housing seal is bad so i'll be replacing that soon.. what oil do i use? 80-90?

 

changed it today and it isn't leaking from the seal, it's leaking where the drive shaft enters the rear end. what is the problem and how hard is it to fix?

 

Its easy to fix. You will need a new seal, and new crush sleeve. set pinion pre-load and your done.

Also I would use the thicker 140 oil if you have a stock rearend.

 

If the rear is posi you will need a friction modifier added to that oil. If you are going to change the seal it is not hard like 440ram said but the pre-load must be set correctly by the book within 5 ft-lbs or you can destroy the rear.

 

do you know where i can read about it more in depth?