Me too. The instructions that came with my Eaton said 80-90 mineral oil with 7oz of GM addative. My local store dosnt carry a good full mineral gear lube so I put the Valvoline Durablend 80W-90 with one bottle of GM addative and havent had any problems with it.

 

I was thinking....maybe before I even noticed the leak the gear oil was really low and perhaps overheated or damaged the clutches.?

 

as i read through this post i see something that bothers me my tires chirp at low speed sharp turns and i did not think anything of this until i read this and it makes me if this is a problem i am definately pissed off because i just let my truck roll out of warranty can someone help or PM me or something

 

my truck does that too but i think it is from raised line pressure and a vett servo. i don't think i have a problem with my rear end! i don't know if you have any tuning that raised the pressure or any tranny shift kits in or not

 

Use non synthetic lubricant and 2 bottles of additive. For clutch style posis I use the ford stuff m19546a. The gm stuff is real good for Auburns, which were stock in many of their cars for a while. Ford has always used Clutch style units, and I have always had good success with their additive. You can try one, but some additives say 1 bottle per quart of gear lube. After you lube it up, get it to operating temperature then drive in figure 8's, that allows both sides of the diff to work evenly and saturate the clutches in oil.

 

Well, if it was under warranty, they wouldn't cover the differential anyway... (unless you meant that your stock unit is doing this?)

 

For the eaton use the durablend 80/90wt. And a bottle of ford limited slip additive,it's better and cheaper.