensor. ¥ Digital Tachometer Mode: This mode displays the engine speed in revolutions per minute on the six-digit display. The units indicator shows RPM. The engine speed/timing sensor provides the input signal to the message center module. ¥ Resettable Load Counter Mode: Displays the number of loads since last re-set by the operator. The number of loads is calculated as equal to the number of times the body has been raised for more than ten seconds. The body up switch provides the input signals to the message center module. The load count can be cleared by depressing the "C" Service Switch located behind the Operator's seat. ¥ Diagnostic Scrolling Mode: Using this mode, service personnel or the operator can view the faults the message center has detected. Faults CANNOT be placed on hold or cleared in this mode. "SERV CODE" will only be displayed if the fault is ACTIVE. Fault Codes consist of two parts:
¥ Diagnostic codes in serviceman's handouts
¥ MID
- Module Identification. 030--Monitor, 036--ADEM II, 027--EPTC III, 116--ARC/TCS
¥ CID, FMI
- Component Identification and Failure Modifier
Refer to the Serviceman's Handouts for a listing of the Diagnostic Codes used on the D-series update Off-highway Trucks.
NOTE: During engine cranking, if the Caterpillar Pre-Lubrication System is installed, a "P" will appear on the display during pre-lubrication. During engine cranking, if the ether starting aid is installed, an "E" will appear on the display during ether injection.
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SERVICE MODES HARNESS CODE MODE
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NUMERIC READOUT MODE
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SERV CODE
59
USE "S" SERVICE SWITCH TO SCROLL GAUGES
°C
°C
95
GA-1 (engine coolant) SERVICE MODE
kPa
88
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715
GA-2 (brake oil)
030
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SERV CODE
MID LOG MODE
UNITS MODE PERMANENT LOAD COUNT MODE DIAGNOSTIC AND PROGRAMMING MODE
LOG
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-6-7-
KM
US L
271 F05 CID
SERV CODE
GA-4 (fuel) USE "S" SERVICE SWITCH TO SCROLL FAULTS USE "C" SERVICE SWITCH TO CLEAR FAULTS
FMI
ALL GAUGES AND INDICATORS DISPLAY EXTREME CONDITIONS RECORDED
MILES
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75
GA-3 (system air)
USE "C" SERVICE SWITCH TO CLEAR
USE "C" SERVICE SWITCH TO CHANGE UNITS
SI
1057 n
n
3 F
3FL
USE "S" SERVICE SWITCH TO SCROLL SUB-MODES
22 ¥ Service modes: - Harness code mode 1 - Numeric readout mode 2 - Service mode 3 - Log mode 4 - Units mode 5 - Permanent load count mode 6 - Diagnostic and programming mode 7
The Service Technician can use the message display to check other machine condition information by selecting the different modes available. Depress both Service Switches behind the Operator's seat to Scroll through the Modes. Release the switches to enter a Mode when its number is displayed. The seven Service Modes are described below. ¥ Harness Code Mode 1: This mode shows the machine model that the monitoring system is installed on. 769D through 777D pre-update Off-highway Trucks are all "34." D-series update truck harness codes are: 769D--"62"
771D--"61"
773D--"60"
775D--"59"
¥ Numeric Readout Mode 2: This mode assists service personnel with troubleshooting sensor inputs. Numeric readout mode more accurately shows the same information as that shown on the gauges. The digital readout will display one gauge value at a time. To scroll through the four gauges, depress the "S" Service Switch and release the switch when the desired gauge number is displayed.
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¥ SERV CODE on for active faults
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¥ Service Mode 3: The message center module detects faults that occur with sensor/sender inputs and message center module outputs. The message center will then record the fault and turn on the "SERV CODE" indicator. If the fault goes away, the "SERV CODE" indicator is turned off. The fault code remains stored for future reference. This mode helps service personnel see and trouble shoot faults that the message center module has detected. Faults from other machine systems that are attached to the Data Link are also shown in this mode.
¥ Action alarm sounds when fault is displayed
When a fault is displayed in the window, the Action Alarm will sound when the component or circuit changes state. For example, if the display shows the fault code for the torque converter temperature sensor and the technician unplugs and then plugs in the connector to the torque converter temperature sensor, the Action Alarm will sound if the Message Center Module detects a change from an OPEN to a completed circuit.
¥ Use "S" service switch to scroll faults
Use the "S" Service Switch to scroll through logged faults. Use the "C" Service Switch to clear logged faults that have been repaired.
¥ Use "C" service switch to clear faults
¥ Log mode indicates extreme conditions
¥ Log Mode 4: Log mode is a management and maintenance tool, useful for tracking machine history. The message center module records the extreme value for each machine condition monitored. When in this mode, each gauge in the four-gauge cluster will display its highest or lowest recorded condition and the speedometer and tachometer will display their highest recorded values. Alert Indicators will also light when an abnormal condition has existed. Use the "C" Service Switch to clear the logged values. Mode 4 must also be exited before the logged values will be cleared from memory. ¥ Units Mode 5: This mode is used to toggle the Ground Speed display (MPH/km/h) between U.S. and SI (metric) units of measure. Use the "C" Service Switch to change the units of measure. ¥ Permanent Load Count Mode 6: Displays the total number of loads accumulated since the machine was put into production. The number of loads is calculated as equal to the number of times the body has been raised for more than 10 seconds. This Mode is not resettable.
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¥ Diagnostic and Programming Mode 7: The Caterpillar Monitoring System display for Mode 7 has been expanded to include several sub-modes to extend the diagnostic capabilities. After entering Mode 7, use the "S" service switch to scroll through the sub-modes. The operator scroll switch and the "C" service switch can also be used in some of the sub-modes. The sub-modes in Mode 7 are as follows: 7.1 Shift Monitoring Mode--displays the position of the shift lever sensor on the left of the display and the position of the transmission gear switch on the right of the display. The D6 digit will display an "L" when the lockup clutch is ENGAGED. n 1 r 3 F --D1 D2 7.2
L -D6
<--digital position on display
1 8 --D3 D4
3 -D5
4 -D6
<--TOS = 1834 <--digital position on display
Torque Converter Output Speed (COS) Display Mode--displays the rpm of the COS sensor (if equipped). C --D1 D2
7.4
r F -D5
<--cane n, actual gear n, lockup clutch OFF <--cane 1R, actual gear 1R, lockup clutch OFF <--cane 3F, actual gear 3F, lockup clutch ENGAGED
Transmission Output Speed (TOS) Display Mode--displays the rpm of the TOS sensor. T --D1 D2
7.3
n 1 3 --D3 D4
1 8 --D3 D4
3 -D5
4 -D6
<--COS = 1834 <--digital position on display
Engine Output Speed (EOS) Display Mode--displays the rpm of the EOS sensor. E --D1 D2
1 8 --D3 D4
3 -D5
4 -D6
<--EOS = 1834 <--digital position on display
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7.5
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Hoist Display Mode--displays the hoist lever sensor INPUT to the Transmission and Chassis Control or the hoist lever OUTPUT from the Transmission and Chassis Control. The input and output can be different depending on the hoist lever strategy. For example, if a machine is started with the hoist lever in FLOAT, the hoist strategy will keep the body in HOLD until the lever is cycled from FLOAT to HOLD and then back to FLOAT. Therefore, the input can be FLOAT and the output will be HOLD. H H H H -D1
L L L L -D2
4 8 1 0 --D3 D4
0 0 0 0 -D5
H L R F -D6
<--hoist lever in HOLD <--hoist lever in 40% LOWER <--hoist lever in 80% RAISE <--hoist lever in 100% FLOAT <--digital position on display
Depress the Operator Scroll Switch and the above display changes to show the hoist OUTPUT. The "L" changes to an "O" and the state of the hoist system is displayed in the same format. H 0 --D1 D2
7.6
--D3 D4
0 -D5
S -D6
<--hoist output in SNUB <--digital position on display
Transmission Gear Switch Input Mode--displays the transmission gear switch input signals to the Transmission and Chassis Control. Transmission gear switch inputs correspond to pins 29, 30, 31, 32, 33 and 35 in the J1 connector of the Transmission and Chassis Control. If the particular input is grounded, a "0" will be displayed. If the input is not grounded (OPEN), a "1" will be displayed. A normal transmission gear position will have two of the five gear wires grounded along with the ground verify signal (pin 35). Pin 35 should always be grounded and a "0" should always be displayed in the D1 position of the display. Therefore, a correctly functioning Transmission Gear Switch and Harness should always have three 0's and three 1's for each gear position. 0 0 0 0 0 0 0 0 0 -D1 35
0 0 0 0 1 1 1 1 1 -D2 33
0 1 1 1 0 0 0 1 1 -D3 32
1 0 1 1 0 1 1 0 0 -D4 31
1 1 0 1 1 0 1 0 1 -D5 30
1 1 1 0 1 1 0 1 0 -D6 29
<--pins grounded in NEUTRAL <--pins grounded in REVERSE <--pins grounded in 1st <--pins grounded in 2nd <--pins grounded in 3rd <--pins grounded in 4th <--pins grounded in 5th <--pins grounded in 6th <--pins grounded in 7th <--digital position on display <--pin number in the J1 connector
32 & 33 31 & 33 30 & 33 29 & 33 31 & 32 30 & 32 29 & 32 30 & 31 29 & 31
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7.7
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Economy Shift Program Mode--displays whether the Economy Shift feature is ON or OFF. The Operator can select between faster cycle times or better fuel economy. Turning this feature ON or OFF changes the torque map used by the engine control and the shift points used by the transmission control. ON is ECONOMY mode. OFF is FULL POWER mode. When the Economy Shift feature is ON, full power is still used in 1st and 2nd Gear. The Economy torque map is only used in gears THREE and up. Use the "C" Service Switch to turn this feature ON or OFF..
--D1 D2
O --D3 D4
F -D5
F -D6
<--setting at OFF <--digital position on display
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23
¥ Electronic Technician (ET)
Shown is the 7X1700 Communication Adapter and a laptop computer with the Electronic Technician (ET) diagnostic software installed. The communication adapter is connected to the CAT Data Link diagnostic connector located on the fuse panel.
¥ ET must be used with new MAC14 controls
The new electronic controls [Transmission and Chassis control (EPTC III), Integrated Brake Control (IBC), ARC and TCS] used on the D-series update trucks no longer have diagnostic windows to access diagnostic information. The new controls are called Multiple Application Controls with 14 output capability (MAC14). In order to perform diagnostic and programming functions in the new MAC14 controls, the service technician must use a laptop computer with ET.
¥ ET version 2.0 required for IBC
ET version 2.0 or greater must be used to communicate with the Integrated Brake Control (IBC).
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1
2
24
Vital Information Management System (VIMS) ¥ VIMS possible future attachment
The Vital Information Management System (VIMS) is being tested as a possible future attachment on the D-series update trucks. If a truck is equipped with the VIMS, the message center control module of the Caterpillar Monitoring System is replaced with the VIMS message center module (1) and the keypad module (2).
1. Message center module: - Alert indicator - Universal gauge - Message display window
The message center module consists of an alert indicator, a universal gauge and a message display window. The alert indicator flashes when a Category 1 Warning is present. The universal gauge displays the status of the sensor selected for viewing by depressing the GAUGE key on the keypad. The message display window shows various types of text information to the operator.
