Hot Rod 1996–2000 Honda Civic Shift Feel Modifications
Civic by Mike Van Dyke
T
he Honda Civic has become a popular vehicle for modification by import performance enthusiasts. While the manual transaxle is usually the choice of the hardcore performance enthusiast, there are quite a few automatic-equipped Civic owners looking for “performance” shifts. If you do any high performance work at your shop, you’re likely to have an automatic-equipped Civic owner come in asking you about making the shifts firmer. In this issue, we’re going to go over a few simple modifications for firmer shifts and TCC apply on the A4RA / B4RA transaxle used in the 1996–2000 Civic. This article takes a conservative approach to making the shifts firmer. You want to be wary of making one of these units shift brutally hard, as its main weakness is the clutch drums. If you have the unit apart, check all the drums, specifically the first gear clutch drum. It’s common for this drum to crack right around the center, just outside the recess where the shaft nut is located (figure 1). Before we dive in…
If you’ve worked on many Honda
Figure 1
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Figure 2
Adjustment Plug Linear Solenoid Remove linear solenoid to adjust end plug transaxles, you already know that you have to remove and disassemble the transaxle to reach the valve body. Both you and your customer need to be keenly aware of this fact. Shift feel and firmness can be a subjective issue, and the only way to be certain your customer is going to be happy with the results is after the modifications have been performed. perfo rmed. The customer needs to understand that, if the unit has to come back out to fine tune shift feel, the labor isn’t free. With that said, a simple first approach is
to adjust shift feel without going inside the unit. This can be done by adjusting the linear solenoid, shown in figure 2. This adjustment is sensitive; it’s best to start with 1/8 to 1/4 turn clockwise, then road test to assess the results. Keep in mind that you’ll have to remove the solenoid to adjust it. Adjusting the linear solenoid is a simple modification and is easily reversible, but it has one major drawback: firmer shifts can be achieved up to a point, but too too much much adjustme adjustment nt can can have have negative effects on TCC control. That’s because the linear solenoi solenoid d isn’ isn’tt only used to control shift feel; it’s also used to control the torque converter clutch full apply timing. Cranking up the linear solenoid can lead to an abrupt TCC apply and lugging the engine, especially under light throttle acceleration. When you increase the linear solenoid pressure, instead of having partial part ial TCC apply at light thrott throttle, le, it
GEARS May/June 2006
Hot Rod Civic
Figure 3
CPC Valve Lineup
CPC Valve Spring
Secondary Valve Body Always Remove CPC valve for cleaning and to check for broken spring can go straight to full apply as soon as TCC is enabled. When this happens the engine will lug down, the dashboard will rattle, and acceleration will be poor until vehicle speed increas es, or until you press down far enough on the throttle for the PCM to command the TCC to release. After adjusting the linear solenoid, be sure to drive the vehicle at light to medium throttle to see if there are any negative effects on torque converter clutch operation.
Let’s Dive In!
To get even firmer shifts without TCC side effects, or to modify TCC apply, we have to go inside the unit. There are a couple of ways to approach modifying shift feel: accumulator springs, increase line pressure, etc. The easiest and most effective modification I’ve found is to simply adjust the CPC (Clutch Pressure Control) valve in the secondary valve body. (figure 3). The CPC valve is controlled by linear solenoid pressure, but the benefit here is adjusting the CPC
valve won’t affect TCC control. It’s very common for the CPC valve spring to break, so you’ll want to remove it for inspection. You’ll need a 5 mm hex key wrench and a 10 mm box end wrench to adjust or remove the CPC valve (figure 4): • Hold the 5 mm hex key wrench and loosen and remove the 10 mm lock bolt. • Measure and record the depth of the adjustment plug so it can be reassembled to the same position.
Figure 4
10mm Box End Wrench 5mm Hex Key Wrench Hold the adjustment plug with 5mm hex key and loosen lock bolt with 10mm box end wrench 28
Measure and record adjustment plug depth before disassembly GEARS May/June 2006
Figure 5
Lock-Up Valve Body Spacer Plate
Turning in the CPC valve adjustment an additional 1/8 to 1/4 turn clockwise will provide moderately firmer shifts.
TCC Release Orifice
Enlarge to 0.100”
TCC modification: Drill TCC release orifice to 0.100” The CPC valve spring isn’t available separately from Honda; you must purchase the complete secondary valve body. A replacement spring is available from Sonnax, part number 88894X. The Sonnax spring is a little different from the OEM, so be sure to follow their installation and adjustment
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procedures. Turning in the CPC valve adjustment an additional 1/8 to 1/4 turn clockwise will provide moderately firmer shifts. 1/2 turn to 1 turn clockwise will create very firm shifts. Blocking the valve inboard will get you into the 1–2 chirp zone. Keep
Features include: The industry's first, ever, 12 individually controlled completely negative outputs reprogrammable 12 individually controlled handheld ransmission controller positive outputs for the later multi-stage Eight switch indicator lights solenoid sequencing units is almost here.
The new Schaffer Programmable Controller will not replace the Schaffer Shifter, it will be programmed for units that the Schaffer Shifter cannot control.
Keep your eyes open for the new programmable controller to be released in April 2006!
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Hot Rod Civic
Figure 6
Torque Converter Check Valve
Install 0.150” Shim Valve in first, Spring on top
Lock Up Control Valve
Install 0.200” Shim
Regulator Valve Body
TCC modification: Shim the lock up control valve spring 0.200” and shim the torque converter check valve spring 0.150” in mind that turning up the CPC adjustment will also make the engagements firmer. TCC Modifications
1. 2.
Enlarge the TCC release exhaust orifice to 0.100” (figure 5). Increase the spring pressure about 40% on the LockUp Control Valve (figure 6) by shimming the spring about 0.200”. This can be accomplished by dropping a G4AEL valve body orifice cup or some washers inside the valve in the spring pocket. To check the spring pressure on a scale, push the valve down over
the spring until just before the end of the valve touches the scale: It should have about 2 pounds of spring pressure. 3. Increase the spring pressure on the Torque Converter Check Valve (figure 6) by 30% by dropping some washers inside of the torque converter check valve to shim up the spring about 0.150”. That just about wraps up our fun for this issue. Remember, don’t get too crazy with this unit… at least, not until someone starts making billet clutch drums!
Remember, don’t get too crazy with this unit… at least, not until someone starts making billet clutch drums!. 30
GEARS May/June 2006
