Should i change Transmission Fluid Change and Axle Fluid?
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Drivetrain - Rear Axle Lubricant Compatibility & Usage
File in Section: 04 - Driveline Axle
Bulletin No.: 99-04-20-001
Date: June, 1999
INFORMATION
Subject:
Rear Axle Lubricant Compatibility and Usage
Models:
1999 Cadillac Escalade
1988-99 Chevrolet and GMC C/K, G Van and P1-3 Series Models
Built after the VIN Breakpoints (C/K) listed.
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 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.
---------- Post added at 08:54 PM ---------- Previous post was at 08:46 PM ----------
So in the transfer case I use synthetic and the rear convetional?
File in Section: 04 - Driveline Axle
Bulletin No.: 99-04-20-001
Date: June, 1999
INFORMATION
Subject:
Rear Axle Lubricant Compatibility and Usage
Models:
1999 Cadillac Escalade
1988-99 Chevrolet and GMC C/K, G Van and P1-3 Series Models
Built after the VIN Breakpoints (C/K) listed.
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 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.
---------- Post added at 08:54 PM ---------- Previous post was at 08:46 PM ----------
So in the transfer case I use synthetic and the rear convetional?
Last edited:
SunlitComet
OBS Jedi-Do Good
front axle:
Grade Synthetic
Viscosity 75W-90
Transfer case:
NVG 246-NP8 Automatic Transfer Case Fluid GM Part No. 12378508
GM Performance Parts Auto Trak II transfer case fluid available from summit or dealer at least.
Rear according to TSB you posted and depending on your vin breakdown:
your rear 8.25 may be able to use: SAE 75W-90 Synthetic Axle Lubricant if not GL5 80-90w
---------- Post added at 11:45 PM ---------- Previous post was at 11:34 PM ----------
Basically if you have to use rtv then it probably wont work it seems.
Grade Synthetic
Viscosity 75W-90
Transfer case:
NVG 246-NP8 Automatic Transfer Case Fluid GM Part No. 12378508
GM Performance Parts Auto Trak II transfer case fluid available from summit or dealer at least.
Rear according to TSB you posted and depending on your vin breakdown:
your rear 8.25 may be able to use: SAE 75W-90 Synthetic Axle Lubricant if not GL5 80-90w
---------- Post added at 11:45 PM ---------- Previous post was at 11:34 PM ----------
Basically if you have to use rtv then it probably wont work it seems.
Last edited:
yeah - that was the feeling i received from reading the bulletin.
Are you familiar with the RTV vs gasket? I'm assuming the rear housing is the same, its just the rubber they used to seal it...correct assumption?
Irregardless of what's on the rear now, if I use a gasket on the rear when i service it, I believe i should be ok.
What do you think?
Are you familiar with the RTV vs gasket? I'm assuming the rear housing is the same, its just the rubber they used to seal it...correct assumption?
Irregardless of what's on the rear now, if I use a gasket on the rear when i service it, I believe i should be ok.
What do you think?
SunlitComet
OBS Jedi-Do Good
some part pictures for your truck seem to show a molded gasket for the front but still shows a paper gasket for which you will still need some gasket sealer so if if the sealer is prone to breakdown the it may not work. I would still chance it and try it out. Better yet look at aftermarket rear covers that may use a molded gasket. Personally don't know why some things were done with rtv or paper gasket with sealer. Cost maybe. The housing would be the same but the cover would be designed to accommodate the molded gasket like aftermarket cover. Going to do on my self one day. Cast with a sight glass if possible. Maybe even a temperature probe too.
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