Hey guy's, new to forum I just purchased a 2004 FX4 screw w/79000 miles-the truck has a terrible shake in the bed at low speeds. It has new tires that have been balanced twice and a additive put in them the last time that is suppost to internally even them out has anyone had this type of problem? Oh, I went back with factory size tires

 

See any damage to the drive shaft or rear axle?