Any suggestions on the type of oil I should put in my 69 12-bolt posi? I already bought a bottle of GM positrac additive to go with whatever oil I decide to use. Is it important to use GM brand oil or will any 90w oil be compatible with the additive?

Larry, i just changed the Ring and Pinion in my 69, i used all GM OIL AND ADDITIVE graemlins/beers.gif

Amsoil, LE Almasol, Schaffers........

A strait 90wt or a 90-140wt will be sufficient. The additive is parafin based and I have been using Schaffers and the others for many years as the schaffers is also parafin based and mixes very well.

I will add that the additive will mix with just about anything with no problems. If it were to seperate, it would be in a fully syntheic atmosphere. Sometimes parafin will not homoginize in a full synthetic..... sometimes.....

I use Amsoil gear oil in my new Eaton Posi 12bolt on my 69 camaro. It already has the posi additive built in from the factory. No need to add any other. If you use a pertoleum gear oil, then yes you need that additive.
good luck
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