I have this friend. She has a cavalier(automatic) Im not exactly sure on the year but I think its a 99 or thereabout. Whenever you begin to accelerate it makes this sound, its not a constant sound.Its hard to describe but it sounds like a the noise your bike would make when you were a kid and would put a baseball card in the spokes, except metal on metal instead of baseball card on metal and a little slower. Once she gets up to around 50 it stops, but once she slows down it starts again. Any ideas?