Yes I know its been gone over many times, but I just cant seem to get a straight answer using search. And I dont want to go through millions of posts.

I have an 87 firebird with a stock 10 bolt with 3.23 open diff.

I need to know if I can just throw a series 2 or 3 posi in and bolt it up. First off, which one do I need, 2 or 3?

Second, Will I have to shim it, or mess with it in any other way, or is it pretty much a open carrier-to-posi carrier swap?

 

3 Its always best to re-verify patterns and so forth so Its a tossup if it needs anything or if its a perfect gear pattern and slides right in.

 

you need a 3 series carrier. measure your back lash before you take the original carrier out. install your ring gear on the new carrier and install. check/set the back lash to what you had with the original carrier. remember you can't change the total shim thickness on the carrier only the arrangement of the shims from side to side.

 

thanks guys. One more thing. I have the 7.5" rear or 7.625" rear?

 

Yes, if the cover has 10 bolts. Most likely it has 26 splines (early model, 89-back).