I just got back from a 2000 mile trip. I noticed excessive tire wear on the drivers side rear tire on the inside. The truck first started to wobble at the end of the trip at about 60 miles per hour. I rotated the tires and replaced the worn tire with a matching spare. The truck now shakes excessively at 35 miles per hour and up. It does reduce shaking at speeds above 65. I suspect a bad rear axle bearing on this side. There is no noise upon turning axle by hand though and there is no noticeable play when pushed on by hand. This is a single rear wheel drive vehicle.