I had a rattle in the tailgate and found a loose locking motor. As the others say, it could be any or all of the hardware in there. If the rattle is the tailgate moving around in the frame, there is another fix. Loosen the two rubber "pads" on each lower side of the edge of the door. Pull back and drop the headliner so you can get at the hinge bolts. Loosen these a little and move the door so that it is centered in its opening. Tighten the hinge bolts. Now you need to adjust those rubber pads in and out until they each contact the frame equally when the door closes. I 've found that leaving the pad screws a little loose, moving the pads toward the inside of the door, and then gently closing the tailgate pushes these pads into nearly the correct position. I then open the tailgate and move each pad equally in a little bit and tighten the screws. This makes the tailgate fit snugly when closed instead of shaking with the bumps. My tailgate is much quiter now. Hope I was clear on this.

Hi Phil - had the same problem with my old brick. Found that EVERY bolt was loose attaching all the latches and other hardware. Also removed the interior trim panel on the hatch and found all that hardware loose also (ie - wiper mounting hardware, electric lock mounts, etc). Get your wrenches and spend about half and hour tightening everything up and you should be "good to go". RP