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2. Keypad module
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The keypad module allows the operator or a service technician to interact with the VIMS. Some of the functions that can be performed by the keypad are: - Calibrate Payload Monitor
PAYCAL
729225
- Payload Resettable Totals
TOT
868
- Reset Displayed Data
RESET
73738
- Display Self Test
TEST
8378
- Reset Service Light
SVCLIT
782548
- Show Acknowledged Events
EACK
3225
- Show Event Statistics
ESTAT
37828
- Show Event List
ELIST
35478
- Start Event Recorder
EREC
3732
- Start/Stop Data Logger
DLOG
3564
- Reset Data Logger
DLRES
35737
- Odometer Set/Reset (requires VIMS PC connection)
ODO
636
- Machine Status
MSTAT
67828
- Change Language
LA
52
- Change Units
UN
86
- Change Backlight
BLT
258
- Change Display Contrast (requires Updated Message Center)
CON
266
OK Key--Used to complete keypad entries and to acknowledge events. Acknowledging an event will remove the event from the display temporarily. Severe events cannot be acknowledged. GAUGE key--Displays parameters monitored by VIMS. Depressing the arrow keys will scroll through the parameters. Entering the parameter number and the GAUGE key selects that parameter. F1 Key--Provides additional information on the current event being displayed. For SYSTEM events, the MID, CID, FMI is displayed. For MACHINE events, the current parameter value is displayed (temperature, pressure, rpm).
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SERVICE KEYSWITCH
VIMS RS-232 PORT
SPEEDOMETER/ TACHOMETER MODULE
GAUGE CLUSTER MODULE
SERVICE LAMP
12
MAIN MODULE
KEYPAD MODULE
3F
VIMS SERVICE TOOL AND SOFTWARE
ELECTRONIC TECHNICIAN/ECAP DISPLAY DATA LINK
VIMS
MPH km/h
MESSAGE CENTER MODULE
VIMS INTERFACE MODULE
VIMS INTERFACE MODULE
KEYPAD DATA LINK CAT DATA LINK
ADEM II CONTROL ACTION ALARM
ACTION LAMP CAT DATA LINK SENSORS
SENSORS SENSORS
VITAL INFORMATION MANAGEMENT SYSTEM (VIMS) INTEGRATED BRAKE CONTROL (ARC) (TCS)
TRANSMISSION AND CHASSIS CONTROL
25 ¥ VIMS
The VIMS operates very similar to the Caterpillar Monitoring System. The VIMS uses two interface modules to receive input signals from many sensors located around the machine. The VIMS also communicates with other electronic controls on the machine. The VIMS provides the operator and the service technician with a complete look at the current and past conditions of all the systems on the truck.
¥ TPMS is part of VIMS
If the truck is equipped with the VIMS, the TPMS is an integral part of the VIMS. Access to the TPMS information is provided through the VIMS message center and keypad modules and a laptop computer with the VIMS PC software installed.
¥ ET required for programming and diagnostics
While VIMS monitors all of the systems on the truck, ET is used for programming, running diagnostic tests and retrieving logged information from the engine, transmission and chassis, ARC and TCS electronic controls.
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4 1
2 3 5
26
1. VIMS main module 2. VIMS interface module #1 3. VIMS interface module #2 4. Transmission and chassis control 5. ARC and TCS control
Located in the compartment at the back of the cab is the VIMS Main Module (1), the VIMS Interface Module #1 (2) and the VIMS Interface Module #2 (3). These components make up the heart of the VIMS. Also in this location is the transmission and chassis control (4) and the ARC and TCS control (5). All of these electronic controls, along with the engine control, communicate with each other on the CAT Data Link. All of the information from these controls can be accessed through the VIMS message center or a laptop computer with ET or VIMS PC software.
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27
¥ VIMS connector
Shown is a laptop computer with the VIMS PC diagnostic software installed. The laptop computer is connected to the VIMS diagnostic connector. This connector is the same one used for TPMS on trucks without the VIMS. Some of the operations that can be performed with a laptop computer with VIMS PC installed are: - View real time data (similar to the status menu of ET) - View payload data - Start and stop a data logger - Calibrate the payload system - Upload source and configuration files (similar to flash programming with ET) - Assign serial and equipment numbers - Reset onboard date, time and hour meter - Download event list, data logger, event recorder, payload data, trend data, cumulative data and histogram data
INSTRUCTOR NOTE: For more detailed information on the VIMS, refer to the Service Manual Module "Vital Information Management System (VIMS)" (Form SENR6059).
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1
4
2
3
28
POWER TRAIN Power Train Components ¥ Torque converter: - Provides a fluid coupling - Multiplies torque - Provides direct drive operation
1. Lockup clutch control valve 2. Outlet pressure relief valve 3. Transmission and torque converter pump 4. Transmission and torque converter suction screen
The first component in the power train is the torque converter. The torque converter provides a fluid coupling that permits the engine to continue running with the truck stopped. In converter drive, the torque converter multiplies torque to the transmission. At higher ground speeds, a lockup clutch engages to provide direct drive. The NEUTRAL and REVERSE ranges are converter drive only. FIRST SPEED is converter drive at low ground speed and direct drive at high ground speed. SECOND through SEVENTH SPEEDS are direct drive only. The torque converter goes to converter drive between each shift (during clutch engagement) to provide smooth shifts. Mounted on the torque converter case are the lockup clutch control valve (1), the outlet pressure relief valve (2), the transmission and torque converter pump (3) and the transmission and torque converter suction screen (4).
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2 3
1
29
¥ 775D update truck 1. Transfer gears 2. Transmission
Shown are some of the power train components in a 775D update truck. Power flows from the torque converter through a drive shaft to the transfer gears (1). The transfer gears are splined to the transmission.
3. Differential
The transmission (2) is located between the transfer gears and the differential (3). The transmission is electronically controlled and hydraulically operated like all other ICM (Individual Clutch Modulation) transmissions in Caterpillar rigid frame trucks.
¥ Transmission is power shift planetary design
The transmission is a power shift planetary design which contains seven hydraulically engaged clutches. The transmission provides seven FORWARD speeds and one REVERSE speed. The differential is located in the rear axle housing behind the transmission. Power from the transmission flows through the differential and is divided equally to the final drives in the rear wheels. The final drives are single reduction planetaries.
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1
2
4
5 3
30
Power Train Hydraulic System ¥ Torque converter housing is oil sump ¥ Two section pump: 1. Transmission scavenge 2. Transmission and torque converter charging 3. Transmission scavenge oil return baffle cover 4. Suction screen cover 5. Transmission and torque converter charging filters
¥ Charging oil flows in two directions: - To torque converter lockup clutch valve - To transmission control valves
The torque converter housing is the oil sump for the transmission and torque converter oil supply. A two section transmission and torque converter pump is located at the rear of the torque converter. The rear section is the transmission scavenge section (1) of the pump and the front section is the transmission and torque converter charging section (2) of the pump. The transmission scavenge section pulls oil through the magnetic screen located at the bottom of the transmission case (see next slide). The scavenged oil from the transmission is transferred into the torque converter case through a baffle (diffuser) located behind the cover (3). The transmission and torque converter charging section of the pump pulls oil from the torque converter case through the suction screen located behind the cover (4). Oil flows from the charging section to the transmission and torque converter charging filters (5). Charging oil flows in two directions from the filters: - Charging oil flows to the torque converter lockup valve located on top of the torque converter. - Charging oil also flows to the transmission control valves located on top of the transmission.
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31
¥ Transmission magnetic scavenge screen (arrow)
Shown is the transmission scavenge screen (arrow) and the magnet assembly that fits inside the screen. The screen is located in the bottom of the transmission case. The screen should always be checked for debris if a problem with the transmission is suspected. Oil is scavenged from the transmission by the rear section of the transmission and torque converter pump (see previous slide).
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3 2
1
32
1. Transmission and torque converter filters 2. Transmission/TC S¥O¥S tap 3. Transmission/TC filter bypass switch
Shown are the transmission and torque converter charging filters (1). Transmission and torque converter oil samples can be taken at the Scheduled Oil Sampling (S¥O¥S) tap (2). A transmission and torque converter filter bypass switch (3) is located on the filter base. The bypass switch provides input signals to the Caterpillar Monitoring System or the VIMS which informs the operator if the transmission and torque converter filters are restricted.
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3
2
1 4
33
1. Torque converter lockup valve 2. Lockup valve supply port 3. Lockup solenoid
The transmission and torque converter charging pump supplies oil to the torque converter lockup valve (1) through the inlet port (2). When the lockup solenoid (3) is energized by the transmission and chassis control, the lockup valve supplies oil to ENGAGE the lockup clutch in the torque converter.
4. Torque converter lockup clutch pressure tap
Torque converter lockup clutch pressure can be measured at the tap (4). Torque converter lockup clutch pressures are as follows: 769D/771D--Pressure will increase to 2065 ± 100 kPa (300 ± 15 psi) for 0.15 seconds, then decrease and hold at 1720 ± 100 kPa (250 ± 15 psi). 773D/775D--Pressure will increase to 2410 ± 100 kPa (350 ± 15 psi) for 0.15 seconds, then decrease and hold at 2065 ± 100 kPa (300 ± 15 psi).
¥ Lockup clutch pressure test
To check the lockup clutch pressure the drive shaft must be disconnected at the torque converter or the rear axles must be removed. Move the shift lever to first forward and raise the engine speed to HIGH IDLE. The lockup clutch will engage at approximately 6.4 km/h (4 mph). An 8T5200 Signal Generator/Counter can also be used to shift the transmission.
¥ Lockup clutch pressure NOT adjustable
The lockup clutch pressure is not adjustable. If the lockup clutch pressure is not correct, verify that the lockup valve is operating correctly. Check for loose or sticking components or debris in the valve. If the lockup valve is operating correctly and the lockup clutch pressure is incorrect, a new flash file may be required.
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TORQUE CONVERTER LOCKUP VALVE
LOCKUP SOLENOID
DRAIN
PIN
LOCKUP PRESSURE
PUMP SUPPLY
CONTROL SPOOL
34 ¥ Lockup clutch control valve operation
The transmission and chassis control provides a Pulse Width Modulated (PWM) signal to the lockup solenoid to control the lockup pressure. When the lockup solenoid is energized, the pin moves to the right and pushes against the ball. The ball blocks the pump supply oil from flowing to drain. Pressure increases in the chamber to the left of the control spool and moves the spool to the right. When the control spool moves to the right, pump supply oil flows to the lockup clutch. The transmission and chassis control opens and closes the ball drain port as needed to maintain the correct lockup clutch pressure.
¥ ECPC valve
The lockup clutch valve is often referred to as the Electronic Clutch Pressure Control (ECPC) valve because it can control clutch pressure electronically. A similar valve is used on Track-type Tractors and Wheel Loaders.
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6
2
3 7
5 1
4
35
1. Transmission charging oil inlet port 2. Shift solenoids 3. Torque converter charging oil supply hose 4. Torque converter inlet relief valve
Shown is the Individual Clutch Modulation (ICM) transmission hydraulic control valve. Oil flows from the transmission and torque converter charging filters through the inlet port (1) to the transmission hydraulic control valve and the shift solenoids (2). The charging oil is used to shift the transmission and fill the clutches. Some of the charging oil drops to the bottom of the housing to be scavenged, but most of the oil flows to the torque converter through the outlet hose (3) to provide charging oil for the torque converter. The torque converter inlet relief valve (4) limits the maximum pressure to the torque converter. The setting of the torque converter inlet relief valve is 930 kPa (135 psi).
5. Transmission charging pressure tap
The transmission charging pressure relief valve is part of the transmission hydraulic control valve. The relief valve limits the maximum pressure in the transmission charging circuit. Transmission charging pressure can be measured at the tap (5). Transmission pressure should be a minimum of 2480 kPa (360 psi) at LOW IDLE and a maximum of 3200 kPa (465 psi) at HIGH IDLE.
6. Transmission clutch pressure taps
Transmission clutch pressures are measured at the pressure taps (6).
7. Transmission lube inlet port
Lubrication and cooling oil from the the transmission and torque converter oil cooler enters the transmission through inlet port (7).
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36
¥ Transmission lube tap (arrow)
Shown is the left side of the transmission. Transmission lube pressure can be measured at the tap (arrow) located below the lubrication supply hose. Lube pressure should be greater than 3.5 kPa (0.5 psi) at LOW IDLE and between 140 to 205 kPa (20 to 30 psi) at HIGH IDLE.
