That doesn't sound good. I think you need to pull it apart and make sure it's all there and in accordance with the manual. The spring needs to be there to put the main plates under presure so you have a solid diff (i.e. so it doesn't slip). When you turn one rear wheel, the other should turn in the opposite direction - if it doesn't you have a problem. It should also be smooth with noticeable resistance, but not too much.

A high pitch noise indicates a slipper problem - the manual should tell you how to adjust it. Basically with the diff at the right tension, it should slip for a couple of feet under full power take off on a high grip surface. You will then need to adjust it to the racing surface when you get to the track.