Hello Greg,
The unit bearing could be the issue. Quick way to tell is to left the tire off the ground while it's still mounted to the vehicle. Grab the top and bottom of the wheel and see if it has any lateral play. If it does, you'll need to hub bearings. If not, you may have a bent axle housing. Id so check to make sure the wheels them self are not bent. Also check the tires for bubbles, out of round or out of balance. I hope that helps.