O3GMC

I had an Eaton posi installed a few thousand miles ago, and just realised that I might have needed to change the fluid after 500 miles or so.....or is this only neccessary when changing gears as well? I re-used the factory 3.73's and conventional 10w-30 (I think) and a bottle of friction modifier.

12sec.5.3

iTrader: (1)

I don't think you'd have to change it, but it shure wouldn't hurt. I thought you were supposed to use gear oil like ''80w-90''??????

12sec.5.3

iTrader: (1)

Have you ever experienced it leaking. I've tried factory gasket, gasket material, and permatex and it still leaks. Maybe mine is bent. Probably gonna get a new cover.

LS1csherm

I dont think 10w30 is correct. - might check that one.....

Mn Avalanche

the gear oil for factory g80 units are 75-90 full synthetic.with the eaton its 80-90gl5 with limited slip additive.10W30?thats scary

O3GMC

sorry for the confusion, I was kinda heading out the door when I was posting......I meant 80w-90

James B.

iTrader: (1)

Yes, 80/90 Mineral-Based gear oil is correct. 4oz. Limited-Slip additive (friction modifier) is required for the 8.5/8.6 10-bolt.

Absolutely never use synthetic with an Eaton Posi. You have it right.

I changed my fluid after the first 500 miles. It was clean. I also followed the break-in procedure like it meant life or death. The best arguement for opening it after the first 500 is to check contact and look for signs of trouble, before they become expensive.

O3GMC

Thanks for the info James, I wasn't sure if there was any specific break in for just the posi, but I was easy on it for at least 500 miles.

I used the gasket that came with the install kit from Randy's Ring and Pinion...and no leaking as far as I can tell, although I haven't been under there in quite a while.