Did the CSX's have any type of rear anti-rattle hardware for the brake pads? I have the most annoying rotational/bump dependant rattle coming from the rear brakes that goes away when the brakes are applied. I know the parking brake isn't the issue as I adjusted that sometime ago. I have not pulled the wheel yet but I'm sure this is the source. Any ideas about missing hardware maybe? It could be that the pads are just vibrating.
P.S. For those that don't already know this the CSX/CSX-T has a rear brake setup specific to just those cars.
Thanks!