Diagnosis/Inspection

Proper diagnostic and inspection procedures must be followed when evaluating a suspect transaxle OD/REV clutch system failure and/or a low/reverse clutch piston retainer defect.

^ Check the fluid level and condition. Discolored or burnt fluid is an indication of transaxle overheating.

^ Connect the DRB II and perform the diagnostic tests as outlined in the appropriate Powertrain Diagnostic Procedure Manual. Be sure you complete the Shift Lever Test and the Clutch Test on 1990 models.

^ Record fault codes and clutch volumes.

Figure 1:

^ If the complaint is a "Stop Bump" condition go to the RPM display, road test the vehicle a sufficient distance to ensure the transaxle is warmed up. Observe the turbine RPM as the vehicle comes to a complete stop, the RPM should go to 0 RPM and stay there. If the turbine RPM rises close to engine RPM and then drops back to 0 RPM accompanied by the bump condition, this turbine RPM increase confirms the low/reverse clutch piston retainer seals are leaking. The transaxle must be removed and reconditioned. The low/reverse clutch piston retainer, seals and gasket must be replaced, Figure 1. Severe cases of "Stop Bump" will also initiate fault code # 39.
Perform the hydraulic pressure test if necessary as outlined in the appropriate Front Wheel Drive Service Manual, and record readings.

Figure 2:

If the results of your diagnosis indicate the transaxle must be removed for reconditioning, the following OD/REV clutch system components must be inspected to ensure the transaxle is correctly repaired:

^ OD/REV piston, excessive casting thickness in the area of the belleville return spring seat. Inspect the piston casting codes. If codes 55233 or letter code DP are found as shown in Figure 2, the piston casting thickness must be measured using a straight edge and six inch scale as shown in Figure
3. The measurement must be taken at the flat non-machined area just outboard of the belleville spring seat. If the measurement is 3/8 INCH OR LESS (9.5 mm) the piston must be replaced.

If the OD/REV piston is the four slot type, it must be replaced with OD/REV Piston, PN 4531492. If the OD/REV piston is the eight slot type it must be replaced with a four slot type Piston and Pressure Plate Package PN 5241063.

Figure 3:

^ OD/REV piston, casting thickness, measure the distance between the bottom of a straight edge and the non-machined area just outboard of the belleville spring seat as shown in Figure 3. If the measurement is 3/8 inch (9.5 mm) or less, replace piston.

Figure 4:

^ OD/REV piston outer lip seal, check for nicks or cuts, Figure 4.

Figure 5:

^ Input clutch hub outer lip seal, check for nicks or cuts, Figure 5.

Figure 6:

^ OD/REV piston, check for loose or missing orifice, Figure 6.
^ If the OD/REV piston orifice appears to be in the correct position it should be tested as follows:

1. Place a small dab of vaseline or petroleum jelly in the orifice hole inside the OD/REV piston.

2. Using a rubber tipped air blow gun apply a minimum of 30 psi of air pressure to the orifice hole inside the piston, the orifice must remain in place. If the orifice comes out of the piston hole, the OD/REV piston must be replaced.

^ If the OD/REV piston is the four slot type it must be replaced with OD/REV Piston, PN 4531492. If the OD/REV piston is the eight slot type it must be replaced with a four slot type Piston and Pressure Plate Package PN 5241063.



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