This is driving me nuts. At slow speed, like parking lot or driveway speed I get a rattle / knocking noise behind the driver. Never hear it even on bumps at highway speed. All it takes is small bumps and uneven surface to initiate it. From drivers seat it sounds like it comes from behind the rear set back area. Anybody else have this or had it and corrected it? Basically been doing it since new and noe has 9500 miles. Help a brother out.