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Rear diff cover seal issues- Help

Incredible Hulk

NAXJA Forum User
I am at my wits end.....
I have resealed the rear end of my truck twice now. The first time it leaked right off the bat. Probably because I put in fluid 5 mn after I put on the gasket maker. However, last time I let it harden for over an hour. Now it has started leaking again. This was warped pretty badly, to the point you could lift one edge off the floor about a 1/4" by pushing on the other side. However, I ground it down with an angle grinder to flatten it out, and it was pretty dang good. So, I assumed it would work since gasket maker is flexible and fills in where needed etc. However, here I am again- starting at a leaking rear end. It left a 4 in. puddle (Yes, a puddle, not just a spread) between 10pm and 9am this morning. So, it is a pretty good leak. What the heck? SHould I really just send it to someone and have them machine it down to perfectly flat? WIll that solve it? What else should I be trying? It is driving me crazy. Help.
I'm not a fan of that gasket stuff in a tube, probably because I have NEVER gotten a good seal long term with the stuff. I use gaskets, I also don't like allen, hex or torx heads. When I reinstall a diff cover I also treat it like a head, snug everything down then start tightening down from opposite sides.
I keep a roll of gasket material, the grey and brown/tan cardboard looking stuff, around for when I need it now and nobody has one, the cover, xacto knife, some indian head gasket sealer, cutting board and I'm happy. Just my .02.
OH, to check the cover for flat, find a table saw with a steel deck, lay cover on and run a feeler gauge around it. Thats how I do valve covers that required prying off only I have a jointer for doing that.
The covers probably not square but you might want to try "Lubelockers"
I've been real happy with my Lubelockers for about a year now. Whose cover is that? Although it's probably too late now that you've ground on it, I'd still try contacting the maker to see what he will do for you given that it was so unsquare.
I made that diff cover, that is why it is warped. Where can I get a lubelocker? That looks like a good idea....
Incredible Hulk said:
Hmmmmm, I dont know about that. If my diff aint square, its gonna be tough to get that to seal....

Repeat, gasket sheet, xacto, cutting board...indianhead gasket cement, bolts with bigger heads...
when i use the rtv / gasket maker i will set it up on the cover, let that set for 15 or 20 ,inutes then instal the cover tightening like RichP said getting it snug then tightening it down from opposite ends.

works pretty well for me.
I am using the lube locker gasket front and rear and my diffs don't leak at all.

Although it is hard to tell in the photo but the orange traces are raised on the gasket, so it isn't flat like a piece of paper. I can't imagine a gasket sheet working better than this.
Incredible Hulk said:
So where do I get indianhead gasket cement and gasket sheet? Napa?

A good napa might carry it but since most shops don't/won't cut their own gaskets you might have to hunt around for one that does. I have a parts store that is also a machine shop. It is normally carried in a roll form, 24" x 2 or 3 feet long. You can even get the cork type that is much thicker and might be better for your purposes.
Take the cover to an auto machine shop. or any machine shop and have them cut the surface true. some machine shops have big belt sanders for surfacing heads and manifolds. have it done that way. then all you need is a small bead of RTV.
Don't just patch it up. fix it right.
I have had excellent experiences permatex rtv stuff, and in my familys vehicles, hundreds of thousands of cumulative miles (of course the covers were pulled & fluid changed in much shorter intervals). Good for diff covers and other things like dressing certain gaskets. Used to use orange but now grey. I was not satisfied with the black, its crumbly. Do it right though, make sure scrape and clean both surfaces with solvent REALLY WELL and don't expect it to set up right away. Squirt some onto trash and watch how long it takes to cure. I'd put the diff covers on in the evening and the next morning add the fluid. My invention helps, a really big funnel w/ long tube connected and a metal hook attached (hang the funnel to side of vehicle) Dump in the right amount of fluid and walk away while it fills up. And yeah don't torque the bolts in a circle, go across the cover like a wheel. I mark w/ chalk on the bolts already torqued or b/c I forget things. I like the looks of that lubelocker thing... I would also worry about the allen bolts holes loosing their shape if I lived in the salt belt.
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I do rear diffs all the time. After I clean and dry the cover, the Mopar diff sillicone goes on instantly and with out waiting. I install the cover imediatly and torque the bolts. I have never had a leak. I think there is something up with your cover. I have lots of mopar sillicone you can have for free if you want.
have it machined flat, then just use good old rtv black. use plenty of it and dont worry again. i have my first leak now since using it and that is only because i peeled the cover back on a trail and beat it back without resealing.
Having a shop true up the mounting surface is the best idea. From the pic you posted, it looks like the rim is thick enough that this shouldn't pose a problem at all.
One other option that may or may not work would be to try to straighten it out yourself with some heat. Bolt it onto the diff with no sealant at all and tourque it down. Then use a torch to apply some heat to the cover then let it cool completely. By doing so it might then take the flat shape of the diff mounting surface. That's just an idea - haven't tried it myself.
buy a ford 9"
then there is no diff cover...

If it's aluminum, the torque and heat trick will not work. do like Ryan sez...get it surfaced. As mentioned above....the surfaces must be cleaned with solvent for silicone to stick...I use Brake Cleaner. If you use silicone, put the cover on as soon as you apply the bead and let it set before filling.

The best "silicone" on the planet is Toyota cam plug sealant...16 bux a tube but worth it. If you put it on clean and wet, nothing will leak past it.