04 CC 2500HD with a thumping noise.
 

Has anyone here heard about a thumping that you can feel in the floorboards? I can feel it at 45+ while cruising. It feels like a balance problem, but I just had my tires rotated & balanced and the same thing. It does not effect the steering wheel, so not sure where it's coming from. I have about
28k miles on it.

Thanks for any help.

RE: 04 CC 2500HD with a thumping noise.
 

do you have steps on your truck. my dad had the same problem. his step was loose and when you hit any size of a bump it makes a thump in the floorboard. just a thought.