I just bought a 1998 Z-3 2.8 fully loaded, or I thought so. After many hours of detailing I had the back of the car on jack stands and found that it had a open differential and not a limited slip?. Before my purchace I looked up all the standard equipment and opptions. The limited slip differential was listed under standard equipment. The car has traction control and I don't no if BMW is calling this there posi rear end. If you no whats standard issue please write back.