I've noticed lately the RR wheel spinning on slippery corners, it used to not spin untill they both lost traction.What can I remedy this with?

 

I would think your posi trac is not doing its job anymore and that could mean some diff work coming up.

 

The factory "limited slip" does allow some slippage. It uses a set of clutch plates (7 -10 i think) with a tension plate. The clutches wear and the tension plate loses some of its spring over time resulting in more slippage/spinning than when new.