Sealing Differential

[Scott Amann]

What product - specific names please - is the best sealer when re-assembling the third member to the housing? I have heard that regular silicon can "disolve" over time? Are there any "tricks of the trade" when putting this back together that would get it right the first time?

Any help is appreciated.

 

[gjz30075]

I've had excellent results using Permatex Ultra Gray. A thin film on the housing, then the gasket, and then a thin film on the gasket. I don't use the copper washers.

 

[downpiped]

I just sealed my versailles 9 in. with honda bond, or yama bond. Both are gasket makers/sealers. IMO they are better than RTV.

 

[Scott Amann]

Gasket - that brings up another question. When I pulled it out, there was not a gasket between the 3rd member and housing - just the sealer. I have been told that the gasket doesnt have to be used. I have had my car for 20 years and never had a leak untill I broke the seal a week ago. Thoughts on the gasket?

 

[xoxbxfx]

Gasket - that brings up another question. When I pulled it out, there was not a gasket between the 3rd member and housing - just the sealer. I have been told that the gasket doesnt have to be used. I have had my car for 20 years and never had a leak untill I broke the seal a week ago. Thoughts on the gasket?

I have seen many shops just use RTV black with no gasket. If the surfaces are smooth, you need a very thin film of it and you should be good to go. 1/8"-1/16" or so of RTV and done.

 

[68RCodeConv]

The copper washers are used to seal around the studs. Because the studs project into the housing it is possible for them to leak even when using a gasket and/or silicone.

 

[RUSTYNUT]

The copper washers are a seal. Use new ones. I use Permatex #2 non hardening and the gasket. IMHO the third member sits deeper without the gasket and puts a small amount of miss alignment on the axles. A little thread sealer on filler and drain plugs help.

 

[88gt]

I just assembled mine with "The Right Stuff" gasket sealer. Not cheap, but it appears to do exactly as advertised.

I applied a thin coat of sealer, gasket, thin coat of sealer then the chunk. Tightened it all down with new lock nuts and copper washers.

Just need to get the rear buttoned up and disc brakes on and it'll roll again!!

 

[Scott Amann]

Fantastic Help/Advice - Thanks to all who repsonded.

 

[ratio411]

I use a gasket.

I have seen them done without a gasket, just RTV, but I'd rather just use a gasket. Costs about the same as a tube of RTV, and seals fine.

If you remove the chunk occaisionally, you will appreciate just being able to slide the gasket off, rather than spending an hour scraping RTV.

 

[66 Restomod]

I also used a small piece of teflon tape on the threads of the fill plug. Not sure it's required but seems to work fine.

 

[ultrastang]

I've seen 3rd members that had no gaskets (just RTV), but this is not the way they came from the factory. This means at some point, someone was into the rear end assembly and didn't replace the gasket at the time the 3rd member was re-installed.

I don't know how critical it is to have the gasket, but consider this; The position of the 3rd member is indexed off the machined face of the rear end housing. The gasket would not only serve the purpose of sealing the housing from oil leaks, but to a degree, it's also a shim.

Without a gasket, the 3rd member will be pushed several thousands of an inch further into the housing than it was designed to be. This would also have some degree of affect on the alignment of the axles relative to the differential (more side-loading of the axle and axle gear splines).

If it's your vehicle, then it's your choice as to what you do with it, but the gasket is cheap, and puts your vehicle's rear end setup back like it was engineered to be.

3rd member-to-housing gasket (for a 9-inch rear) is Fel-Pro p/n RDS 55074 (or, O'Reilly p/n for the same Fel-Pro gasket -- ROL DS14210).

 

[65ShelbyClone]

I used a gasket, no copper washers, and a thin layer of Fel Pro red RTV on both the housing and the center. I haven't noticed any new oil accumulation on the rear end since I fixed the transmission leak.