Could be a broken wheel baring. Get the wheel that is making noise up off the ground and rock it towards the motor and back out toward the fender with your hands a 12 and 6. If it rocks back and forth, you need to replace the baring. Next try rocking with hands at 3 and 9. if you can move the tire without moving the steering rack, you have an outter tierod bad.
Hope this helps.
