Dan1969 - That noise is going to be ur brake pads shaking inside the calipers. I just bought an 02 a4 and had the same sound. Very load and sounds tinny(thin metal sound). I was told to take the pads out and coat the back with an anti-squeal brake backing spray (CNC brand was suggested), re-install and press the brakes so it sticks to the piston. Haven't done it yet. Maybe this week. U can test this theory by lifting the car and hit the tire from the bottom, hear it? Now take your finger and press on the pad from the back side of the caliper, hit it again, and no rattle.

Another rattle that I had was the rear bumper supports that attach to the bottom of the bumper were not connected. Therefor hanging loose ......

 

Thanks H1078, I was thinking it was the pad but didn't quite make sense to me how, so CNC anti-squeal spary, will look for it, the car is going to go into storage for deployment so I hope I get it done before I leave.

 

I have a 1997 V6 quattro I'm experiencing the same problem. It is the rear passenger spring broken. Since you will getting new springs get lower springs ;-).