Maybe I'm old school, but when I jacked this car up the other day and spun the wheel, the other wheel turned in the opposite direction. In the old days, that was a non-posi rear end. I know both wheels light up when launching, (believe me I know!), I was wondering what type of differential do these things have to allow it to hook up like a posi? Can somebody explain in detail how this rear end works? Thanks

 

I had a lego car once that had a posi differential... but it was open, so I learned how it all works. I can't really put it into words, mostly because I don't know what all the parts are called

but seriously that's how I figured it all out. With a lego car I owned when I was a kid.

It has something to do with the fact that if both wheels can't immediately spin their respective direction, another gear kicks in and hauls the whole thing in the forward direction instead.

 

Up until '98, GM used clutch style (Auburn) posi units. The clutch style posi works like you describe as "old school". Starting in '99. they switched to a Torsen style posi unit, which has no conventional clutch packs. They use a worm gear, and I would be making something up if I said anything other than they work like your 2000, but will spin both tires under power. Also there are no clutch packs to wear out, but that doesn't mean they last forever either.