K 2500 Truck 4WD V8-379 6.2L DSL VIN C FI (1989)
Clutch: All Technical Service Bulletins
A/T - 4L60 No Reverse/Delayed Reverse
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