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ICM HYDRAULIC SYSTEM DOWNSHIFT PRESSURE DOWNSHIFT SOLENOID
UPSHIFT PRESSURE
A
UPSHIFT SOLENOID ROTARY ACTUATOR
CHARGING FILTERS
E
PUMP PRESSURE CHARGING PUMP
B
PRIORITY REDUCTION VALVE
NEUTRALIZER VALVE
PILOT OIL PRESSURE LOCKUP VALVE
F
ROTARY SELECTOR SPOOL
C
SCAVENGE PUMP
G
TRANSMISSION CASE
TORQUE CONVERTER
D
RELIEF VALVE
H
TORQUE CONVERTER INLET RELIEF VALVE
SELECTOR VALVE GROUP OIL COOLER
LUBE PRESSURE
PRESSURE CONTROL GROUP
TO TRANSMISSION LUBE
37 ¥ ICM transmission hydraulic control valve
¥ Priority reduction valve ¥ Neutralizer valve
¥ Rotary actuator ¥ Rotary selector spool
¥ Torque converter inlet relief valve
Shown is a sectional view of the ICM transmission hydraulic control valve group. Pump supply oil flows to the shift solenoids, the priority reduction valve, the relief valve and the pressure control group. Pump supply oil also flows to the lockup valve. The relief valve controls the maximum charging pressure in the system. The priority reduction valve reduces transmission relief pressure to be used as pilot oil. Pilot oil flows through the neutralizer valve to the rotary selector spool. The neutralizer valve prevents the clutches from filling with oil if the engine is started with the transmission in gear. The neutralizer valve will only allow pilot oil to flow to the rotary selector spool if it is in NEUTRAL. The rotary actuator is connected to the rotary selector spool. If a shift solenoid is energized, pump supply oil flows to the rotary actuator and rotates the rotary selector spool. The rotary selector spool directs pilot oil to one or two valve stations and allows the clutches to fill with oil. The valve stations control the modulation of clutch engagement and dis-engagement. The torque converter inlet relief valve limits the maximum pressure to the torque converter.
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1
5 3
2 4
38
1. Torque converter charging oil inlet port
Charging oil flows from the transmission and enters the torque converter through inlet port (1). The torque converter charging oil enters the torque converter and provides a fluid coupling.
2. Torque converter outlet relief valve
The torque converter charging oil then either drops to the bottom of the housing or flows through the torque converter outlet relief valve (2). The outlet relief valve limits the pressure inside the torque converter. The outlet relief pressure can be measured at the tap (3) on the outlet relief valve. The outlet relief pressure should be between 205 and 550 kPa (30 and 80 psi) at Stall Speed. Stall Speed should be between 1760 and 1890 rpm.
3. Outlet relief valve pressure tap
4. Torque converter outlet port to oil cooler
All the oil from the torque converter outlet relief valve flows from port (4) through the transmission and torque converter oil cooler located on the right side of the engine. Oil flows from the oil cooler back to the transmission for lubrication. Transmission lube oil flows through the transfer gears and the transmission to cool and lubricate the internal components.
5. Torque converter outlet temperature sensor
A torque converter outlet temperature sensor (5) provides an input signal to the Caterpillar Monitoring System or the VIMS which informs the operator of the torque converter outlet temperature.
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TRANSMISSION AND TORQUE CONVERTER HYDRAULIC SYSTEM MAGNETIC SCAVENGE SCREEN
TORQUE CONVERTER LOCKUP CLUTCH SUPPLY
TORQUE CONVERTER INLET
LOCKUP VALVE
SUCTION SCREEN
RETURN BAFFLE
SHIFT SOLENOIDS
TRANSMISSION AND TORQUE CONVERTER CHARGING FILTERS
TRANSMISSION AND TORQUE CONVERTER OIL COOLER
TORQUE CONVERTER OUTLET
FROM TRANSMISSION MAGNETIC SCAVENGE SCREEN TO TRANSMISSION AND TORQUE CONVERTER CHARGING FILTERS
39 ¥ Transmission and torque converter hydraulic system ¥ Two section pump: - Transmission scavenge - Transmission and torque converter charging
Shown is the transmission and torque converter hydraulic system. A two section transmission and torque converter pump is located at the rear of the torque converter. The rear section is the transmission scavenge section of the pump and the front section is the transmission and torque converter charging section of the pump. The transmission scavenge section pulls oil through the magnetic screen located at the bottom of the transmission case. The scavenged oil from the transmission is transferred into the torque converter case through a baffle (diffuser).
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¥ Transmission and torque converter charging section
- 54 -
The transmission and torque converter charging section of the pump pulls oil from the torque converter case through the suction screen. Oil flows from the charging section to the transmission and torque converter charging filters. Charging oil flows in two directions from the filters: - Charging oil flows to the torque converter lockup valve located on top of the torque converter. - Charging oil also flows to the transmission control valves located on top of the transmission.
¥ Torque converter lockup clutch supply oil
The charging oil that flows to the torque converter lockup valve is blocked from the lockup clutch until the lockup valve solenoid is energized by the transmission and chassis control. When the lockup valve solenoid is energized, the lockup valve supplies oil to ENGAGE the lockup clutch in the torque converter.
¥ Transmission charging oil
The charging oil that flows to the transmission hydraulic control valve also supplies the shift solenoids. The charging oil is used to shift the transmission and fill the clutches. Some of the charging oil drops to the bottom of the housing to be scavenged, but most of the oil flows to the torque converter to provide charging oil for the torque converter.
¥ Torque converter charging oil
The torque converter charging oil enters the torque converter and provides a fluid coupling. Charging oil then either drops to the bottom of the housing or flows through the torque converter outlet relief valve. The outlet relief valve limits the pressure inside the torque converter.
¥ Transmission lube
The oil from the torque converter outlet relief valve flows through the transmission and torque converter oil cooler located on the right side of the engine. Oil flows from the oil cooler back to the transmission for lubrication. Transmission lube oil flows through the transfer gears and the transmission to cool and lubricate the internal components.
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40 Transmission and Chassis Control (EPTC III) ¥ Transmission and chassis control (arrow)
The transmission and chassis control (arrow) is located in the compartment at the rear of the cab. The transmission control used in the D-series pre-update trucks is referred to as the second generation Electronic Programmable Transmission Control (EPTC II).
¥ Transmission and chassis control called EPTC III
The transmission control used in the D-series update trucks performs the transmission control functions plus some other machine functions (hoist and secondary steering control). Because of the added functionality of the control, it is now referred to as the transmission and chassis control. But, to keep written material to a minimum, we will often refer to this control as the third generation Electronic Programmable Transmission Control or (EPTC III).
¥ MAC14 style control
The new control is a MAC14 style electronic control, which means that it is a Multiple Application Control capable of 14 outputs (MAC14). The MAC14 does not have a diagnostic window like EPTC II. Diagnostic and programming functions must all be done with an Electronic Control Analyzer Programmer (ECAP) or a laptop computer with the Electronic Technician (ET) software installed. ET is the tool of choice because the MAC14's can be reprogrammed with a "flash" file using the Winflash application of ET. ECAP cannot upload "flash" files.
- No diagnostic window - Diagnostics and programming requires ECAP or ET
¥ MAC14 looks like ADEM II
MAC14's look like the second generation Advanced Diesel Engine Management (ADEM II) electronic control with two 40-pin connectors, but MAC14's do not have fittings for cooling fluid. Also, there is no access plate for a personality module.
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TRANSMISSION AND CHASSIS CONTROL ELECTRICAL SYSTEM
INPUT COMPONENTS
OUTPUT COMPONENTS CAT DATA LINK
SHIFT LEVER POSITION SENSOR
ELECTRONIC SERVICE TOOL ENGINE CONTROL
TRANSMISSION GEAR SWITCH
ARC AND TCS CONTROL
TRANSMISSION OUTPUT SPEED SENSOR °C kPaMiles KM RPM Liter SERV CODE X10
MESSAGE CENTER MODULE
. ..
CONVERTER OUTPUT SPEED SENSOR
UPSHIFT SOLENOID
ENGINE OUTPUT SPEED SENSOR DOWNSHIFT SOLENOID
SERVICE/RETARDER BRAKE PRESSURE SWITCH
LOCKUP SOLENOID
PARKING/SECONDARY BRAKE PRESSURE SWITCH BODY UP SWITCH
BACK-UP ALARM
STARTER RELAY AUTO LUBE SOLENOID
KEY START SWITCH SECONDARY STEERING RELAY LOW STEERING PRESSURE SENSOR HOIST RAISE SOLENOID
HOIST LEVER POSITION SENSOR
HOIST LOWER SOLENOID
41 ¥ EPTC III shifts the transmission electronically
The purpose of the EPTC III is to determine the desired transmission gear and energize solenoids to shift the transmission up or down as required based on information from both the operator and machine.
¥ Shifts controlled by electrical signals
The EPTC III receives information from various input components such as the shift lever sensor, Transmission Output Speed (TOS) sensor, transmission gear switch, body up switch and the hoist lever sensor. Based on the input information, the EPTC III 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.
NOTE: The torque Converter Output Speed (COS) sensor is not installed on the D-series update trucks.
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¥ EPTC III outputs
- 57 -
Output components include the upshift, downshift and lockup solenoids, the back-up alarm and others. The EPTC III also provides the service technician with enhanced diagnostic capabilities through the use of onboard memory, which stores possible diagnostic codes for retrieval at the time of service.
¥ Benefits of electronic communication
The Advanced Diesel Engine Management (ADEM II) engine control, the Automatic Retarder Control (ARC) and Traction Control System (TCS) control, the Caterpillar Monitoring System or the Vital Information Management System (VIMS) and the EPTC III all communicate with each other through the CAT Data Link. Communication between the electronic controls allows the sensors of each system to be shared. Many additional benefits are provided, such as Controlled Throttle Shifting (CTS). CTS occurs when the EPTC III tells the engine ECM to reduce engine fuel during a shift to lower stress to the power train.
¥ EPTC III used to control hoist and secondary steering system
The EPTC III is also used to control the hoist and secondary steering system on the D-series update trucks.
¥ Service tool diagnostic and programming functions
Some of the diagnostic and programming functions that the service tools can perform are:
The Electronic Control Analyzer Programmer (ECAP) and the Electronic Technician (ET) Service Tools can be used to perform several diagnostic and programming functions (see Slide No. 23).
- Display real time status of input and output parameters - Display the internal clock hour reading. - Display the number of occurrences and the hour reading of the first and last occurrence for each logged diagnostic code and event. - Display the definition for each logged diagnostic code and event. - Display load counters. - Display the lockup clutch engagement counter. - Display the transmission gear shift counter. - Program the top gear limit and the body up gear limit - Upload new Flash files INSTRUCTOR NOTE: In the following slides, only some of the input and output components of the transmission and chassis control will be shown. Other components will be shown when the system they control is discussed (hoist raise and lower solenoids for example).
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1. Shift lever sensor - PWM duty cycle input
The shift lever (also referred to as the "Cane" or "Gear Selector") sensor (1) is located inside the cab in the shift console and provides an input signal to the transmission and chassis control (EPTC III). The shift lever sensor controls the desired top gear selected by the operator. The sensor provides a PWM duty cycle signal that is unique for each position of the shift lever sensor.
¥ Shift lever diagnostics
To view the shift lever sensor positions or diagnose problems with the sensor, use Mode 7.5 of the Caterpillar Monitoring System display window or the status screen of the service tool and observe the "Gear Lever" status. As the shift lever is moved through the detent positions, the Gear Lever status should display the corresponding lever position shown on the shift console.
2. Shift lever adjustment nuts
The position of the shift lever can be changed to obtain better alignment with the gear position numbers on the shift console by loosening the three nuts (2) and rotating the lever. The position of the shift lever sensor is not adjustable.
