My 64 Valiant 273 has a vibration that comes and goes in about 2 sec cycles from about 40 to 65 mph. I thought it might be the ball and trunnion at the front of the driveshaft, so pulled the driveshaft to check it out. As the transmission has a flange at the back, the car can be run without a driveshaft so I thought I would run it up in gear assuming it would be smooth. I started it, hit the pushbutton for drive and ran it up to speed and the vibration was there and the same. I tried it again in neutral and there was no vibration. It can't be anything behind the transmission and with it smooth in neutral, I would think the torque converter must be ok. Any ideas on what would cause this in the transmission. It was rebuilt about 2000 miles ago.
