I have a small diff leak after changing the fluid a couple of weeks ago. Ford Parts stated to use Black Silicone which I did. Has anyone had this happen and if so, did a gasket solve the leak for the diff cover?

 

If you don't follow the instructions on the tube, you may have a leak. I don't know if you can buy a ready made gasket.

 

Is it definitely the cover leaking? Silicone RTV is the recommended sealer. I use the grey "gasket maker" version. Here are a few typical reasons the sealing fails: mechanic gouges one or both sealing surfaces prying the cover off, cover sealing surface not flat from prying on it, one or both sealing surfaces not cleaned thoroughly, interior housing not fully cleaned causing lube to drip down contaminating sealing surface, incorrect application of sealant, not applying sealant fully around each bolt, improper cover bolt torque, and adding lube before sealant thoroughly dries (very popular).

 

Yes, I added lube before sealant dried. Live and learn.

 

Final something I can give advice on

Rear Diff Fluid Replace
9.75" Ford rear- has no available gasket.

Use the Black Silicon,

-Remove cover, drain old fluid, make sure to get the fluid from the bottom of diff as well.
-Clean cover and diff seal really good, use brake cleaner and a razor blade.
- Apply black silicon to both sides, level flat about 1/8" thick, dont get any to close to the inside. Let sit apart for 15 minutes.
- Put back together, insert bolts, tighten in a ring pattern then go around again, and again and snugg them all up, not to tight to push out all of the silicon.
- Do not add fluid, let sit for 24 hours
- Add fluid, if the tag says synethetic, get it, $15 bucks a bottle sucks but is worth it.
- Clean off the fill screw real good, the magnet traps the loose metal.
- Fill her up, top her off about 2.5 bottles.

Good Luck

It took me two times to get it right.

 

I appreciate all the advice on this one. Now I need to capture the new fluid I placed in it recently to install the silicone properly. I used the Valvoline 75W 140 Full Synthetic (like the tag).

 

Your suppose to wait 15 to 20 minutes for the silicone to tack up a bit then add the goods.

 

If you had used a gasket it would have only took you one time!
9.75 differential-FelPro part # RDS-55394
8.8 differential-FelPro part # RDS-55431
Any parts store that sells FelPro gaskets have these.Live and learn!

 

I got the picture loud and clear. Gasket.

Thanks

 

BlueOvalFitter,

Felpro# RDS55394 does not fit the 9.75 differential. How do I know? I bought one and it did not fit. I then called Felpro and they confirmed that it was not for the 9.75 differential.

JMC

 

JMC,i'm sorry about your misfortune there,but I was passing on info I got from a Advance auto parts counter guy.But,I do know for sure the 8.8 gasket is correct,because I have used them! :o

 

Now worries man. I just wanted to post so nobody else would get the wrong gasket. I ended up using silicone.

JMC

 

I've never had any luck using gaskets. RTV blue or black have both been 100% reliable. I tried to use RTV on an 8.8 three times in my Ranger.... finally gave in and went with silicone.

-Joe