i am probably goin to change my diff fluid this weekend with Redline 80w140 fluid (it has the friction modifier already in it) and i am planning on replacing it by dropping the cover so that i can inspect the gears and all. I was talkin to the service manager at ford and he says there is no replacement gasket for the diff, they make their own silicone ones!!????

i know people on here have chnaged their diff fluids, so how is it done then?
and is this the best choice in lubricants?

 

They use a silicone sealant that vulcanizes at room temparature. You can buy some down at your local auto store. There was a thread on this not too long ago, just do a search if you want more info.