Sounds like something is off balance

Having a stethoscope to listen to the axle housing could be a quick way to find the issue. Listen near the axle bearings, and the housing. Could be bad bearings in there. I know you said you replaced the axle bearings, but sometimes, new parts are ****. I had 2 new power valves fail on my car. you can also remove the rear wheels, and drums, and see how it sounds. Drums are balanced like every rotating part. Just don't step on the brakes, you'll blow out the wheel cylinders. Check for missing weights on the driveshaft.