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43 1. Service/retarder brake switch
¥ Service/retarder brakes engaged: - Raises shift points - Eliminates anti-hunt timer
The service/retarder brake switch (1) is located in the compartment behind the cab. The switch is normally closed and opens when service/retarder brake air pressure is applied. The switch has two functions for the EPTC III: - Signals the EPTC III to use elevated shift points, which provides increased engine speed during downhill retarding for increased oil flow to the brake cooling circuit. - Signals the EPTC III to allow rapid shifting during braking by overriding the anti-hunt timer. A diagnostic code is stored if the EPTC III does not receive a closed (ground) signal from the switch within seven hours of operation time or an open signal from the switch within two hours of operation time.
¥ Service/retarder switch used as TCS input
The Traction Control System (TCS) also uses the service/retarder brake switch as an input through the CAT Data Link (see Slide No. 80).
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2. Parking/secondary brake switch location ¥ Parking/secondary brakes engaged: - Eliminates anti-hunt timer - Signals parked machine
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The parking/secondary brake switch is in location (2) (trust me, it's in there somewhere) in the parking/secondary brake air pressure line. The normally open switch is closed during the application of air pressure. The purpose of the switch is to signal the EPTC III when the parking/ secondary brakes are engaged. Since the parking/secondary brakes are spring applied and pressure released, the parking/secondary brake switch is closed when the brakes are not applied and opens when the brakes are applied. This signal is used to override the anti-hunt timer for rapid downshifting and is used to sense when the machine is parked. A diagnostic code is stored if the EPTC III does not receive a closed (ground) signal from the switch within seven hours of operation time or an open signal from the switch within one hour of operation time.
3. Back-up alarm relay
The back-up alarm relay (3) is also located behind the cab. When the operator moves the shift lever to REVERSE, the EPTC III provides a signal to the back-up alarm relay, which turns ON the back-up alarm.
¥ Hoist lever sensor
Another input to the EPTC III is the hoist lever sensor (see Slide No. 124). The main function of the hoist lever sensor is to raise and lower the body, but it is also used to NEUTRALIZE the transmission. 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:
- Reverse inhibitor operation
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. ¥ Lockup solenoid
The EPTC III provides a Pulse Width Modulated (PWM) signal to the torque converter lockup solenoid to control the lockup clutch pressure (see Slide No. 33 and 34). When the lockup solenoid is energized, the lockup valve supplies oil to ENGAGE the lockup clutch in the torque converter.
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1 Body up switch 2. Magnet
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 by the switch and causes the switch to close. The resulting ground signal is sent to the EPTC III. This signal is used to limit the top gear into which the transmission will shift. The top gear value is programmable utilizing the ECAP or ET Service Tool. The EPTC III 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.
¥ Body up signal used for hoist snubber control
The body up switch signal is also used to control the snubber position of the hoist control valve. When the body is being lowered and the magnet passes by the body up switch, the transmission and chassis control (EPTC III) signals the hoist lower solenoid to move the hoist valve spool to the snubber position. In the snubber position, the body float speed is reduced to prevent the body from contacting the frame too hard.
¥ Body up switch must be adjusted
The snubber feature will only function if the body up switch is adjusted correctly.
¥ Body up diagnostic code
A diagnostic code occurs if the Electronic Control 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.
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STEERING SYSTEM ¥ Steering system requires less horsepower
The D-series update trucks use a load sensing, pressure compensated, type steering system which is a substantial change from the steering system used on the D-series pre-update trucks. Very little horsepower is used by the new 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.
¥ Steering system tank
Located on the right platform behind the air filters is the steering system tank.
1. Steering system oil level sight gauge
Check the steering system oil level at the sight gauge (1).
2. Steering system oil filter
The steering system oil filter (2) is located on the side of the steering tank. Steering system oil samples can be taken from the Scheduled Oil Sampling (S¥O¥S) tap (3) located on top of the steering filter.
3. Steering system S¥O¥S tap
4. Case drain oil filter screen 5. Steering tank pressure release button and breather
The steering system uses a pressure compensated piston type pump. Case drain oil from the steering pump returns to the hydraulic tank through a screen (4) that is part of the fitting installed in the side of the steering tank. Before removing the cap 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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46 1. Steering pump
2. High pressure cutoff valve - Main steering system relief
3. Flow compensator valve - Low pressure standby
4. Load sensing signal pressure port
The D-series update trucks are equipped with a load sensing, pressure compensated, piston-type pump (1). The steering pump is the third pump mounted in tandem to the engine flywheel housing. 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 (2) is used as the primary steering system relief valve. To adjust the primary steering system pressure setting (high pressure cutoff), loosen the jam nut and turn the adjusting screw IN to increase the pressure or OUT to decrease the pressure. The primary steering system pressure setting is 23500 ± 350 kPa (3400 ± 50 psi). To verify the new pressure setting, operate the truck in NEUTRAL with the engine at HIGH IDLE and turn the steering wheel hard against the stops to the left or right. The flow compensator valve (3) is used to adjust the low pressure standby pressure. When the truck is traveling in a straight path, there is virtually no flow or pressure required to the steering cylinders and the pump destrokes to low pressure standby. To adjust the low pressure standby setting, loosen the jam nut and turn the adjusting screw IN to increase the pressure or OUT to decrease the pressure. The low pressure standby setting should be between 2100 and 3600 kPa (300 and 525 psi). To verify the new pressure setting, operate the truck in NEUTRAL with the engine at HIGH IDLE and DO NOT turn the steering wheel. Load sensing (LS) signal pressure from the Hand Metering Unit (HMU) (see Slide No. 52) enters the load sensing controller at port (4).
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¥ Steering pump 1. Steering oil supply hose 2. Steering outlet hose 3. Case drain return hose
Shown is the steering pump in a 775D update truck. The steering pump pulls supply oil from the steering tank through hose (1). Steering oil flows from the pump through hose (2) to the steering valve located on the frame behind the right front suspension cylinder (see Slide No. 50). All piston type pumps produce a small amount of internal leakage for lubrication and cooling. The internal leakage is referred to as case drain oil and flows to the steering tank through hose (3). Before entering the steering tank, the case drain oil flows through a case drain screen (see Slide No. 45).
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LOAD SENSING PRESSURE FROM HMU
HIGH PRESSURE CUTOFF VALVE
TO STEERING VALVE AND HMU
STEERING PUMP LOW PRESSURE STANDBY
PUMP OUTPUT ACTUATOR PISTON
LOAD SENSING PRESSURE
FLOW COMPENSATOR LOAD SENSING CONTROLLER SWASHPLATE PISTON CASE DRAIN SCREEN
48 ¥ Steering pump at minimum flow low pressure standby
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 oil pressure of the swashplate piston and moves the swashplate to destroke the pump. The pump is then at minimum flow, low pressure standby.
¥ Low pressure standby setting
Pump output flow and pressure is equal to the setting of the flow compensator plus the pressure required to compensate for system leakage. The low pressure standby setting should be between 2100 and 3600 kPa (300 and 525 psi).
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LOAD SENSING PRESSURE FROM HMU
HIGH PRESSURE CUTOFF VALVE
TO STEERING VALVE AND HMU
STEERING PUMP MAXIMUM FLOW
PUMP OUTPUT ACTUATOR PISTON
LOAD SENSING PRESSURE
FLOW COMPENSATOR LOAD SENSING CONTROLLER SWASHPLATE PISTON CASE DRAIN SCREEN
49 ¥ Steering pump at maximum flow
During a turn, when steering pressure and flow is 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 travel 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. Steering pressure switch
Steering oil flows from the pump to the steering valve located on the frame behind the right front suspension cylinder. A steering pressure switch (1) monitors the output of the steering pump. The steering pressure switch provides input signals to the transmission and chassis control and the Caterpillar Monitoring System or the VIMS informs the operator of the condition of the steering system. A steering system warning is displayed if the pressure in the steering system drops below 700 ± 100 kPa (100 ± 15 psi).
2. Pressure reducing valve
The steering pressure switch cannot tolerate high steering system pressures. A pressure reducing valve (2) reduces steering system pressure to the steering pressure switch. The setting of the pressure reducing valve is 2070 kPa (300 psi). To check the setting of the pressure reducing valve, remove the steering pressure switch and install a gauge in the switch port.
¥ Secondary steering
If the steering pressure switch signals the transmission and chassis control that the steering system pressure is low, the transmission and chassis control will energize the secondary steering relay located behind the cab. The secondary steering relay will then turn ON the secondary steering motor (see Slide No. 53). Secondary steering supply oil flows to the steering valve through hose (3).
3. Secondary steering supply hose
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4. Secondary steering backup relief valve
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 setting of the secondary steering back-up relief valve is 17300 ± 300 kPa (2500 ± 45 psi). Secondary steering pressure is first controlled by a relief valve located in the secondary steering pump load sensing valve. The setting of the relief valve in the secondary steering pump load sensing valve is 15150 ± 300 kPa (2200 ± 45 psi).
¥ Secondary steering backup relief valve adjustment
To check the setting of the secondary steering back-up relief valve, increase the setting of the relief valve in the secondary steering pump load sensing valve. Count the number of turns made to the adjustment screw so the valve can be put back to its original setting. Loosen the jam nut on the secondary steering back-up relief valve and turn the adjusting screw IN to increase the pressure or OUT to decrease the pressure. To verify the new pressure setting, do not start the truck. Turn ON the key start switch and depress the secondary steering switch located on the dash (see Slide No. 18). Turn the steering wheel hard to the left or right while the secondary steering pump is running.
¥ Primary steering backup relief valve
The lower relief valve 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 cutoff valve on the steering pump malfunctions. The setting of the primary steering back-up relief valve is 25500 ± 300 kPa (3700 ± 45 psi). Primary steering pressure is first controlled by the high pressure cutoff valve located on the steering pump. The setting of the high pressure cutoff valve on the steering pump is 23500 ± 350 kPa (3400 ± 50 psi).
¥ Primary steering backup relief valve adjustment
To check the setting of the primary steering back-up relief valve, increase the setting of the high pressure cutoff valve on the steering pump. Count the number of turns made to the adjustment screw so the valve can be put back to its original setting. Loosen the jam nut on the primary steering back-up relief valve and turn the adjusting screw IN to increase the pressure or OUT to decrease the pressure. To verify the new pressure setting, operate the truck in NEUTRAL with the engine at HIGH IDLE and turn the steering wheel hard against the stops to the left or right.
5. Steering system pressure tap
Connect a pressure gauge at tap (5) when checking the primary steering system pressures and the secondary steering system pressures.
6. HMU supply hose
Steering supply oil flows to the HMU through hose (6). Return oil from the HMU flows through hose (7), the steering valve and the large hose located above the steering pressure switch. The large hose above the steering pressure switch returns steering oil through the steering filter to the steering tank.
7. HMU return hose ¥ Steering return hose to tank
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¥ Check valve plugs (arrows) - Secondary check valve (top) - Primary check valve (bottom)
Shown is a front view of the steering valve. Located behind the two plugs (arrows) are two check valves. The check valves are used to separate the primary and secondary steering systems. The secondary check valve is behind the top plug and the primary check valve is behind the bottom plug.
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52 1. HMU
The Hand Metering Unit (HMU) (1) is located at the base of the steering column behind a cover at the front of the cab. The HMU is connected to the steering wheel and controlled by the operator.
¥ Meters oil to steering cylinders
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.
¥ Q-amp steering system
The steering system is referred to as "Q-amp" which means flow amplification. During a sudden steering change, 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 by up to 1.6 to 1. The purpose of the flow amplification is to provide quick steering response when sudden steering changes are needed.
2. Load sensing signal line
Load sensing signal pressure flows through hose (2) to the load sensing controller on the primary steering pump (see Slide No. 46) and the load sensing controller on the secondary steering pump (next slide).
¥ HMU hoses
On the front of the HMU are four hoses. The four hoses are: - Top left hose--return to tank - Top right hose--left turn - Bottom left hose--pump supply - Bottom right hose--right turn
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¥ HMU crossover relief valves
Located in the top of the HMU are two crossover relief valves. 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 other end of the cylinders. The setting of the crossover relief valves is 27200 kPa (3950 psi).
