Info - Rear Axle Lubricant Compatibility and Usage #99-04-20-001 - (06/18/1999)
Rear Axle Lubricant Compatibility and Usage
1988-99 Chevrolet and GMC C/K, G Van and P1-3 Series Models
1999 Cadillac Escalade
Built after the VIN Breakpoints (C/K) listed below:
This bulletin is being revised to add the 1999 Model Year, VIN Breakpoint information, and additional text. Please discard Corporate Bulletin Number 86-42-04 (Section 4 - Driveline/Axle).
This bulletin is being issued to inform dealers about the compatibility and usage of the new Fuel Efficient SAE 75W-90 Synthetic Axle Lubricant, GM P/N 12378261 (In Canada use P/N 10953455), with current axles, and with the non-synthetic axle lubricant, GM P/N 1052271 (In Canada use P/N 10950849), for the rear axles on the above light-duty trucks.
Testing has shown that the new synthetic lubricant will chemically attack the Room Temperature Vulcanizing (RTV) sealant. Use only the non-synthetic lubricant, P/N 1052271, in axles using RTV sealant (See 9.5 and 10.5 information below).
American Axle and Manufacturing (A.A.M.) has approved the use of the new Fuel Efficient SAE 75W-90 synthetic axle lubricant for rear axles with the following restrictions:
All 8.6 inch axles are compatible as originally built.
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 HD3500 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
P/N
Description
Quantity
327739
Gasket, Axle Shaft Seal
1
12378261
(In Canada use P/N 10953455)
Fuel Efficient SAE 75W-90 Synthetic Axle Lubricant
1
1052271
(In Canada use P/N 10950849)
Non-Synthetic Lubricant
1
12471310
Kit, 9.5 Inch Axle Cover Pan
1
