I spent all weekend swapping out my old 10 bolt open rear for a 9 bolt 3.27 posi. It was a HUGE pain in the *** but I got it done. Before, from a dead stop, I could fry the passenger tire at will and had NO traction, now I can hardly break them free and it seems like I have excellent traction. My problem is that when I power brake and do a burnout it only leaves one tire mark, the passenger side. I tried to do a donut but couldnt get it to do it. The rear was bought used and it seemed nice and tight, everything looked good and checked out fine. I opened my door and watched during a burnout and it looks like the driver side tire is trying to turn, but just isnt. But like I said, when I do take off hard, my traction is much better than before. Is the posi unit just worn out and working, but not at full strength?

 

Sounds like a worn out posi.

 

sounds like you should swap the gear lube first and see if that helps or not. otherwise you'll need the posi cones shimmed to get the posi to work again. what was your old gear ratio? 3.42/3.73? ??

 

I just got a nine bolt 3.27 rearend but need to know for sure if a posi.
could you look at by post label "please please look at my pig " and tell if this is a posi. there picture of it thanks

 

Old ratio was 3.42. I did NOT add posi additive as everyone says not to with the cone type posi. Gear lube was replaced and new gasket was installed (still available at GM contrary to what some people say). I definately have better traction, just seems weird that it is only leaving one strip of rubber.

 

you'd need the posi re-shimmed. and your lack of launching is due to the drop in gear ratio from 3.42 to 3.27 gears. There are articles you can search for to learn how to shim the posi or have some shop do it for you.

 

ALL friction based posi's, including the cone type, should have posi additive in them.