¥ Right crossover relief valve pressure test
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 all the way 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.
¥ Left crossover relief valve pressure test
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 all the way 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. On D-series pre-update trucks a separate crossover relief valve block was located on the frame in the engine compartment.
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1. Secondary steering pump
2. Secondary steering motor 3. Secondary steering pump load sensing valve 4. Load sensing solenoid 5. Load sensing signal pressure fitting
The secondary steering pump (1) is mounted under the rear engine frame above the torque converter. If the steering pressure switch (see Slide No. 50) signals the transmission and chassis control that the steering system pressure is low, the transmission and chassis control will energize the secondary steering relay located behind the cab. The secondary steering relay will then turn ON the secondary steering motor (2). Secondary steering supply oil flows to the steering valve from the secondary steering pump load sensing valve (3). When the transmission and chassis control energizes the secondary steering motor, it also de-energizes the load sensing solenoid (4). When de-energized, the solenoid allows load sensing signal pressure to flow from the HMU through fitting (5) to the load sensing valve. The load sensing valve uses the load sensing signal to control the amount of pressure in the secondary steering circuit.
¥ Secondary steering relief valve
The primary relief valve for the secondary steering circuit is in the load sensing valve. The setting of the relief valve is 15150 ± 300 kPa (2200 ± 45 psi). The relief valve is accessible through the small allen head plug on the bottom of the load sensing valve and closest to the pump.
6. Towing brake retraction pump
Pump (6) is used to release the parking brakes for service work or towing. Before the pump will provide oil to release the brakes, a diverter (towing) valve must be shifted (see Slide No. 71). Normally oil flows from the pump directly to the hoist and brake oil tank.
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STEERING HYDRAULIC SYSTEM
L
STEERING TANK
T LS
STEERING FILTER
P R
CASE DRAIN SCREEN
HMU
PRIMARY STEERING PUMP LOAD SENSING VALVE
SECONDARY CHECK VALVE
SECONDARY STEERING BACK-UP RELIEF VALVE
SECONDARY STEERING PUMP
LOAD SENSING SOLENOID
STEERING PRESSURE SWITCH
PRESSURE REDUCING VALVE STEERING VALVE STEERING VALVE (REAR) (FRONT) PRIMARY CHECK VALVE
PRIMARY STEERING BACK-UP RELIEF VALVE
54 ¥ Steering hydraulic system
Shown is the steering hydraulic system. The primary steering pump pulls supply oil from the steering tank. All piston type pumps produce a small amount of leakage to case drain for lubrication and cooling. The case drain oil flows to the steering tank through a case drain screen.
¥ Steering pressure switch
Steering oil flows from the pump to the steering valve located on the frame behind the right front suspension cylinder. 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 reduces steering system pressure to the steering pressure switch.
¥ Pressure reducing valve
¥ Secondary steering
If the steering pressure switch signals the transmission and chassis control that the steering system pressure is low, the transmission and chassis control will turn ON the secondary steering motor and turn OFF the secondary steering load sensing solenoid. Secondary steering supply oil flows to the steering valve.
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¥ Secondary steering load sensing solenoid
When the transmission and chassis control energizes the secondary steering motor, it also de-energizes the load sensing solenoid. When de-energized, the solenoid allows load sensing signal pressure to flow from the HMU to the secondary steering load sensing valve. The load sensing valve uses the load sensing signal to control the amount of flow from the secondary steering pump to the steering valve.
¥ Secondary steering back-up relief valve
Two relief valves are located on the steering valve. The top relief valve 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.
¥ Primary steering back-up relief valve
The lower relief valve 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 cutoff valve on the steering pump malfunctions.
¥ Primary and secondary steering check valves
Two check valves are located on the steering valve. The check valves are used to separate the primary and secondary steering systems.
¥ HMU
On the HMU are five ports. The five ports are: - T--Tank - L--Left turn - P--Pump supply - R--Right turn - LS--Load sensing The Hand Metering Unit (HMU) is located at the base of the steering column behind a cover at the front of the cab. The HMU is connected to the steering wheel and controlled by the operator. Steering supply oil flows to the HMU (P) from the steering valve. Return oil from the HMU (T) 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 (L and R) 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. Load sensing (LS) signal pressure flows to the load sensing controller on the primary steering pump and the load sensing solenoid valve on the secondary steering pump.
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CROSSOVER RELIEF VALVES
STEERING HYDRAULIC SYSTEM
HMU
LOAD SENSING SOLENOID
PRESSURE REDUCING VALVE STEERING PRESSURE SWITCH
LOAD SENSING VALVE M
PRIMARY STEERING BACK-UP RELIEF VALVE
STEERING FILTER
EPTC III
SECONDARY STEERING BACK-UP RELIEF VALVE
SECONDARY STEERING PRIMARY RELIEF VALVE
SECONDARY STEERING PUMP
55 ¥ Steering hydraulic system ISO schematic
Shown is an ISO schematic of the steering hydraulic system used in the D-series update trucks. All of the internal valve components and the direction of oil flow can be seen. The components are discussed in more detail when the iron is shown in the previous slides.
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HOIST SYSTEM ¥ Hoist system controlled by EPTC III
The hoist system on the D-series update trucks is electronically controlled by the Transmission and Chassis Control, sometimes referred to as the third generation Electronic Programmable Transmission Control (EPTC III).
¥ Hoist lever (arrow)
The operator controls the hoist lever (arrow). The four positions of the hoist lever are RAISE, HOLD, FLOAT and LOWER.
¥ Hoist lever normally in FLOAT position
The truck should normally be operated with the hoist lever in the FLOAT position. Operating with the hoist lever in the FLOAT position allows the hoist valve to provide some downward hydraulic pressure on the hoist cylinders and prevents an empty body from bouncing on rough haul roads.
¥ Hoist snubber control
The hoist valve has a fifth position referred to as the snubber position. The operator is unaware of the snubber position because there is no corresponding lever position. When the body is being lowered, just before the body contacts the frame, the EPTC III signals the hoist lower solenoid to move the hoist valve spool to the snubber position. In the snubber position, the body float speed is reduced to prevent the body from contacting the frame too hard.
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¥ Hoist control position sensor (arrow) ¥ Sensor energizes two solenoids on hoist valve
The hoist lever controls a Pulse Width Modulated (PWM) position sensor (arrow). The PWM sensor sends duty cycle input signals to the EPTC III. Depending on the position of the sensor and the corresponding duty cycle, one of the two solenoids located on the hoist valve is energized.
¥ Hoist lever sensor provides modulation
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.
¥ Sensor performs three functions:
The hoist lever sensor also replaces the body raise switch (transmission neutralizer switch) that was located behind the operatorÕs seat. The hoist lever sensor performs three functions:
- Raises and lowers body - Neutralizes transmission in REVERSE - Starts cycle for TPMS
- Raises and lowers the body. - Neutralizes the transmission in REVERSE. - Starts a cycle for the Truck Production Management System (TPMS).
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¥ Hoist and brake hydraulic tank 1. Oil level sight gauge door ¥ Use only TDTO oil
Shown is the hoist and brake hydraulic tank. The oil level is checked by opening the small door (1) and looking through 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. Use only Transmission Drive Train Oil (TDTO) with a specification of (TO-4) or newer. - TDTO TO-4 provides maximum frictional capability required for clutch discs used in the brakes. - Increases brake holding capability by reducing brake slippage. - Controls brake chatter.
2. Breather
Check the hoist and brake hydraulic tank breather (2) for plugging (cover removed for visibility). Clean the filter if plugged. If oil is flowing from the filter, the hoist and brake hydraulic tank may be overfilled.
3. Return screen cover
Hoist and brake cooling oil returns to the hydraulic tank through a screen located below cover (3).
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¥ Rear of hoist and brake oil tank ¥ Suction screen (arrow)
Shown is the rear of the hoist and brake oil hydraulic tank. The hoist pump pulls oil from the hydraulic tank through the suction screen (arrow) located in the rear of the tank.
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1. Hoist pump
The hoist pump (1) is the first of three pumps mounted in tandem to the engine flywheel housing. Oil flows from the hoist pump to the hoist valve.
2. Parking brake retraction pump supplies hoist pilot oil
The parking brake retraction pump (2) supplies oil to release the parking brakes and cool the brakes and is also used as pilot oil for the hoist valve.
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¥ Hoist control valve 1. Hoist oil supply hose 2. Pilot oil supply hose
3. RAISE position solenoid valve 4. LOWER position solenoid valve
¥ Hoist solenoids "dither" in the HOLD position
Oil flows from the hoist pump through hose (1) to the hoist control valve located inside the right frame next to the torque converter. The hoist valve uses brake retraction oil as the pilot oil to shift the directional spool inside the hoist valve. Brake retraction oil enters the hoist valve through hose (2). The brake retraction oil pressure is 3170 ± 200 kPa (460 ± 30 psi) on 769D/771D trucks and 4700 ± 200 kPa (680 ± 30 psi) on 773D/775D trucks. 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 (3) and the solenoid on the left is the LOWER solenoid valve (4). The RAISE and LOWER solenoid valves are always receiving approximately 300 milivolts at a frequency of 80 Hz when they are in the HOLD position. The excitation, referred to as "dither," is used to keep the solenoids in a ready state for quick response.
NOTE: On the 769D/771D update pilot trucks, the brake retraction oil pressure is 4700 ± 200 kPa (680 ± 30 psi). Brake retraction oil pressures may be changed later.
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¥ Hoist solenoids receive between 0 and 1.9 amps
When the EPTC III receives an input signal from the hoist lever sensor, the EPTC III 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.
5. Hose to oil cooler
When the hoist valve is in the HOLD or FLOAT position, all the hoist pump oil flows through the large hose (5) to the hoist and brake oil cooler located on the right side of the engine. Excess oil from the brake retraction valve joins the hoist pump oil at the fitting connected to the large hose.
6. Oil cooler relief valve plug
An oil cooler relief valve is located in the hoist valve behind the large plug (6). The relief valve limits the brake oil cooling pressure when the hoist valve is in the HOLD or FLOAT position. The setting of the oil cooler relief valve is 586 ± 14 kPa (85 ± 2 psi).
¥ Relief pressures different for RAISE and LOWER
The hoist system relief pressures are different in the RAISE and LOWER positions. The RAISE relief valve (7) controls the pressure in the hoist system during RAISE. The hoist system relief pressure during RAISE is:
7. RAISE relief valve
769D/771D/773D 775D 8. LOWER relief valve
17225 + 520 - 0 kPa (2500 + 75 - 0 psi). 18950 + 520 - 0 kPa (2750 + 75 - 0 psi).
The LOWER relief valve (8) controls the pressure in the hoist system during LOWER. The hoist system relief pressure during LOWER is 3450 + 350 - 0 kPa (500 + 50 - 0 psi).
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¥ Two-stage hoist cylinders
Shown are the twin two-stage hoist cylinders used to raise the body. Oil flows from the hoist valve to the two hoist cylinders when the directional spool in the hoist valve is not in HOLD.
¥ Lower body with dead engine
To lower the body with a dead engine, air pressure and hoist pilot pressure are required. The towing pump can be used to provide the hoist pilot oil, but the parking brakes will be released at the same time. Use the retarder brakes to prevent the truck from rolling when the parking brakes are released. To lower the body with a dead engine, follow the steps below: - Block the wheels so the machine cannot move. - Move the diverter (towing) valve to the towing position (see Slides No. 152 and 153). - Approximately 550 kPa (80 psi) air pressure must be available to shift the spool in the brake retraction valve so when the parking brakes are released the hoist pilot oil does not flow to tank. - Engage the retarder brakes. - Release the parking brakes. - Turn ON the key start switch so the towing motor and the hoist solenoids can be energized. - Move the hoist lever to the RAISE position for 15 seconds, then to the FLOAT position. - Depress the secondary steering and brake retraction switch on the dash (see Slide No. 18).
