maybe its the brakes, the pads chattering, the springs can get loose. maybe the dust shield is rattling. i know on some axles there is a pin that can rattle. did u check to see if it could be something like the sway bar bushings. not sure they would rattle but when one starts to break or a pc comes off it can be hard to dx. i had only 1 side break off several yrs ago and it had very odd symptoms. they r such a large bushing and if 1 side is still intact its hard to dx them.