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Number: 91-370-0B
Section: 0B
Date: JULY 1991
Corporate Bulletin No.: 964201R
Subject: LOCKING DIFFERENTIAL LUBRICANT
Model and Year: 1982-91 ALL TRUCKS WITH G80 REAR AXLE
THIS BULLETIN CANCELS AND SUPERSEDES DEALER SERVICE BULLETIN NO.
90-139-4A, DATED JANUARY 1990. CONDITION DESCRIPTION AND CORRECTION
HAVE BEEN ADDED AS WELL AS THE 1991 MODEL YEAR. ALL COPIES OF 90-139-4A
SHOULD BE DISCARDED.
Some light duty trucks equipped with locking rear axles (G80) may exhibit rear axle chatter,
especially when turning a corner from a stop.
This condition of alternate engagement and disengagement of the clutches in the
differential assembly is usually caused by contaminated axle lubricant.
To correct this condition, drain and refill the rear axle with SAE 80W-90 GL5 (P/N 1052271).
The use of any additive in locking rear axles (G80) is not recommended. Rear axle additives
are designed for use in limited slip differentials which are normally installed in cars. All
ght duty trucks equipped with RPO G80 make use of a locking differential and the use of
additives will delay the engagement of the locking mechanism and may decrease axle life.
VEHICLES/COMPONENTS INVOLVED:
Some light duty trucks equipped with locking rear axles, RPO G80.
SERVICE PARTS INFORMATION:
Part Number Description
1052271 Lubricant, Rear Axle (24 oz.)
See Appropriate Parts Manual Gasket, Rear Axle Housing Cover
available throu GMSPO.