Dan, my challenger was doing the same thing. Had the shaft balanced and new u-joints, same prob. Changed the mount cause it was kinda sacked anyway, same prob. Then when my Dad had his new driveshaft made i thought I'd swap his old one in to see if it was any different. It was 5/8 of an inch longer than mine. Cured 80-90 percent of the problem. The resulting damaged tailhousing bushing could be the last little bit. I'm gonna change the bushing sometime this winter so I'll know in the spring if it helped. Hope you get yours figured out sooner than that!! Ha ha!!
