Differential leaking

[ttraut@unlockit]

I think I know the answer and figured I'd check it with the experts.

My 69 Roadrunner leaks fluid from the differential. It appears to be coming from the top of the differential.

I believe I need a gasket. Am I correct or should I consider other things?

If it's a gasket I need, can I pick one up at my local Pep Boys?

Thanks,

Terry

[1972roadrunner]

i'm not sure if pep boys would carry it in stock or not...another thing to consider: is the fluid coming out of the pinion shaft? if it is you might wanna check that seal in there....other than that i think you have found it, hard to tell w/out a pic though... you might need to find a mopar place to order the gasket, unless pep boys can order one. thats not a very popular part so it might be a longshot... good luck!

also, a no-brainer: don't forget to pickup fluid because it will all be lost when you take the cover of...i find that 90wt works great in mine... have fun!

[71383bee]

If it's just a pumkin gasket NAPA or Bumper to Bumper or any other of the decent parts shops should have it or be able to get it quickly. I think I got mine from NAPA.

[1972roadrunner]

i live in a small town so everything needs to be ordered here and it always takes forever!! if ya live in a place like milwakee....things will be there, or ordered very quickly...

[dave571]

Which diff do you have?

If it has a cover(8 1/4 or dana 60) then you take the cover off and use silicone when you put it back together.

It probably has an 8 3/4 which doesn't have a cover. The whole gear set comes out the front. A gasket should be used on assembly.

Either way, if the leak is comming from the top of the diff, it's probably coming out the vent cap. It's a tin cap, on the hollow bolt that holds down the brake line/hose union. Some diffs like to throw a bit of oil out of there.

The easy fix is to put a piece of rubber hose on it(3/8"??) and run the hose up into the frame. Commonly done by 4x4 guys to keep mud and crap out of the diff. DO NOT block off the vent, or replace the bolt with a solid one! You will push the oil past the axle seals instead.

[pishta]

NAPA in stock for around 8 bucks for the paper one or a little more for the metal core one. I just swapped my 741 for a 489 and I used RTV since my paper one still leaked. Anyway, the top of the pumpkin doesnt get alot of soak, it does get some "sling" though. Just how much fluid do you have in their anyway?

[dave571]

Good point on the oil level pishta.

Check the level. If its over full, that may be the cause of the problems. Over full differentials are a very common cause of seal failure. If you correct the level now, you may avoid other problems.

How to check??

Pull out the fill plug using a 3/8 extension and ratchet. If stuff comes out, let it run out. When done, put the plug back in. If nothing comes out, put your pinky in the hole, and see how low it is.

[rumblefish360]

No gasket is needed for the 8 3/4 at all. Period!
The other rears have and use gaskets from the factory. But there not needed.
Spread a thick bead of silicone and let cure. (Not fully) On both sides to be mated. Sandwitch together and tighten up.
Good night Irene !!!!

[ttraut@unlockit]

Wow, go to bed for just a couple hours......

Thanks for the insights. I have a non-Dana differential. (Would that make it a 8 3/4?) I've put 90 wt fluid in a couple times now using the "pinky in the hole" method (maybe I should go back to bed 'cause that's sounding like fun right now....) and have never filled it more than I can feel with my pinky bent.

It ISN'T coming out of the vent cap but for the life of me, I can't figure out WHERE it's coming from! And it's flowing enough where I get a couple of drops on the ground if the car sits for 5 minutes.

I'm going to do the silicon treatment and see if that takes care of it.

Thanks,

Terry

[71383bee]

Just for reference the 8 3/4" rear does not have a bolt on cover in the rear. That is a dead give a way that it's an 8 3/4". All of the other kinds have a bolt on rear cover. The dana is kind of squarish looking almost oval and it is guite large compared to the other rear ends.

[dirty dan]

The gasket is replaceable with silicon ,no problem. If you have a sure grip rear be certain to use the right gear oil . And fill it until it starts comeing back out of the hole.That is the corect leavle. Hope it helps.

[Big Ray]

Check the pinion seal . I just had to replace mine. It was dripping a little. Mancini has them for less than 20 bucks.