The bed of my 2001 dodge dakota ext.cab. 4x2seems to bouce around and make loud noises even on very small bumps. I've hauled plenty of trips to the dump before. A couple loads weighed the rear down pretty good. The bed doesn't do this at all when weighed down. The bed was completed removed and bolted down extremely tight. The bed mounts right to the chassis. The rear shocks are new. I also completely removed the spare tire and fastening hardware.WhenI push up on the bed from underneath it makes noises and when I push down on the bumper it makes noises. However the bumper is also tight. Could it be the leaf springs? What can cause so much bedmovement?