Every "limited slip" from the factory works slightly differently, but they all do the same same thing, which is provide traction by locking up the wheels when the base power wheel slips. No locker or limited slip locks up both wheels at all times, hence allowing differentiation of the axles. Spools or "Lincoln Specials" which are differentials home welded, often with a Lincoln welder, do NOT allow differentiation, and DO lock the axles together at all times. Aftermarket limited slip units like the Detroit Locker keep the axles in sync most of the time, which make for jerky street driving, especially when they're new. Factory units like the "Sure-Grip" allow more more slippage than their aftermarket components. The Ford units ( Trac-Loc ), also used in AMC rears, burn their clutches after 100,000 miles and have to be replaced. I've never owned a GM vehicle, but I know the Chrysler limited slip is known to last. And yes, if you turn the wheel one direction, the opposing wheel will rotate the opposite direction when the vehicle is up in the air. If you turn the wheel one direction, and the other turns the same direction, then you have an aftermarket unit like the Detroit, or a Spool/Lincoln.