NOISY TRANSFER CASE IN 4-HIGH PROCEDURE & PARTS UPDATE

SUBJECT: NOISY TRANSFER CASE IN 4-HIGH (SERVICE PROCEDURE AND PARTS UPDATE)

VEHICLES AFFECTED: 1988-91 'T' TRUCKS WITH 231HD TRANSFER CASE

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 CANSPO.

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.