We are getting a low hum and grinding that seems to get worse with more speed. We took it to a shop and they said it was the right wheel bearing. They replaced it and it helped slightly but got worse quickly. We took it to another shop and they said it was the bearing that had just been replaced! So it was replaced again...the sound is still there! Is this possibly a differential problem? If not..what else could it be. Noone has been able to get into the differential to check the fluid. We have not taken it to a Suzuki dealer yet, do we need to?