I searched on this, and the is wayyy too much varying information. Its like taking a shot in teh dark, and hoping you dont get chattering in the rear. I have a factory 2.73 10 bolt. I dont think the rear gera oil has ever been changed. Has about 140k miles on the rear. Its a posi (but right now it only spins one tire on a burnout). Im changing my ujoint tomorrow, and the gear oil while im at it.
Do I need 80w90 with the posi additive? And why does everybody says "GM" addidtive. Can I buy the addidtive from lets say Pep Boys? ....And someone told me that the rear end holds about 2 quarts. People on this site say they add 2quarts oil, and 1 quart addidtive. WHats the deal...and whats a good starting point?

 

Regardless of where you buy the additive, it's still made by GM.

It's probably more like putting in about 2 quarts of gear oil, and then 1 bottle of posi additive. The additive comes in a small 4 oz bottle.

 

Ill be changing this tomorrow. Ive heard of cases where changing the gear oil has brought the posi back. What if it doesnt?....Can just the posi of the rear end be changed without any precision gear work. In other words can I change the posi myself in my garage, and if so is there a place online or this site showing how to change it??