check your axles out too while your back there. I just encountered this same issue on the right rear of my GXL... some vibration during driving/braking accompanied by a thrumming noise from the rear of the car. I inspected the rear and I noticed that the Right rear outer boot on my axle has aparently split open and is now splattering grease all over as I drive... this could be a result of some other issue but... I bought a used axle yesterday just in case. So DJ...you have a tool to pull that bearing do ya....