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63
¥ Hoist system pressure taps (arrows) - RAISE pressure (bottom) - LOWER pressure (top) ¥ Orifice plate
Located on the bottom of the left hoist cylinder are the two hoist system pressure taps (arrows). The top tap is used to measure the LOWER hoist pressure. The bottom tap is used to measure the RAISE hoist pressure. The relief valve pressure setting is tested with the engine at HIGH IDLE and the hoist valve in the RAISE or LOWER position. 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 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).
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HOIST HYDRAULIC SYSTEM
OIL COOLER BRAKE RETRACTION PUMP
REAR BRAKES
HOIST PUMP HOIST VALVE
HYDRAULIC TANK
BRAKE RETRACTION VALVE
HOIST CYLINDERS
64 ¥ Hoist hydraulic system
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 valve. The hoist valve uses brake retraction oil as the pilot oil to shift the directional spool inside the hoist valve. Oil flows from the brake retraction valve to both ends of the hoist valve. The brake retraction oil pressure is 3170 ± 200 kPa (460 ± 30 psi) on 769D/771D trucks and 4700 ± 200 kPa (680 ± 30 psi) on 773D/775D trucks. 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.
NOTE: On the 769D/771D update pilot trucks, the brake retraction oil pressure is 4700 ± 200 kPa (680 ± 30 psi). Brake retraction oil pressures may be changed later.
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¥ Hoist and brake retraction oil flows to oil cooler and brakes
When the hoist valve is in the HOLD or FLOAT position, all the hoist pump oil flows through the hoist and brake oil cooler located on the right side of the engine. Excess oil from the brake retraction valve joins the hoist pump oil and also flows to the oil cooler. Oil flows from the oil cooler through the rear brakes and returns to the hydraulic tank through the return screen.
¥ Oil cooler relief valve
An oil cooler relief valve is located in the hoist valve. The relief valve limits the brake oil cooling pressure when the hoist valve is in the HOLD or FLOAT position. The setting of the oil cooler relief valve is 586 ± 14 kPa (85 ± 2 psi).
¥ Relief pressures different for RAISE and LOWER
The hoist system relief pressures are different in the RAISE and LOWER positions. Two relief valves control hoist system pressure, one for RAISE and one for LOWER. The hoist system relief pressure during RAISE is: 769D/771D/773D 775D -
17225 + 520 - 0 kPa (2500 + 75 - 0 psi). 18950 + 520 - 0 kPa (2750 + 75 - 0 psi).
The hoist system relief pressure during LOWER is 3450 + 350 - 0 kPa (500 + 50 - 0 psi). Oil flows from the hoist valve to the two hoist cylinders when the directional spool in the hoist valve is not in HOLD.
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BRAKE RETRACTION PUMP
HOIST HYDRAULIC SYSTEM BRAKE RETRACTION VALVE
BRAKE RETRACTION FILTER
LOWER RELIEF VALVE
HOIST PUMP
REAR BRAKES
OIL COOLER AND SCREEN
ORIFICE PLATES
HYDRAULIC TANK
RAISE RELIEF VALVE
HOIST CYLINDERS
DUAL STAGE SIGNAL SPOOL
BRAKE COOLING RELIEF VALVE
LOWER SOLENOID
RAISE SOLENOID
POWER DOWN
RAISE
FLOAT SNUBBER HOLD
MAIN RELIEF DUMP SPOOL
65 ¥ Hoist hydraulic system ISO schematic
Shown is an ISO schematic of the hoist hydraulic system used in the D-series update trucks.
¥ Directional spool operation
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 centering springs and the pressure on the opposite end of the spool to move the spool. The solenoid on the left is the RAISE solenoid valve and the solenoid on the right is the LOWER solenoid valve. When the RAISE solenoid is energized, the directional spool will move toward the RAISE solenoid.
¥ Hoist solenoids "dither" in the HOLD position
The RAISE and LOWER solenoid valves are always receiving approximately 300 milivolts at a frequency of 80 Hz when they are in the HOLD position. The excitation, referred to as "dither," is used to keep the solenoids in a ready state for quick response.
UPDATE 97
¥ Hoist lever sensor provides modulation
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The hoist lever controls a Pulse Width Modulated (PWM) position sensor. The PWM sensor sends duty cycle input signals to the EPTC III. 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 position of the hoist lever, the operator can modulate the speed of the hoist cylinders.
¥ Hoist solenoids receive between 0 and 1.9 amps
When the EPTC III receives an input signal from the hoist lever sensor, the EPTC III 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.
¥ Hoist lever normally in FLOAT position
The truck should normally be operated with the hoist lever in the FLOAT position. Operating with the hoist lever in the FLOAT position allows the hoist valve to provide some downward hydraulic pressure on the hoist cylinders and prevents an empty body from bouncing on rough haul roads.
¥ Hoist snubber control
The hoist valve has a fifth position referred to as the snubber position. The operator is unaware of the snubber position because there is no corresponding lever position. When the body is being lowered, just before the body contacts the frame, the body float speed is reduced to prevent the body from contacting the frame too hard.
¥ Body up signal used for hoist snubber control
A body up switch is located on the frame near the body pivot pin. When the body is raised, a magnet mounted on the body passes by the switch and causes the switch to close. When the body is lowered the switch will open. These signals are sent to the EPTC III. The body up switch signal is used to control the snubber position of the hoist control valve. When the body is being lowered and the magnet passes by the body up switch, the EPTC III signals the hoist lower solenoid to move the hoist valve spool to the snubber position.
¥ Body up switch must be adjusted
The snubber feature will only function if the body up switch is adjusted correctly.
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¥ RAISE position
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When the hoist 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 the spool to the left. When the dual stage signal spool moves to the left, pump supply oil is blocked from the LOWER relief valve and the RAISE relief valve will control the hoist system pressure. The hoist system relief pressure during RAISE is: 769D/771D/773D 775D -
¥ LOWER position
17225 + 520 - 0 kPa (2500 + 75 - 0 psi). 18950 + 520 - 0 kPa (2750 + 75 - 0 psi).
When the hoist valve is in the LOWER (POWER DOWN), FLOAT or SNUBBER 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 holds the spool in the 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. The hoist system relief pressure during LOWER is 3450 + 350 - 0 kPa (500 + 50 - 0 psi).
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1
2
66
AIR SYSTEM AND BRAKES 1. Service/retarder brake reservoirs
Air flows through the air dryer and fills three reservoirs. The two service/retarder brake reservoirs (1) are located on the right platform.
2. Check valve
A check valve (2) prevents a loss of air if an air line breaks upstream of the air reservoirs.
¥ Relief valve
A relief valve is installed in the service/retarder brake reservoirs. This relief valve serves as a back-up for the relief valve on the air dryer. The third reservoir is located behind the cab and supplies air for the parking/secondary brake system.
¥ Drain condensation
Condensation should be drained from the tanks daily through the drain valve located on the right platform (see Slide No. 13).
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AIR CHARGING SYSTEM
AIR COMPRESSOR AND GOVERNOR
RELIEF VALVE
AIR DRYER
ONE WAY CHECK VALVE
AIR RESERVOIR (SERVICE)
AIR RESERVOIR (SERVICE)
CAB ENCLOSURE
AIR PRESSURE SENSOR
WIPER MOTOR
DRAIN VALVE
PRESSURE PROTECTION VALVE HORN VALVE
WINDSHIELD WIPER VALVE WIPER NOZZLE
PARKING/ SECONDARY RESERVOIR
WIPER FLUID BOTTLE
AIR HORN
67 ¥ Air charging system schematic
This schematic shows the flow of air through the air charging system. Air flows from the air compressor, through the air dryer, to the service/retarder brake reservoirs. Air from the service/retarder brake reservoirs enters the pressure protection valve. When the pressure in the service/retarder reservoirs reaches 550 kPa (80 psi), the pressure protection valve allows air to flow to the parking/secondary brake reservoir and the accessory circuits (wiper and horn). All reservoirs have a check valve at the air supply port to prevent a loss of air if a leak upstream of the reservoirs occurs. The air system pressure sensor provides an input signal to the Caterpillar Monitoring System or the VIMS which informs the operator if air system pressure is low.
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2
1 4
3
5
68 Brake Systems 1. Service brake valve - Engages front and rear brakes 2. Automatic Retarder Control (ARC) valve ¥ Front brake ON/OFF switch and front brake ratio valve
3. Left double check valve ¥ Service brake and manual retarder engage rear brake relay valve
4. Right double check valve 5. Retarder ON switch
The service brake valve (1) is controlled by the brake pedal in the cab. Supply air for the service brake valve, the manual retarder valve and the Automatic Retarder Control (ARC) valve (2) is supplied from the bottom port of the service brake valve. When the service brakes are engaged, air flows from the service brake valve to the front brake ON/OFF switch. If the front brake ON/OFF switch is ON, air flows through the front brake ratio valve to the front brake relay valve near the brake master cylinders. Air from the service brake valve also flows through the left double check valve (3) to the rear brake relay valve near the brake master cylinders. Air from the manual retarder valve also flows through the left double check valve. If the manual retarder and the service brakes are engaged at the same time, air from the system with the highest pressure will flow through the left double check valve to the rear brake relay valve. Air from the manual retarder valve also flows through the right double check valve (4) to the retarder ON switch (5) and the stop light switch and transmission service/retarder brake switch (see Slide No. 43). The retarder ON switch turns on the amber retarder lamp on the dash in the operatorÕs station when the manual or automatic retarder is ENGAGED (see Slide No. 17).
UPDATE 97
¥ ARC brake system engages separate relay valve
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The Automatic Retarder Control (ARC) system function is to modulate truck braking (retarding) when descending a long grade to maintain a constant engine speed. On D-series pre-update trucks, the ARC was installed in parallel with the manual retarder and the service brakes. On D-series update trucks, the ARC system is separate from the manual retarder and the service brakes. When the ARC is engaged, air flows from the ARC valve to a separate ARC relay valve located near the brake master cylinders. Air also flows from the ARC valve through the right double check valve to the retarder ON switch and the stop light switch and transmission service/retarder brake switch.
INSTRUCTOR NOTE: The ARC system will be discussed in more detail in the ARC section of this meeting guide.
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2 6
5
4
1
3
69
1. Service brake and manual retarder relay valve 2. Brake cylinder double check valve
The rear brake relay valve (1) receives metered air from only the service brake valve or the manual retarder valve. When the service brakes or manual retarder brakes are ENGAGED, the rear brake relay valve opens and metered air flows from the service brake reservoir, through the brake cylinder double check valve (2), to the rear brake cylinder.
3. ARC relay valve
The ARC relay valve (3) receives metered air from only the Automatic Retarder Control (ARC) valve. When the ARC brake system is ENGAGED, the ARC relay valve opens and metered air flows from the service brake reservoir, through the brake cylinder double check valve, to the rear brake cylinder.
¥ Brake relay valves reduce time to engage and release brakes
The brake relay valves reduce the time required to engage and release the brakes.
¥ Double check valve separates brake systems
The brake cylinder double check valve is used to separate the service brakes and manual retarder brakes from the ARC brake system.
UPDATE 97
4. Front brake relay valve 5. Front brake double check valve
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The front brake relay valve (4) receives metered air from the service brake valve only if the front brake ON/OF switch is in the ON position. When the service brakes are ENGAGED, if the front brake ON/OF switch is ON, the front brake relay valve opens and metered air flows from the service brake reservoir, through the front brake double check valve (5) to the front brake cylinder. The front brake double check valve prevents air from flowing through the inversion valve exhaust port when the service brakes are engaged.
6. Inversion valve - Engages front brakes
The inversion valve (6) is used to ENGAGE the front brakes with the secondary brake lever, even if the front brake ON/OFF switch is OFF. Supply air from the parking/secondary brake reservoir is present at the supply passage of the inversion valve. When the secondary brake lever is pulled, the secondary brake valve blocks the flow of air to the control passage of the inversion valve. Removing air pressure from the control passage of the inversion valve allows supply air pressure to flow through the inversion valve and the front brake double check valve to the front brake cylinder and engage the front brakes.
