I know I am opening Pandora's Box, but how do I tell if I have POSI, LS or open. I jack the rear up - spin one wheel. Now, if its limited slip (aka POSI) the other wheel will spin in A: same direction, or B: Oppisite direction. If its open, which way will it spin? Or will it even spin at all? thanks in advanced!

 

Spin the driver's side. If the passenger side spins the opposite direction, it is an open rearend. If they spin the same direction, you have a limited slip, more often called a posi, although it's not a true posi.

 

alright. now - when you say limited slip, you are talking about a clutch type unit, and posi is mechanical (inertia???), right? Any explaination is more than welcome!
Also, is the only RPO code that denotes limited slip G92? Thanks!