A/T - 4L60 No Reverse/Delayed Reverse

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GMC NUMBER: 91-7A-181

GROUP: 7A Automatic Transmission

DATE: March 1992

CORPORATE
NUMBER: 277111


SUBJECT:
NO REVERSE/DELAYED REVERSE COLD (INSTALL LONG LIPPED REVERSE INPUT CLUTCH PISTON OUTER SEAL)

MODELS:
1989-91 S/T, C/K, R/V, AND P TRUCKS, M/L AND G VANS WITH 4L60 AUTOMATIC TRANSMISSIONS


Some 1989-1991 HYDRA-MATIC 4L60 (THM 700-R4) transmissions may exhibit a "no reverse" or "delayed reverse" condition when outside temperatures are below zero degrees Fahrenheit.

SERVICE PROCEDURE:
A transmission is considered to have a delayed reverse condition if it takes longer than three seconds for the transmission to engage when shifted into the reverse range.





If a transmission has a "no reverse" or "delayed reverse" condition, inspect the reverse input clutch piston outer seal. Determine if the seal is a "short lip" or "long lip" design by comparing it to Figure 1. If it is a short lip design, replace it with a long lip seal contained in the service packages listed under Service Parts Information.


If the reverse input clutch piston outer seal is a long lip design, or the newly installed long lip seal doesn't alleviate the delayed reverse condition, the reverse input clutch housing may be out of round. Inspect the housing and replace if necessary.

Refer to the HYDRA-MATIC 4L60 Automatic Transmission Section of the appropriate year Light Duty Unit Repair Manual for instructions on installing the reverse input clutch seals.

SERVICE PARTS INFORMATION:
The long lipped seals are available in several service packages.

Part
Description Number
Pkg - Overhaul Seals and Gaskets 8683958
Pkg - Overhaul Repair Complete 8683959

Parts are currently available at GMSPO.