SLIPS IN 1ST AND/OR NO 1ST GEAR/NEW PISTON SEALS

MODELS AFFECTED: 1980-1989 3T40 (THM125C) TRANSAXLES

BULLETIN COVERS

New Forward Clutch Piston Seals (626, 627) made of Viton. These new Viton seals replace the currently used lip seals which may become brittle and take a permanent heat set (become flat) with high mileage, allowing possible leaks in the forward clutch (624). Refer to Figure 1.

DATE OF PRODUCTION CHANGE

Viton seals went into production for all Willow Run built Hydra-matic 3T40 (THM125C) transaxles October 6, 1989 (Julian Date 279).

SERVICE PROCEDURE

This new Viton seal can be used on all model year Hydra-matic 3T40 (THM125C) transaxles.

SERVICE PARTS INFORMATION

Refer to the following part number when ordering new Viton seals to service the forward clutch assembly.

Part Number Description

8631986 Piston Seals (Viton), Forward Clutch

Current packages will be revised to contain new Viton seals. Parts are currently available from GMSPO.

SERVICE MANUAL REFERENCE

Refer to the Hydra-matic 3T40 (THM125C) (MD9) Automatic Transaxle Unit repair section of your service manual whenever service of the forward clutch is necessary.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.