Friend of mine trailered his Challenger into town for a show....Newly rebuilt 340 and 727 ( 2500 miles total on each ). After driving back from a cruise-in, it wouldn't shift out of 1st. We checked the fluid level, and the kickdown linkage, both OK. Took it out for a short drive, it shifted into 2nd at a much higher rpm than normal, then eventualy into 3rd. Noticed a lot of vibration coming from the driveshaft area towards the front as speed increased in 3rd gear. Trans was making some wierd noises in anything except park and nuetral while checking the fluid ,After coming to a stop, it starting slipping in 1st and refused to shift again. We put in back on the trailer, and he headed home. He had a real hard time getting it off the trailer, as it was vibrating and slipping real bad trying to back up. Everything was replaced during the rebuild including the torque converter. Any ideas??

Might be the governor in the trans. My 72 started doing that. Had to wind it up a little tighter and let off the throttle and it'd shift. If not it would never change. I also noticed a loud click from under the car when it shifted or I decelled and it shifted down.