not a drive shaft problem, does in sitting in park. def. engine related. already tried a 400/440 ext. balancer. vibration was about the same.torque converter has no weights on it and I am assuming it is also wrong. am going to get a new one for 383 external to be sure and I want to replace it anyways.one torque converter fit's 383/400/440 ext. balance, so I would think the same would be true for a balancer, one ext. balancer would fit any ext. 383/400/440