What is on the front for driven equipment? I'd be curious if they are all in alignment? If they are pulling the crankshaft forward it could be an issue. Do you know how much fore and aft movement of the crank you started with? The only other thought I would have is the "stack"of clearances in the transmission is allowing to much forward movement. It's possible that the bearings in the trans have to much play and when the clutch packs are pressurized it's pushing the Convertor forward. The crank being pulled forward I have actually seen. The transmission pushing the TC forward is plausible.. I haven't witnessed it. It may be possible to test the theory though.