A/T - No 1st Gear/Slips In 1st Gear
89chevy34Number: 89-277-7A
Section: 7A
Date: November 1989
Corporate Bulletin No.: 977147
Subject: SLIPS IN 1ST AND/OR NO 1ST GEAR
Model and Year: 1980-89 A, J, L, T CARS WITH 3T40 (125C) AUTOMATIC TRANSMISSION
Figure 1:
TO: ALL CHEVROLET DEALERS
This 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 milage, allowing possible leaks in the forward clutch (624). Refer to Figure 1.
Viton seals went into production for all Willow Run built HYDRA-MATIC 3T40 (THM 125C) transaxles October 6, 1989 (Julian Date 279).
This new Viton seal can be used on all model year HYDRA-MATIC 3T40 (THM 125C) transaxles.
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.
Refer to the HYDRA-MATIC 3T40 (THM 125C) (MD9) Automatic Transaxle Unit repair section of your service manual whenever service of the Forward Clutch is necessary.