I have a 2002 Ram 1500 4x4 QC that I believe is vibrating in the rear (feel the vibrations in seat but not steering wheel). I had the tires balanced but it is still there. No wiggle in the drive shaft or missing weights on driveshaft. Is there something I'm missing?

It needs a new U-joint somewhere in there. It is a common problem and you won't find it by looking or wiggling the driveshaft. They sieze up and vibrate. Replace it with a greasable non-Mopar joint.