I had a similar sound coming from the back end of my 2005. It bothered me for about a thousand miles. When I was putting a new rear tire on, I found one of the bearings rusty and shot. It had no wiggle and felt smooth turning the tire by hand. The bike only had about 7500 miles on it, I live in a desert and don't ride in the rain. I suspect the previous owner, who only put 2500 miles on it, went a little overboard with the power washer. There's 3 bearings in the rear wheel.