The dealer can install what's called anti-spin. The difference from what I understand is One is computer controlled, and the other is set up with clutches. Go out to the truck and on the passenger side of the 3rd member is a sticker. It will say 3.92 TRU-LOCK or 3.92 ANTI-SPIN. Not sure what tru-lock is, but my BEE has it and I leave 2 tire marks. From what I understand it's not a limited slip, but it's not a posi unit either. Long story short,,,, I sure hope you have better luck than I did getting info.