Originally posted by rjl
When new the diff may feel a bit notchy but shouldn't lock up ever. Use the fluid that came with the diff and fill as per the instructions none of mine ever "locked".
My understanding of limited slip differential is that it is suppose to provides a certain amount of slip before it locks up. It works much like a normal diff but will lock up when one wheel spins much faster than the other or under full power. When it "locks up," the rear is essentially working like a spool, thus the understeer.