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3
2
1
70
1. Electric motor 2. Towing pump
If the parking brakes need to be released for service work or towing, the electric motor (1) can be energized by the brake retraction switch located in the cab (see Slide No. 18). The motor drives the a pump (2) which sends oil through a diverter (towing) valve to the brake retraction valve to RELEASE the parking brakes. Towing pump pressure is controlled by the relief valve in the brake retraction valve.
¥ Air pressure needed to release brakes for towing
Air pressure is also needed to release the brakes for towing. The piston chamber in the brake retraction valve must be pressurized to move the spool in the valve. The oil from the electrically driven brake release pump can then flow to the rear brakes.
3. Secondary steering pump
Pump (3) is used for secondary steering (see Slide No. 53).
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71
¥ Diverter valve (arrow)
The diverter (towing) valve (arrow) must be shifted before towing. The diverter valve is located on the rear of the hydraulic tank.
¥ Towing pump oil flows to hydraulic tank during secondary steering test
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.
¥ Shift diverter valve for towing
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. Now, when the electric motor is energized, supply oil can flow from the towing pump through the diverter valve to the parking brake retraction valve.
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¥ Procedure to check parking brake release system for towing
To check the brake retraction system used for towing, install a gauge on a parking brake pressure tap on the rear axle. Use a long gauge hose so the gauge can be held in the cab. With the parking brake air switch in the RELEASE position and the key start switch in the ON position, energize the parking brake retraction switch on the dash used for towing. The parking brake retraction pressure should increase to 3170 ± 200 kPa (460 ± 30 psi) on 769D/771D trucks and 4700 ± 200 kPa (680 ± 30 psi) on 773D/775D trucks, which is the setting of the relief valve in the brake retraction valve. Turn off the switch when the pressure stops increasing.
¥ Parking brake release pressures
The parking brakes start to release between 2580 and 2760 kPa (375 and 400 psi) on 769D/771D trucks and 3100 and 3445 kPa (450 and 500 psi) on 773D/775D trucks. Parking brake release pressure must not be below these pressure or the brakes will drag. The parking brakes are fully released between 2860 and 3170 kPa (415 and 460 psi) on 769D/771D trucks and 3445 and 3860 kPa (500 and 560 psi) on 773D/775D trucks.
NOTE: At least 550 kPa (80 psi) air pressure must be available at the parking brake retraction valve to ensure full release of the brakes for towing. NOTE: On the 769D/771D update pilot trucks, the brake retraction oil pressure is 4700 ± 200 kPa (680 ± 30 psi). Brake retraction oil pressures may be changed later.
NOTICE Energize the brake retraction switch only when additional pressure is required to release the brakes. Leaving the brake retraction (towing) motor energized continuously will cause damage to the motor. The parking brake release pressure setting must not exceed 4200 kPa (610 psi) on 769D/771D trucks or 5445 kPa (790 psi) on 773D/775D trucks. Exceeding these pressures can cause internal damage to the brake assembly.
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AIR SUPPLY FROM PARKING BRAKE AIR SWITCH
BRAKE RETRACTION DURING TOWING
PARKING BRAKE RETRACTION VALVE
RELIEF VALVE HOIST VALVE PILOT SUPPLY
PARKING BRAKE RETRACTION PUMP AND FILTER
CHECK VALVE
DIVERTER VALVE
DIVERTER VALVE CLAMP BOLTS
TOWING PUMP
SECONDARY STEERING PUMP
72 ¥ Parking brake system - During towing
Shown is a schematic of the parking brake system during TOWING with the parking brakes released.
¥ Towing pump is energized with secondary steering/brake retraction switch
If the parking brakes need to be released for service work or towing, an electric motor can be energized with the secondary steering/brake retraction switch on the dash in the cab. The electric motor then drives two pumps. One pump provides supply oil for releasing the parking brakes and the second pump supplies oil for secondary steering.
¥ Diverter valve must be shifted before towing
A diverter valve must be shifted before the towing pump can supply oil to the parking brake system. 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. Now, when the electric motor is energized, supply oil will flow from the towing pump through the diverter valve to the parking brake retraction valve.
UPDATE 97
¥ Check valve prevents oil flow to normal parking brake retraction pump ¥ Air supply required for towing ¥ Brake release pressure controlled by relief valve in parking brake retraction valve
- 100 -
A check valve prevents towing pump supply oil from flowing to the normal parking brake retraction pump. Towing supply oil flows through the parking brake retraction valve to release the parking brakes as long as supply air is available from the parking brake air switch in the cab. During towing and normal operation, the brake release pressure is controlled by the relief valve located in the parking brake retraction valve.
NOTE: Before normal operation of the parking brake release system can occur, the diverter valve must be shifted back to its normal operating position.
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PARKING/SECONDARY BRAKE SYSTEM SECONDARY BRAKES ENGAGED RELAY VALVE (FRONT)
SECONDARY BRAKE VALVE
PARKING BRAKE AIR SWITCH
DOUBLE CHECK VALVE
PARKING/ SECONDARY BRAKE SWITCH INVERSION VALVE
BRAKE CYLINDER ( FRONT )
BRAKE RETRACTION VALVE
PARKING/SECONDARY AIR RESERVOIR HOIST VALVE PILOT SUPPLY
73 ¥ Parking/secondary brake system
Shown is the parking/secondary brake system with the secondary brakes ENGAGED.
¥ Secondary brake valve controls air flow to:
Supply air from the parking/secondary brake reservoir is present at the supply passage of the secondary brake valve and the inversion valve. When the secondary brake lever is pulled, the secondary brake valve blocks the flow of air to the parking/secondary brake switch, the parking brake retraction valve and the control passage of the inversion valve.
- parking/secondary brake switch - brake retraction valve - inversion valve
Removing air pressure from the parking/secondary brake switch causes the EPTC III to eliminate the anti-hunt timer and allow rapid downshifts. Removing air pressure from the parking brake retraction valve allows oil from the parking brake to drain through the brake retraction valve, which allows the springs in the parking brake to ENGAGE the brakes.
¥ Inversion valve engages front brakes
Removing air pressure from the control passage of the inversion valve allows supply air pressure to flow through the inversion valve and the double check valve to the front brake cylinder and engage the front brakes. The double check valve prevents air from flowing through the inversion valve exhaust port when the service/retarder brakes are engaged.
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SERVICE/RETARDER BRAKE SYSTEM FRONT BRAKE VALVE OFF SERVICE BRAKES ENGAGED RETARDER RELEASED ARC OFF
AIR RESERVOIR (SERVICE)
RELIEF VALVE
ONE WAY CHECK VALVE AIR RESERVOIR (SERVICE)
CAB ENCLOSURE
FRONT BRAKE ON/OFF SERVICE VALVE BRAKE CONTROL VALVE
DRAIN VALVE RETARDER VALVE
AIR PRESSURE SENSOR
FRONT BRAKE RATIO VALVE
RELAY VALVE (FRONT)
BRAKE CYLINDER ( FRONT )
ARC VALVE
RELAY VALVE (SERVICE/ RETARDER)
RELAY VALVE (ARC)
BRAKE CYLINDER ( REAR )
STOP LIGHT AND TRANSMISSION SERVICE/RETARDER SWITCH
RETARDER SWITCH
74 ¥ Service/retarder brake air system
This schematic shows the flow of air through the service/retarder brake air system. In this schematic, the front brake ON/OFF valve is in the OFF position and the service brake control valve is ENGAGED. The retarder valve is in the RELEASED position and the ARC is OFF. Supply air pressure flows from the service brake air reservoirs to the relay valves and through the air system pressure sensor to the service brake valve. Supply air pressure flows from the service brake valve to the retarder valve and the ARC valve. The retarder valve blocks the flow of air to three double check valves. The ARC valve blocks the flow of air to two double check valves and the ARC relay valve.
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¥ Front brake ON/OFF valve controls air flow to front brake cylinder
With the front brake ON/OFF switch in the OFF position and the service brake pedal depressed, only the rear service brakes are ENGAGED. Air flows from the service brake control valve to the front brake ON/OFF valve and is blocked.
¥ Service brake energizes two brake switches
Air also flows from the service brake control valve, through a double check valve, to the stop light switch and the transmission service/retarder brake switch. Depressing the service brake pedal turns ON the brake lights, and changes the transmission shift points and anti-hunt timer. Air also flows from the service brake control valve, through a double check valve, to the service and manual retarder brake relay valve. The service and manual retarder brake relay valve opens and allows air from the service brake reservoirs to flow through a double check valve to the rear brake cylinder. Air from the service and manual retarder brake relay valve compresses the piston in the rear brake cylinder and ENGAGES the rear brakes.
¥ Manual retarder operation - Energizes three brake switches
- Engages only rear brakes
¥ ARC operation - Energizes three brake switches
- Engages only rear brakes
When the retarder lever is moved, air flows through three double check valves. Air flows from the retarder valve through a double check valve next to the ARC valve and through a double check valve next to the brake switches. Pulling the retarder lever turns ON the retarder dash lamp, the brake lights, and changes the transmission shift points and anti-hunt timer. Air also flows from the retarder valve through a double check valve to the service and manual retarder brake relay valve. Only the rear brakes are ENGAGED when the retarder is ENGAGED. When the ARC is energized, air flows through two double check valves. Air flows from the ARC valve through a double check valve next to the ARC valve and through a double check valve next to the brake switches. Energizing the ARC turns ON the retarder dash lamp, the brake lights, and changes the transmission shift points and anti-hunt timer. Air also flows from the ARC valve to the ARC relay valve. The ARC relay valve opens and allows air from the service brake reservoirs to flow through a double check valve to the rear brake cylinder. Only the rear brakes are ENGAGED when the ARC is energized.
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BRAKE COOLING SYSTEM HOIST VALVE
MAKEUP TANK
OIL COOLER
OIL COOLING RELIEF VALVE
BRAKE RETRACTION PUMP
HOIST PUMP
BRAKE RETRACTION FILTERS
BRAKE RETRACTION VALVE TO PARKING BRAKES
HYDRAULIC TANK
REAR BRAKES
75 ¥ Brake oil cooling system - uses two pumps
This schematic shows the flow of oil through the brake cooling system. Two pumps provide oil for brake cooling; the hoist pump and the brake retraction pump. Both pumps pull oil from the hydraulic tank through a suction screen.
¥ Hoist pump oil flow
Oil flows from the hoist pump to the hoist valve. When the hoist valve is in the HOLD or FLOAT positions, all of the hoist pump oil flows through the oil cooler screen and the oil cooler to the rear brakes. Oil from the rear brakes flows through a return screen to the hydraulic tank.
¥ Brake retraction pump oil flow
Oil flows from the brake retraction pump through the brake retraction filters to the brake retraction valve. The brake retraction valve controls the oil pressure to release the parking brakes and shift the directional spool in the hoist valve. These functions require very little oil flow. Most of the oil from the brake retraction pump flows through the brake retraction valve and joins with the hoist pump oil to cool the brakes.
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¥ Brake cylinder oil makeup tank
Brake cooling oil also flows to the brake cylinder oil makeup tank. The makeup tank provides a continuos supply of oil to the brake cylinders. The brake cylinders require more oil as the brakes wear.
¥ Oil cooling relief valve
The pressure in the brake cooling system is controlled by a relief valve located in the hoist valve. The setting of the brake oil cooling relief valve is 586 ± 14 kPa (85 ± 2 psi). The relief valve is usually only needed when the brake cooling oil is cold. When brake cooling oil is at operating temperature, measured brake cooling oil pressure is usually much lower than the setting of the oil cooling relief valve.
¥ High brake cooling oil temperature
A brake oil temperature sensor is located in the brake oil cooling tube on the right side of the truck. The brake oil temperature sensor provides input signals to the Caterpillar Monitoring System or the VIMS which keeps the operator informed of the brake cooling oil temperature.
