diagnos a noise in running gear?
4x4 GMC 1500 has a "whooping" noise much like a tire loosing a belt might make. new tires, aligned, bearings and ball joints new in last few hundred miles. noise increases with speed and is more pronounced in reducing almost like a weight is shifting in running gear. U joints old but do not seem loose front or back. wonder if it could be a drive shaft or a bearing in the rearend or something in that direction. feels like in rear but not absolutely. vehicle does not vibrate at any speed. 350k miles. have changed drive shaft and u joints years ago. this came on gradually about 6 weeks ago and now quite clear but not loud.