GM 199x vehicles with RTV sealant for diff.

[Donald]

It seems some 199x GM vehicles (like my Suburban) used RTV sealant for the diff. depending upon the gear diameter (according to the Amsoil product selection guide). Never heard that mentioned here. Amsoil said to not use a synthetic gear oil if the diff. was sealed with RTV sealant. Rather than investigate if my front or rear diff was sealed with RTV is it simpler to just use a high quality regular gear oil?

 

[eljefino]

What's the worst that can happen? It'd leak?

Go for it. I know it's apples to oranges, but my engine is sealed up with RTV and I've run syn oil in that...

 

[Trav]

My Expedition was sealed with RTV and Ford specs synthetic fluid, go figure.
Go to your local Honda dealer and get a tube of the Grey Honda Bond,it cost about $8, very nice stuff and seals perfectly with synthetics.

 

[Chris142]

I've always used Ultra black or Ultra grey and never had a leak with dino or syn gear oils. Permatex does make a special sealant for Diffs though.

http://differentialgasket.pasundan.org/d...v-sealant-3-oz/

 

[mechtech2]

Use the best RTV you can get, and let it dry throughly. CLEAN the surfaces really nice, first.

 

[kschachn]

Yep, I used the Permatex 81182 on my BMW (and M1 gear oil) and so far it has worked great. The stuff gives directions for use with or without a gasket.

 

[Pablo]

I think GM just used some junky RTV. Just replace with a good RTV and fill with Amsoil gear oil.

 

[Donald]

But of all the lubricants in my Suburban, (engine oil, transmission, transfer case, F & R diffs., aren't the diffs the least needy of synthetic oil?

 

[Mike_dup1]

Fyi - This is not AMSOIL saying this, this is GM recommendations as somewhere I have these exact words in a GM bulletin.
Quote:
Do not use synthetic lubricant in axles using RTV sealant.
Synthetic lubricant will chemically attack RTV sealant.
American Axle has only approved the use of Synthetic
Lubricant 75W-90 GM part no. 12378261, as follows:
a. All 8.6 inch rear axles are compatible.
b. All 9.5 inch rear axles built before mid-February 1998
(RTV sealant used to seal cover pan) are not compatible
c. All 9.5 inch rear axles built after mid-February 1998
(equipped with cover pan & gasket) are compatible.
d. All 10.5 inch rear axles built prior to March 3, 1999 are
compatible if axle shafthub RTV sealer is replaced with GM
gasket part no. 327739.

 

[mechtech2]

^^ Why would you believe the part about sealers, but not about NOT changing the fluid??

Both wrong, IMO.

 

[Donald]

The vehicle in question is a 1993.

 

[Pablo]

Originally Posted By: Donald
But of all the lubricants in my Suburban, (engine oil, transmission, transfer case, F & R diffs., aren't the diffs the least needy of synthetic oil?


I would say completely the opposite is true.

Diffs get hot. Very hot. They are neglected. They have no filtration. The volume is small.

This is the place for synthetic oil.

 

[Steve S]

Differentials may or may not get hot tnough to need syn oil but syn gear oil is an especially good application for syn oils. Delo ESI is a GPII type gear oil that is almost as good as the best syn oils and better than the rest if you can find it close to where you live. You may be able to find a gasket for the diffs if you have a good parts store with a guy that knows more than it isn't in the computer. I found a gasket for my Wifes Powerstroke Ford p/u differential which is nicer than RTV. I have used RTV in diffs with Redline syn gear oil with out any problems.

 

[Steve S]

A late thought, probably most people do not keep their GMs long enough for GM to recommend oil changes

 

[JasonC]

Ive never had a problem using RTV sealant and Synthetic Gear Oil. I never use a gasket, just RTV.

 

[Stu_Rock]

Originally Posted By: Pablo
I think GM just used some junky RTV. Just replace with a good RTV and fill with Amsoil gear oil.
This is it.

My Chrysler 9.25 is sealed with RTV and it calls for synthetic for "severe service."

Like Steve S said, I have noticed that there are sometimes gaskets available for RTV applications (mine is one too). What do you guys think about these gaskets instead of RTV?

 

[kschachn]

Originally Posted By: Stu_Rock
Like Steve S said, I have noticed that there are sometimes gaskets available for RTV applications (mine is one too). What do you guys think about these gaskets instead of RTV?


For my BMW they (BMW) discontinued the gasket in favor of RTV. BMW specs a Loctite sealant, available at the dealer for $$ or elsewhere, but I used the Permatex stuff instead.

You can buy a Victor Reinz gasket similar to the old BMW gasket though. And the Permatex instructions tell you how to use the sealant with or without a gasket. I just went ahead and use it as directed without a gasket and it has worked fine.

 

[Donald]

OK, I am about to get this done. Vehicle is a 93 Suburban 4WD. A few choices:

1) Use synthetic and see what happens
2) Use regular and thus no worries
3) Pay extra to have the RTV replaced with better RTV and use synthetic.

Is Mobil 1 good enough or order Amsoil severe gear? I am not sure exactly how much I need via the Amsoil vehicle listing and can easily return extra Mobil 1.

Too cold and wet or snowy for me to do it myself.