3rd member gasket leak

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DentalDart

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It's me again! Woohoo!

So yesterday I put some oil in the 3red member thinking I'd be able to drive the beast today... came out a little bit later to find that it was leaking. **** me. Leaking at the gasket seal between the 3rd and the housing, so here I am draining it today. The picture of clear oil draining out is so sad... I checked and it wasnt running out of the drain plug not was it running out from the pinion seal (where the yoke it to the drive shaft)

When I assembled the 3rd member I did it while the 3rd and housing was out of the car so it was easy and there was no previous oil in it.

So I'm doing s new gasket on it today. I've read threads where people say rtv only, where they say gaskets, some say rtv and gasket, some said **** it and run it dry (this was a joke). RTV (grey/black/red/untra blue) Should I try and get another paper gasket? Paper gasket with rtv (this is what I used last time, I usually smooth the rtv out instead of leaving it as a bead, which was probably how it failed?) I also have gasket shellac (it doesn't seem like it would be as thick as the rtv though?)

Thoughts for sealing it back up? Put rtv on housing or on the 3rd member?

Also oil for it. I bought Castrol Axle 80w-90 API-GL5 limited slip (put in valvoline with limited slip additive yesterday) will this stuff be enough? Or should I add in some lubes guard limited slip supplement additive as well?

Thanks!

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Go to a motorcycle shop and get some sealant they use to seal engine cases with. Like Hondabond 4 or Yamabond. Use it with your gaskets, torque it down and don't worry about it.

I've split a few old Honda cases and resealed them with Hondabond and never had a leak. Crap, the stuff could probably stop a leak on a Harley.

Permatex Aviation Form-A-Gasket works pretty good to. It's fuel/oil resistant and doesn't harden. Just make sure you wear some rubber gloves and have some mineral spirits on hand when working with it because the crap has a way to get all over things if you're not careful and is messy.

I'd go with what they use on motorcycle cases for best results.
 
Mine has a 50 year old gasket that has become one with the housing. I just left it there and put some black rtv over the top of it. Hasn’t leaked yet
 
You had a gasket and RTV and it leaked? I'd check both surfaces for nicks, flaws or distortions.
 
Use a gasket dry, Never RTV. The gasket is also a slight shim . While its out dry it good pour thinner in the housing. I have found many housings leak at the center lower weld not welded properly. Check it while its apart with a thin liquid such as thinner.
 
Found the culprit! Gasket tore at the bottom at some point.

Well I would use a gasket but I doubt anyone has one in stock, I'm going to look right now.

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Surprised you don't use the Pink Reusable gasket from Dr. DIFF . . .

I actually already had two gaskets, the only thing new I got for the rear end were the axle shafts.

I am picking up a new felpro gasket right now and I will try the gasket technique again. I needed a brake line adapter and another bottle or 2 of gear oil anyways.
 
Found the culprit! Gasket tore at the bottom at some point.

Well I would use a gasket but I doubt anyone has one in stock, I'm going to look right now.

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That is a common place for it to tear, as the housing does not support it very well there. If you fumble at the install, it likes to tear there. If you back it up or remove it, it still likes to snag and tear there.
I have never used any sealants or glues, just the dry gasket.

I agree with Oldmanmopar that the weld is somewhat prone to leaking.
 
That is a common place for it to tear, as the housing does not support it very well there. If you fumble at the install, it likes to tear there. If you back it up or remove it, it still likes to snag and tear there.
I have never used any sealants or glues, just the dry gasket.

I agree with Oldmanmopar that the weld is somewhat prone to leaking.
The last time I had the center section out of the 8.75 I reinstalled it with just a gasket, and it leaked, not much, a drip would form in an hour or so. Took it out, put a thin film of black rtv on both sides of the gasket and the leak was resolved.
Personally, I think that the cast iron, fully machined differential side is probably pretty good for flatness and sealing. It is the fabricated, welded together housing side that would be likely to have flatness and sealing issues.
 
Cleaned both the housing face and the 3rd member mounting surface with a dry cloth then a microfiber with brake fluid on it. There were some little pieces of gasket in the housing so I fished that out.

The housing mounting face has some little inverted dimples on it and it looks like there is a little crease on the inside where 2 pieces of metal were welded together. I'm for sure going to use rtv on both sides of the gasket and pray that I dont leak again.

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RTV is not for using with a gasket. It is called "gasket maker" because it is used in the place of a gasket. Using RTV on a gasket can cause it to squirm out of shape and slide out from under whatever it is you're trying to seal. Either use the gasket dry, or RTV by itself. I've had the best luck using the high temp red RTV. Those housings get pretty warm. I've never once had RTV leak when I got done.

Also, as @Oldmanmopar said, double check the weld in the bottom center of the housing. They were often pretty crappy.
 
3rd member on.

used rtv rear axle gasket maker on the gasket, put it on the housing, then a little on the 3rd member. It seeped through the faces which is what it did on the rtv instructions video and another video I watched on youtube, even though I used less rtv that either of the people from those videos.

If this ****** leaks I'm royally going to be killed by the wife haha. I figured this rear end would have been better than a ford but.... just kidding it's still better than a ford rear end

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Neither here nor there, this is my take on sealing just about anything. If the seal is breached before the fastener, its going to leak.
 
ATF will leak out the smallest pinholes in the bottom weld, fill the bottom with it and watch for a leak. I had 1 that did and took me for a ride when I started swapping out gaskets. That 60 lb pig is no fun to juggle down there on your back. I ended up bolting the pig back in, grinding off the weld bead and re-welding the bottom seam. Finally fixed the leak.
 
ATF will leak out the smallest pinholes in the bottom weld, fill the bottom with it and watch for a leak. I had 1 that did and took me for a ride when I started swapping out gaskets. That 60 lb pig is no fun to juggle down there on your back. I ended up bolting the pig back in, grinding off the weld bead and re-welding the bottom seam. Finally fixed the leak.
The weld on his housing sure is ugly. That was the first thing I thought when reading this thread. Great advice with the transmission fluid. I'd use something with more of a solvent base.
 
ATF will leak out the smallest pinholes in the bottom weld, fill the bottom with it and watch for a leak. I had 1 that did and took me for a ride when I started swapping out gaskets. That 60 lb pig is no fun to juggle down there on your back. I ended up bolting the pig back in, grinding off the weld bead and re-welding the bottom seam. Finally fixed the leak.

Yea it is big time no fun lifting that thing on your back under the car. I smashed the **** out of my finger.

The housing bottom still had fluid in it and wasnt leaking at all.
 
Yea it is big time no fun lifting that thing on your back under the car. I smashed the **** out of my finger.

The housing bottom still had fluid in it and wasnt leaking at all.

Damn ya He Man,
Using the floor jack cradle makes Pumpkin R & R easier but i guess that's why they give ya Ten Fingers so you can smash the **** outta one and still have Nine left..Lol
 
Damn ya He Man,
Using the floor jack cradle makes Pumpkin R & R easier but i guess that's why they give ya Ten Fingers so you can smash the **** outta one and still have Nine left..Lol

I used a floor jack and the third member tipped over a bit and just enough to crunch my finger haha
 
I shouldn't say **** yet, gonna R & R mine next wknd and yer probably half my age.

I'm old too! Have rheumatoid arthritis and had heart surgery at 21. :poke:

I just filled the diff up with fluid let's see if I come out to any leaks in the morning! :popcorn:
 
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