I've only read the first page of replys. My appologies if this has already been addressed.
How can you tell what kind of diff you have without opening it up? The guy I bought my blazer from said it had a locker in the rear but when it is lifted up the tires still spin in opposite directions. Do posi's behave this way? I know opens behave this way and I thought that lockers do not. The limited slip in my Firebird will allow me to spin one wheel without the other moving when in the air. I heard from another person (who is usually just talking out of his ***) that a locker (maybe a posi) will behave like an open when in the air but if one tire is held, the other will be locked in with it. This is the scenerio with my Blazer. I no longer have a vehicle with a known open diff to test how it behaves in this situation.
Sorry if this has already been addressed. I'll find out when I have time to read this post tonight.