A/T - No Reverse or Slipping in Reverse

Bulletin Number:
93-7-3

Reference Number:
277143

Publish Date:
10/92



Subject:
NO REVERSE OR SLIPPING IN REVERSE (INSTALL NEW RETURN SPRING AND SPIRAL RETAINING RING)

Models
Affected:
1992-93 SUNBIRD, GRAND AM, LEMANS, GRAND PRIX AND TRANS SPORT MODELS


TRANSMISSION APPLICATIONS:
1992-93 HYDRA-MATIC 3T40 (MD9)(THM 125-C)

TRANSMISSION MODELS:
All



CONDITION:

Some 1992-1993 HYDRA-MATIC 3T40 transaxles in Sunbird, Grand Am, LeMans, Grand Prix and Trans Sport models may slip in reverse, or have no reverse gear.

CAUSE:

Internal fluid leaks in the lo and reverse clutch circuit can cause the lo and reverse clutch piston to partially apply when the transaxle is in a drive gear. The current return spring load may not be great enough to keep the piston from partially applying.

CORRECTION:

Replace the lo and reverse clutch return spring, spring retainer and snap ring with a new design clutch belleville return spring and spiral retaining ring. The new clutch return spring has a higher spring rate to keep the piston from partially applying.

SERVICE INFORMATION:





1993 HYDRA-MATIC 3T40 transaxles built beginning July 1, 1992 (Julian Date 182) already contain the new design return spring and spiral retaining ring.

The new return spring and spiral retaining ring can be used to service any 1992-1993 HYDRA-MATIC 3T40 (previously THM 125-C) transaxle.



NOTICE:
Do not install the new design return spring in 1991 or previous HYDRA-MATIC 3T40 transaxles. These models have not had their hydraulic pressures re-calibrated to accept the new spring with a higher spring rate. Transaxle damage will result if this new return spring is installed in 1991 or previous HYDRA-MATIC 3T40 models.

If the previous design return spring and retainer is being replaced with the new design, install the lo blow off line-up from the service package into the transaxle when the return spring is changed.

No change was made to the piston or housing.





The lo and reverse clutch spring retainer (656) was eliminated in the design change.

SERVICE PARTS INFORMATION:

Parts are currently available from GMSPO.

Part Number Part Name





8687998 Repair Kit -- Lo/rev Belleville Spring
and Retainer (includes new
belleville return spring (655),
new spiral retaining ring (657),
lo blow off spring and plug
(325) and lo blow off valve plug
(326))

SERVICE MANUAL REFERENCE:





Refer to the HYDRA-MATIC 3T40 Automatic Transaxle Unit Repair Section of the appropriate Service Manual for instructions on servicing the lo/reverse clutch. Figure 3 of this bulletin shows the installation orientation of the new belleville return spring and spiral retaining ring.