I have a clunking sound that I cannot figure out. It only occurs while driving, load or no load. From the drivers seat it sounds like its coming from the rear of the car. The thunk is consistent with the wheel rpm's. Its been going on for about 2 weeks now of daily driviing and only until I reach ~20mph. Begining this morning it became more consistent and lasting beyond 20 mph. Ive had the car up on jack stands looking for something loose in the wheel wells but found nothing. I spun the wheels by hand and all seemed to be fine. The sound I usually associate with a bad wheel bearing is a roaring sound (plus the reas are relatively new, fronts Ive never changed) so I dont think its them. Anyone with a similar experience that can shed some light here?