I'm at a loss for where to check next. Truck is a 2102 4X4 2500. The popping feel is subtle but noticeable. I've replaced the ball joints and track bar. During the ball joint replacement I scrutinized the wheel hubs and front u-joints and all seems smooth and tight. I'm wondering if problem is in the back. I rolled the windows down and it seems to be coming from the back but not sure.

 

A 2102??? Damn, that had to be expensive.

Are you using 4x4 on high traction surfaces? That'll make some interesting noises...