K 2500 Suburban 4WD V8-6.5L DSL Turbo VIN F (1996)
Fluid - Differential: All Technical Service Bulletins
Transfer Case - No 4 x 4 HI Range in Cold Weather
File In Section: 7 - Transmission
Bulletin No.: 66-74-07
Date: September, 1996
Subject:
Four Wheel Drive HI Range Does Not Engage During Cold Weather
(Replace Front Differentia Gear Lube)
Models:
1996-97 Chevrolet and GMC K1, K2 Models with Electric Shift Transfer Case (RPO NP1)
Condition
Some owners may report that if the ambient temperature is 10° F (-12° C) or colder, when attempting to shift the transfer case from 2HI to 4HI while the
truck is moving, the 2HI indicator light remains on and the 4HI light flashes for an extended period of time but 4HI does not engage.
Cause
High viscosity of the front axle gear lube when cold. This high viscosity delays or prevents the front propeller shaft from rotating at the speed required
for front axle engagement.
Correction
Replace the front differential gear lube with SAE 75W-90 synthetic gear lube (P/N 12345836). Synthetic gear lube has a lower viscosity than
non-synthetic in cold weather conditions.
Service Procedure
Before installing the Synthetic Gear Lube, drain and refill the differential with fresh non-synthetic gear lube and drive the truck no less than 3 miles.
Then drain the differential and refill it to the level of the oil fill hole with the specified synthetic gear lube. This is necessary to ensure that the differential
is clean before adding the synthetic gear lube. Front differential gear lube capacity is as follows:
^
8-1/4 inch axle 1.6 liters (1.75 qt.)
^
9-1/4 inch axle 2.1 liters (2.2 qt.)
Part Information
P/N
Description
SAE 75W-90 Synthetic Gear Lube,
12345836
1 qt bottle
Parts are currently available from GMSPO.
Warranty Information
For vehicles repaired under warranty, use:
Labor
Labor
Operation
Description
Time
F 2022
Front Differential, Oil
0.6 hr
Important:
Labor operation is coded to base vehicle coverage in the warranty system. Zone Representative approval may be required for duplicate labor
operation.