my dad has a '96 bronco and recently the rear diff cover got a rust hole in it, he's gotton a new cover for it and wants me to install it. he said that when he checked the oil leve when he realized he had a leak the oil looked red like A.T.F. so hes gotton a gallon of atf for it, im sure it aint atf in the differential, maybe a synthetic hypoid oil, but my ranger 8.8 takes gear oil and im certian the bronco/F150 8.8 would be the same, i just want to confirm with those who have been there and done that. its a 351/E4OD 3.55 open he got it new and it only has 55,000 miles on it, its mainly used to pull a 28' travel trailer, i cant imagine atf standing up to that sort of usage in a differential, but hey, ive been wrong before.

 

Factory fill was 80W90, but 75W140 is the one recommended now, unless you submerge the axle often enough to neccessitate frequent changes.

 

I changed mine last month. Used Valvoline 85w90 (I think that is the weight) from the zone. Since my 3.55 is Limited Slip I got a small bottle of friction modifier from the Ford dealer which is very important if yours is a LS. Look at the tag on one of the cover bolts. LS is 3L55 if memory is correct. However, if the cover has a rust hole the tag may also be gone. Again, if memory is correct, the door tag should have "H" in it. Haynes shows how to lay a bead of RTV gasket maker if there is no gasket. Clean mating surfaces well. Be sure to follow label on the tube. Mine said wait 15 minutes before reassembly for it to film over. Not very difficult if you take you time and clean cover mating surfaces well.

 

80W90. Don't forget the additive if you have limited slip!

 

Most manufactures now reccomend RTV for the cover instead of a gasket. I've always been told the gaskets tend to leak anyways so to seal them with RTV.

 

I would use ultra black, better than siicone.

 

used ultra black, no problems there, what i did have issue with was rusty brake lines, had one fron and rear rupture on me while i was moving it around. got it all fixed though.