I suggest you call Kirt Koeller.

First of all, your car cannot move without torque converter period. There is no 'extra' strain scenario. It is possible that the torque converter is not locking into overdrive.

Don't let thoise guy work on your tranny. They obviously don't know transmission. A compentent shop would have the scanner trigger functions in the transmission to find out which component is not working properly and then they fix just that part... alot of time is it just dropping the tranny pan and fix the component.