I will be swapping out my rear 3rd hopefully tomorrow and I was wondering if it's best to use a gasket or RTV on seal for it? I ordered a gasket from AutoZone but I also have red and gray RTV.

 

The gaskets are known to leak. Don't use it.
Spread a bead of grey RTV around the 3rd's mounting flange and call it good.

 

^ This. End thread.

 

Thanks for the replies.

 

It's RTV for me!

 

grey urtv. make sure you clean the third gasket surface and the housing surface with brake cleaner so there is no contaminance on there and you will have no leaks

 

Do you guys immediately tighten it down...

Let it harden, then fill with fluid?

 

I always hand tighten the nuts let it sit about fifteen mins then torque it down

 

Use the Ultra grey/red/black by Permatex. RTV isn't oil resistant, whereas the Ultras are. I have done countless thirds and oil pans and t-cases on Cruisers, always used Ultra Black, and never had a single leak. Now when I worked at the Dodge dealer, we were required to use RTV, and were constantly redoing leaking components. But Dodge would just pay us again, so it was ok...

 

"Ultra grey" is RTV.

 

yes it is. but permatex makes quite a few different types, read the labels and youll find one that is specificaly designed for use with oil. its one of the ultras.

 

I have gray RTV by permatex made for gear oil. I'm planning to use it.

 

I thought RTV was normal silicone gasket maker. The really potent, stinky stuff. My bad. I learn something new every year...

 

This is what I use my seals around gear oil:

http://www.permatex.com/products-2/p...t-maker-detail

Also here is some pictures

gasket scraped off:


rtv on:


and new (to me) 3rd member:



Now I have a curious question. If I spin either of the wheels the flange on the 3rd doesn't move. But If I spin the flange the wheel turn. A friend says it is a posi-lok 3rd. How does this thing operate??

 

Ok not a posi because that has to have a cable to engage it. When I spin the yoke both wheels spin forward. When I spin the left wheel forward the right wheel spins backwards. Yoke doesn't move.

 

Sounds normal to me,
As for gasket, ive never used one putting a diff center back in.
Just a nice smear of Threebond Grey (same as rtv maybe?) never leaked.

 

Perfectly normal for an Open/standard carrier differential. The wheels will turn opposite as long as one isn't held still. If you turn them both in the same direction at the same time then the pinion will turn accordingly.

 

FIPG ftw