I posted a while back about my leaking rear differential.. well, it's leaking again..

After reading and researching, i've decided to go with the Fel-Pro gasket with RTV on either side. If this doesnt work, I'm welding it shut.

Now, the general consensus (from searching..) is that Fel-Pro P/N# RDS-55394 will work.. except one individual who i dont remember saying it did not fit.. I have a 9.75" rear end... I dont want to hear "Oh just use RTV.." because it didnt work the past 3 times, so now I'm buttoning down and using a gasket..

Just want to make sure I have the right one. Thanks in advance!!

 

RTV should work, you 100% positive its leaking from the cover? no gouges in the mating surfaces and they are clean? no dribble of oil?

reason im asking is because we use silicone to seal everything where i work. sure it leaks, a few years down the road after running 24/7

 

I can't even count how many diffs I have taken apart. i used RTV on every single one. If its leaking, you are doing something wrong, or something else is going on. Make sure both surfaces are smooth. CLEAN em up good. Bring it to a machine shop to have em surfaced if need be. When going around the bolts, lay a thick layer on either side of the hole, so it wraps around each bolt. Put LOTS on. You can take a razor to the extra that comes out.

Welding it shut would be one heck of a mistake IMO.

 

Use the gasket! I always use them on 8.8 differentials,with no problems or leaks!

 

better yet, get a mag hytech dif cover ! Added cooling, more fluid, drain hole, even a dang dipstick for your diff ! Plus, they have built in O-ring seals, works great everytime. Just another option.

 

I've been inside my truck's rear axle at least twice, and I've had no problems using blue permatex to seal things up. are you cleaning the hell off the cover and mating surface before closing the axle up? use lacquer thinner or something along those lines to clean the gunk off. are you sure there isn't a gouge in the cover or axle mating surface?

 

Are you letting the RTV dry up a bit before filling it with fluid and driving off? Also supposedly if you tighten it down too much the sealant basically oozes out and there is not enough to make an effective gasket.

 

Use a gasket and your RTV nightmares are over!

 

i think i've been in the rear axle 4 times in 6 years? all my RTV holds up, really got mad at it once when i used the "right stuff", SOB wouldnt come off!

 

....so, it's the right gasket?

 

something is wrong beyond RTV...I have never had one leak on me...you are either not putting enough on or something...I usually put way too much on and let it sit for at least 4 or 5 hours to let it set up before putting oil in it

 

They do not make one for the 9.75 differential.

I crossed your application with the part number and it only is used for the
250's and the excursions.

Like stated before, either use the BLACK RTV sealant, carefully making sure matting surface is clean and knick free. After reassembly, let stand for at least an hour before adding fluids. It would not be a bad idea if you would let it sit for 24 hours before adding ANY fluids to the differential.

I myself have done this several times, always with a positive outcome.

I have since bought the mag-hytech cover and couldn't be happier with it.Here Is the link to the covers. May be costly, but, it is far better in the long run, IMHO.

 

Hmmmmmm,then how do you explain this?

http://www.jegs.com/i/Trans+Dapt/969/9049/10002/-1

 

steve, "The Right Stuff" example.

 

A Few notes for people who might run into this..

1.) The RDS-55394 gasket is not made for the 9.75" rear end, it is for the 10.??" rear end, found on some F250s and F350s with the heavy duty payload package. It is significanly larger.
2.) A new cover from a Ford dealer is $48 (in CT..)
3.) I ordered a gasket from the above. Im using it with a small bead of RTV on either side of it.