Leaky Rear End won't seal

redsn95gt

Member
Aug 5, 2010
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Ever since I tore apart my rear end to do my gear swap, I've had a leak on it. So I waited til I ordered the Trick Flow aluminum cover so I could have that extra capacity and the heat fins etc, its a real nice piece. So I installed it and it was starting to rain so i just grabbed the paper gasket they supplied, left a little bit of fluid inside, torqued it and said ok i'll let it sit lets see if the paper works. Sure enough, it was leaking. I knew paper gaskets suck but I just wanted to test and now i can confirm.

So then I pulled the paper gasket. My mating surfaces were perfect, I gasket scraped all the old sealer off on my rear end housing so it was perfectly clean and wiped it with brake cleaner. I did a nice even bead of Permatex Black (the so called "ultra high oil resistance" type), installed that and then later filled my rear end with AmsOil gear oil and ford friction modifier. Double checked my torque settings, all good. For the first 48 hours, it was fine, next day i'm seeing my precious AmsOil starting to seep through!! This is not cool.

So whats the voodoo i need to do to make this thing not leak. I'm not understanding why it would be at this point. I mean the permatex stuff is really good normally.
 
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Can you use the paper gasket with the permatex? Or better yet, maybe use some type of foam or rubber or compressible style material that is sufficient for use on a differential along with the permatex. I wouldn't trust permatex alone with any type of fluid. I did once and had leaks.
 
You sure it's not a pinion seal. If the pinion seal leaks it leaves an almost invisible trail back down to the back cover.

Kurt

Yeah that is my thought too, I use Permatex Black or "The Right Stuff" all the time, let it site overnight when ever possible and then fill....no leaks. I do tend to put a little blue loctite on the fasteners, if you have porosity in the housing it could be leaking up through the bolt threads.
 
my rear end wouldnt seal with a brand new fel-pro gasket and ultra black. So i put the cover on and put a thick bead of ultra black across the bottom of the cover and it hasnt leaked since.