Transfer Case - 231HD Noisy in 4WD High
90chevy27Number: 91-63-7D
Section: 7D
Date: August 1990
Corp. Bulletin No.: 067405
Subject: NOISY TRANSFER CASE IN 4-HIGH
Model and Year: 1988-91 T TRUCKS WITH 231HD TRANSFER CASE
TO: ALL CHEVROLET DEALERS
Some 1988-1991 T trucks may experience a noisy transfer case when the truck is in 4-high. The noise is caused by rotation of the chain and gears and is transmitted through the transfer case shift linkage into the body interior.
A quieter "T" pattern transfer case chain and softer durometer shift rod grommets have been released to decrease the noise level. The chain can be identified by two blue links while the previous design contained one blue link. The softer grommets are orange or beige while the previous design grommets were white.
SERVICE MANUAL REFERENCE
Refer to the Unit Repair Section of the appropriate Service Manual for the proper replacement procedures.
SERVICE PARTS INFORMATION
Quantity
Part Number Description Required
15635937 Chain 1
15659238 Shift Rod Grommet 2
Parts are currently available through GMSPO.
WARRANTY INFORMATION
For vehicles repaired under warranty use:
Labor Labor
Operation Description Time
T7036 Replace Chain and 2.1 hrs.
Install Grommets
FAILURE CODE: 92