Bad tranny mounts are usually noticed by the tranny shifting when under a load.
The check is to jack up the tranny from below and looking to see if it disengages from the crossmember..
The dudes that installed BOTH of the trannys should be aware of a bad mount as it had to be transerred to the new trannys..
As much work as you have had done to that part of the Jeep I doubt anything that simple would be the cause..
Big JIm <img src="/forums/images/graemlins/pfft.gif" alt="" />

professional bovine relocation specialist