What is a good brand and weight for a 12 bolt posi ??
Thanks for your help........alan

I used G.M. axle lube its part #1052271 thats SAE 80W-90 with the posi additive,you can get this at any G.M. dealer...kind of simplifies the problem

Thanks alot .........alan

Once you choose your gear lube, for less than $5- go to your Ford dealership and get FORD additive I think it is 4 ounces. The stuff is magic!

Thanks....alan

I use Amsoil synthetic lube, it has the additive built into it for the posi. It works great in my new Eaton 3.08 posi. :D

Thanks......alan

Considering your location and temperate climate...

Schaffers #209 suspended moly, straight weight 140. With 4oz of the Ford friction modifier.

If you are using a later model fiber clutch EATON... I would sway from a full synthetic.

I run amsoil synthetic

I used to run the Royal Purple synthetic 75w-90 with the 4oz. bottle of GM limited slip additive. This time around I used Mobil 1 synthetic 75w-90 with the GM additive.

I don't want to start the whole synthetic "vs" dino debate, but I will tell you my experience. I ran Redline synthetic with my Eaton posi and it chattered like crazy. I tried adding the GM posi additive and it still chattered like crazy. I talked to Eaton and Redline and they both said not to use synthetic with a posi. I drained it out and put in Valvoline with the GM additive and it is now smooth as silk. I understand that several people here are having good luck with synthetic oil so let me say this. If you run synthetic and it chatters, drain it out and put in regular gear oil. I think as long as you are running a quality lubricant of any type the rear gear will outlast the rest of the drive train.