Sounds to me the trans is not centering into the bell housing/pilot bearing. 3 transmissions???????? Same clutch???? Same bell housing????? Most trans are in the .002 to .008 run out spec, anymore than that and the throw out bearing hangs up, the clutch disc's don't/won't disengage causing just about everything discussed here. I doubt seriously any tech is going to get the dial indicator out and check to see if the bell housing is centered on the pilot bearing. I've done two bell housings where you have to get offset dowel pins to make everything line up, a time consuming job. My 2 cents.