I noticed mine leaking. Tighten up the bolts some one was real loose. Hope that was the problem. Noticed that there was black silicon under the plate and around the bolts. Is that how its sealed or is there a gasket?

 

Yeah its RVT silcone gasket. its easy to repair. why dont you use brake cleaner and spray it and clean it up then see where did leak coming from.

If you find its leaking thur the gasket then you ll need to remove the cover and drain the gear oil, clean up the "old gasket" (use razor blade) , clean really well, use brake cleaner to spray inside the diff. and outside where rvt silcone is then let it dry for few min, apply new black rvt silcone and wait few min then put cover on , torque to 30lbs i think, and wait for few hours then fill up new gear oil.

YOMAN!

 

If its the 8.8 differential you can go to any local auto parts store and buy a Fel Pro gasket for it.
part number; RDS-55341

 

Thanks for the replys.
Sould I go with OEM gear oil or is there an aftermarket brand? Going to go and see if its an 8.8

 

Well, if your user name is indicative of your current truck...a Black FX4 Screw will NOT have th 8.8" rear, as you have the 5.4L V8...which will have a 9.75" rear....

 

You're correct about his screen name! I have yet to see a gasket made for the 9.75 rear end! If it were me,ide go to Pep Boys and buy Royal Purple full synthetic gear lube;its about $11-$12 a quart.Also,Wal-Mart has Super Tech 75W140 full synthetic for $10 a quart!
One more thing,if you have a posi unit and the fluid says it has the friction modifier in it already,still go buy some from Ford and add it too! Go find an empty parking lot and do about 8-10 figure 8s to mix everything up in the differential!