Driveline - Stop Clunk

91chevy11

GMC NUMBER: 91-4A-77

GROUP: 4A Propeller Shaft
DATE: March, 1991

CORPORATE
NUMBER: 964101R


SUBJECT:
DRIVELINE STOP CLUNK

MODELS:
1988-91 C1, C2 LIGHT DUTY TRUCKS WITH 4L60 AND 3L80 AUTOMATIC TRANSMISSIONS


THIS BULLETIN CANCELS AND REPLACES GMC TRUCK SERVICE BULLETIN 89-T-98 (CORPORATE NUMBER 964101) DATED AUGUST, 1989 TO ADD 1990-91 MODEL YEARS AND TO UPDATE THE PART NUMBER. ALL COPIES OF 89-T-98 SHOULD BE DISCARDED.

GMC TRUCK RECOMMENDS THAT A COPY OF THIS BULLETIN ALSO BE FILED UNDER SECTION 7A-AUTOMATIC TRANSMISSION.


Normal driveline tension build-up is released following vehicle braking on some 1988-91 C1 and C2 models (with single piece propshafts and automatic transmissions) as driveline clunk when stopping. The tension build-up is the result of the driveshaft splines binding on the transmission slip yoke.

To eliminate stop clunk due to spline-yoke bind, the driveshaft splines should be lubricated with a special lubricant. This bulletin releases a new lubricant that has increased durability over the previously released lubricant.

NOTICE: This procedure should be applied to 1988-91 C1, C2 vehicles with automatic transmissions and one-piece propshafts only. When applied to other vehicles, possible transmission lube contamination could result.

SERVICE PROCEDURE

1. Remove driveshaft.

2. Clean slip yoke and inside of driveshaft spline with solvent and clean cloth.


3. Apply grease (P/N 12345879) to slip yoke spline with a brush or swab, so as to completely cover the entire spline with a light coating of grease.

4. Reinstall propshaft.

SERVICE PARTS INFORMATION

Part Number Description
12345879 1 lb. can of special lubricant
(should service about 50 vehicles)

Parts are currently available from GMSPO.

WARRANTY INFORMATION

For vehicles repaired under warranty use:

Labor Operation: T7995

Labor Time: 0.4 hr

NOTE: Labor Operation is coded to base vehicle coverage in the warranty system.