i need to change the oil in my differential, the seal is leaking. Wondering if anyone could tell me how to add the oil and how much. thanks.

 

If you have the 5.4L, you will have the 9.75 rear end.
If you have the 4.6L or 4.2L, you will have the 8.8 rear end.

Unbolt the rear cover and drain the oil. Leave the top bolt loose and pry the bottom open to let it drain instead of dumping it all over the place.

Clean up the mating surfaces between the pan and the differential, and apply a thick coat of RTV to the cover or diff, and slap it back on and bolt it up.

There is a plug on the "front" of the diff near the pinion shaft. Open that up and pour in 4oz of friction modifier if you have a limited slip. If not, dont worry about it. Then, pour in the gear oil until it starts to run out. Should take almost 3 quarts.

 

use 75 w 140 full synthetic gear lube. you can get a generic brand at Wal Mart for about $10. quart. might be twice that at auto store... auto store has the addative in 7 oz. tubes.. i add the whole thing, it helps.

 

if your front seal is leaking, or any diff seals for that matter, you probably have bearings going out. check for metal flakes in the oil.

 

I have a rubbing noise in the rear somewhere on my 1997 f150 2wd 4.2 ltr. I took it to get state inspection done on it and they said it wouldn't pass because the rear U joint was shot. I new this already because I could here the clunk when getting on and off throttle. They replaced it and the clunk went away but the cyclic rubbing noise is still there. They checked the diff. oil and had to add a quart to top off. Rubbing noise is still there. My question is, there must be some kind of leak to lose a quart of oil isn't there ? I have never seen any oil any where. Is a quart low enough to ruin any bearings ( wheel bearings, pinion shaft bearings ) etc. ? Or could this be brakes making the noise, not sure at this point any ideas appreciated. Thanks Ps. Have not had a chance to run it on jack stands or anything yet. Everything happens in the dead of winter. lol.

 

johnnyboy i wouldn't recommend running anything on jack stands. Its an accident waiting to happen. Secondly, a quart low means at some junction your oil is leaking past a seal. A quart low would put your pinion bearing in jeopardy because the oil level that should be in it allows the bearing to always be running in oil. Yes, it does have a slinger on it, but at highway speeds that slinger won't trap enough oil to cool the bearing and subsequently that rubbing noise you hear may very well be bearing failure. Take your rear wheels off and remove the drums and look for any signs of oil seepage there, other than that im not sure what to tell you not being there to hear the noise myself. Good luck!