I'd make sure that you didn't install the clutch plate backwards. There is a flywheel side and a pressure plate side. The flat side goes toward the flywheel, and the side that sticks up faces the clutch diaphram. It can make a rattling sound and still work, although it doesn't have a lot of holding power. It will usually sound like springs being rubbed against metal (which is what is actually happening - the springs in the clutch plate are rubbing against the flywheel).