K 2500 Truck 4WD V8-379 6.2L DSL VIN C FI (1989)
^
9.5 inch axles on vehicles built prior to mid-February 1998 are NOT compatible because RTV sealant is used on the cover pans.
On vehicles built after mid-February 1998 and equipped with 9.5 inch rear axles, synthetic lubricant, P/N 12378261, can be used because the RTV
was replaced with a gasket. Other mid-February changes to the 9.5 inch rear axles include a new cover pan and cover pan fasteners common to other
axles.
Important:
The new cover pan is not retrofittable to the housing of 9.5 inch axles on vehicles built prior to mid-February 1998. A new retrofit kit is available that
will enable the use of synthetic lubricant for vehicles built after mid-February, 1998.
^
All 10.5 inch axles prior to March 3, 1999 are compatible if the axle shaft hub seal (RTV) is replaced with P/N 327739 gasket when changing to
synthetic lubricant.
As a product improvement, this new lubricant has been released into 1999 current production C/K vehicles built after the above VIN breakpoints (Except
HD3SOO models which use 75W-140 synthetic lubricant, P/N 12346140).
It is recommended that synthetic lubricant be used when changing rear axle lubricant for the following reasons:
^
Potential fuel economy
^
Lower operating temperature under severe usage conditions
Important:
^
You do not need to wash/rinse any non-synthetic lubricant from the axle cavity when changing over to a synthetic lubricant. However, you should
remove debris from the magnet and the bottom of the axle cavity whenever the axle fluid is changed.
^
On light-duty trucks equipped with locking differentials, do NOT use a limited-slip additive.
Parts Information
Parts are currently available from GMSPO.