- Too high a gear - Engine speed too low
The most common cause of high brake cooling oil temperature is operating a truck in too high a gear for the grade and not maintaining a high enough engine speed. Engine speed should be kept at approximately 2230 rpm during long downhill hauls.
- Relief valve stuck open
If brake cooling oil temperature is high and flow to the brake cylinder oil makeup tank is low, make sure the oil cooling relief valve is not stuck open.
- Slack adjuster pistons stuck
Also, make sure the pistons in the slack adjuster are not stuck and holding too much pressure on the brakes (see Slides No. 147 - 149).
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INTEGRATED BRAKE CONTROL ELECTRICAL SYSTEM
INPUT COMPONENTS SHIFT LEVER SENSOR
THROTTLE SENSOR
TRANSMISSION OUTPUT SPEED SENSOR
ACTUAL GEAR SWITCH
ENGINE SPEED/TIMING SENSOR
SERVICE/RETARDER BRAKE SWITCH
PARKING/SECONDARY BRAKE SWITCH
OUTPUT COMPONENTS
ELECTRONIC SERVICE TOOL ENGINE CONTROL TRANSMISSION AND CHASSIS CONTROL (EPTC III)
CAT DATA LINK
ENGINE OUTPUT SPEED SENSOR
°C kPaMiles KM RPM Liter SERV CODE X10
MESSAGE CENTER MODULE
. ..
CAT DATA LINK
ON INPUT ARC ON/OFF SWITCH
ARC SUPPLY SOLENOID
OFF INPUT RETARDER PRESSURE SWITCH
ARC CONTROL SOLENOID
AUTO RETARDER PRESSURE SWITCH
RETARDER ENGAGED LAMP
ARC TCS
TCS ENGAGED LAMP
TCS TEST SWITCH
ARC TCS TCS SELECTOR SOLENOID LEFT AND RIGHT
LEFT WHEEL SPEED SENSOR PROPORTIONAL SOLENOID
RIGHT WHEEL SPEED SENSOR
76 INTEGRATED BRAKE CONTROL (IBC) ¥ Integrated Brake Control (IBC)
The D-series update trucks use a new electronic control module for controlling both the Automatic Retarder Control (ARC) and the Traction Control System (TCS). There are three possible arrangements that can be installed on a truck. The three arrangements are: - ARC only - TCS only - ARC and TCS--called IBC When a truck has both the ARC and the TCS, the arrangement will be referred to as the Integrated Brake Control (IBC) system.
¥ Flash files required
Each arrangement requires a separate "flash" file to tell the control which arrangement is installed. Therefore, there are three separate flash file part numbers, and which flash file is used depends on the hardware installed on the truck.
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¥ Brake functions controlled by electrical signals
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The IBC receives information from various input components such as the Engine Output Speed (EOS) sensor, retarder pressure switch, left and right wheel speed sensors and the TCS test switch. Based on the input information, the IBC determines whether the service/retarder brakes should ENGAGE for the ARC or the parking/secondary brakes should ENGAGE for the TCS. These actions are accomplished by sending signals to various output components. Output components include the ARC supply and control solenoids, the retarder ENGAGED lamp, the TCS selector and proportional solenoids and the TCS ENGAGED lamp. The IBC also provides the service technician with enhanced diagnostic capabilities through the use of onboard memory, which stores possible diagnostic codes for retrieval at the time of service.
¥ Benefits of electronic communication
The Advanced Diesel Engine Management (ADEM II) engine control, the Transmission and Chassis control, the Caterpillar Monitoring System or the Vital Information Management System (VIMS) and the IBC all communicate with each other through the CAT Data Link. Communication between the electronic controls allows the sensors of each system to be shared.
¥ Service tool diagnostic and programming functions
The Electronic Control Analyzer Programmer (ECAP) and the Electronic Technician (ET) Service Tools can be used to perform several diagnostic and programming functions (see Slide No. 23). Some of the diagnostic and programming functions that the service tools can perform are: - Display real time status of input and output parameters - Display the internal clock hour reading. - Display the number of occurrences and the hour reading of the first and last occurrence for each logged diagnostic code and event. - Display the definition for each logged diagnostic code and event. - Display the supply and control solenoid engagement counter. - Program the ARC control speed - Perform ARC diagnostic tests - Upload new Flash files
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77
¥ Integrated brake control (arrow) ¥ MAC14 style control - No diagnostic window - Diagnostics and programming requires ECAP or ET
¥ MAC14 looks like ADEM II
The Integrated Brake Control (IBC) (arrow) is located in the compartment at the rear of the cab. The new control is a MAC14 style electronic control, which means that it is a Multiple Application Control capable of 14 outputs (MAC14). The MAC14 does not have a diagnostic window like the ARC and the TCS used on the D-series pre-update trucks. Diagnostic and programming functions must all be done with an Electronic Control Analyzer Programmer (ECAP) or a laptop computer with the Electronic Technician (ET) software installed. ET is the tool of choice because the MAC14's can be reprogrammed with a "flash" file using the Winflash application of ET. ECAP cannot upload "flash" files. MAC14's look like the second generation Advanced Diesel Engine Management (ADEM II) electronic control with two 40-pin connectors, but MAC14's do not have fittings for cooling fluid. Also, there is no access plate for a personality module.
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AUTOMATIC RETARDER CONTROL INTEGRATED BRAKE CONTROL (ARC) (TCS)
ENGINE SPEED SENSOR ON INPUT ARC ON/OFF SWITCH OFF INPUT SERVICE TOOL ENGINE CONTROL EPTC III MESSAGE CENTER
CAT DATA LINK RETARDER ENGAGED LAMP
SUPPLY SOLENOID VENT
AIR FROM SERVICE BRAKE RESERVOIR
VENT CONTROL SOLENOID
SERVICE BRAKE VALVE
TO SERVICE/ RETARDER BRAKE RELAY VALVE
AUTOMATIC RETARDER VALVE
MANUAL RETARDER VALVE
AUTO RETARDER PRESSURE SWITCH
RETARDER PRESSURE SWITCH
TO ARC RELAY VALVE
78 Automatic Retarder Control (ARC) ¥ Automatic Retarder Control (ARC)
The Automatic Retarder Control (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/retarder brakes. If the ON/OFF switch is moved to the ON position, the ARC 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 not connected to the service brakes and the manual retarder. When the ARC is engaged, air flows from the ARC valve to a separate relay valve located near the brake master cylinders (see Slide No. 69).
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¥ ARC set to maintain 2230 engine rpm
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The ARC is set at the factory to maintain a constant engine speed of 2230 ± 50 rpm (engine speed setting is programmable). 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. For proper operation of the ARC, the operator needs only to activate the control with the ARC ON/OFF switch and select the correct gear for the grade, load, and ground conditions. The ARC 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 2300 rpm, the ARC will apply the retarder as needed to maintain a constant engine speed.
¥ ARC provides engine overspeed protection
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 ON/OFF switch is in the OFF position and the throttle is depressed. Trucks approaching an overspeed condition will sound a horn and activate a light at 2475 rpm. If the operator ignores the light and horn, the ARC will engage the retarder at 2560 rpm. If the engine speed continues to increase, the transmission and chassis control 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) at 2675 rpm.
¥ ARC provides programming and diagnostic capability
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. By using an ECAP or a laptop computer with the Electronic Technician (ET) software installed, service personnel can access the stored diagnostic information or set the adjustable engine speed control setting. The Auto Retarder Control receives signals from several switches and sensors. The control analyzes the various input signals and sends signals to the output components. The output components are two solenoids and a lamp.
INSTRUCTOR NOTE: For more detailed information about the Automatic Retarder Control (ARC) system, refer to the Service Manual Module "Automatic Retarder Control System" (Form SENR5683) and the Technical Instruction Module "Automatic Retarder Control System" (Form SEGV2593).
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1. Retarder pressure switch
Shown is the location of the retarder pressure switch (1). The retarder pressure switch signals the control module when retarder air pressure is present (manual or automatic). The switch is normally open and closes when the manual retarder or automatic retarder is engaged. A fault is recorded when the control module detects the absence of retarder pressure (switch open) while the supply solenoid and the control solenoid are energized.
2. Auto retarder pressure switch 3. Automatic retarder valve
The auto retarder pressure switch (2) signals the control module when air pressure is present and the automatic retarder valve (3) is functioning. The auto retarder pressure switch is located in front of the cab in the output port of the automatic retarder valve. The switch is normally closed and opens only when the auto retarder is engaged. A fault is recorded when the control module detects the presence of auto retarder pressure (switch open) while the supply solenoid and the control solenoid are not energized.
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4. Supply solenoid valve
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The supply solenoid valve (4) turns ON or OFF to control the flow of supply air to the automatic retarder valve (3). The control module energizes the supply solenoid valve with + Battery voltage (24 Volts) at 2125 rpm. The supply solenoid is energized approximately 100 rpm less than the programmed control speed setting. A fault is recorded if the control module senses the signal to the supply solenoid as open, shorted to ground, or shorted to battery.
5. Control solenoid valve
The control solenoid valve (5) modulates the air flow to the brakes during automatic retarding. The control solenoid receives a Pulse Width Modulated (PWM) signal from the control module. The longer the duty cycle, the more time the control solenoid valve is open and more air pressure is allowed to the brakes. Voltage to the control solenoid increases proportionally from 0 to approximately 22 Volts with the demand for more brake pressure. A fault is recorded if the control module senses the signal to the control solenoid as open, shorted to ground, or shorted to battery.
¥ Supply and control solenoid resistance
Normal resistance through the supply and control solenoids is 31 Ohms. An excess resistance of approximately 40 Ohms will prevent the valves from opening and will cause a supply or control valve malfunction fault to be logged. Therefore, a measurement of approximately 71 Ohms or more will show that the solenoid is defective.
¥ ARC valve malfunction
The control module can also determine if the solenoid valves have malfunctioned (valves leaking). If air pressure is present at the auto retarder pressure switch when the solenoids are not energized, the auto retarder pressure switch will signal the control module that the ARC valve has malfunctioned.
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TRACTION CONTROL SYSTEM INTEGRATED BRAKE CONTROL (ARC) (TCS) ELECTRONIC SERVICE TOOL TCS ENGAGED LAMP
SERVICE/RETARDER BRAKE SWITCH TRANSMISSION OUTPUT SPEED SENSOR
TCS SELECTOR SOLENOID LEFT AND RIGHT
CAT DATA LINK
TCS TEST SWITCH PROPORTIONAL SOLENOID
LEFT WHEEL SPEED SENSOR
+ 10V TO WHEEL SENSORS
RIGHT WHEEL SPEED SENSOR
80 Traction Control System (TCS) ¥ TCS uses parking/secondary brakes
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 system is controlled by the TCS or Integrated Brake Control (IBC) (see Slide No. 77). The TCS electronic control monitors the drive wheels through three input signals: one at each drive axle, and one at the transmission output shaft. When a spinning drive wheel is detected, the electronic control sends a signal to the selector and proportional valves which in turn 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 electronic control sends a signal to release the brake.
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¥ TCS formally called AETA
The TCS was formerly referred to as the Automatic Electronic Traction Aid (AETA). The operation of the system has not changed. The main difference is the appearance of the electronic control and the TCS is now on the CAT Data Link. Also, the ECAP and ET Service Tools can communicate with the TCS.
¥ Service/retarder brake switch
A service/retarder brake switch provides an input signal to the TCS through the CAT Data Link and performs two functions (see Slide No. 43):
- Stops TCS function - Performs diagnostic test
1. When the service brakes or retarder are ENGAGED, the TCS function is stopped. 2. The service/retarder brake 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. NOTE: During the diagnostic test, the parking/secondary brakes must be released.
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CONCLUSION This presentation has provided a basic introduction to the Caterpillar 769D/771D/773D/775D UPDATE 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 serviceman to analyze problems in any of the major systems on these trucks.
UPDATE 97 9/98
Printed in U.S.A.
