I have had this persistent issue with my transmission that has been driving me crazy and I finally pinned down the symptoms...
My transmission is newly built, but I have had an issue with it overheating on long trips. I have an issue with the trans will shudder sometimes. I scanned the car today with HPT and noticed a few things. During lockup the TC slip rpm will fluxuate from 70rpm to 0 and back. I also noticed that on the highway during acceleration with lockup, the car will shudder as the TC slip RPM climbs up towards 700RPM.
I tried adjusting the duty cycle and I had no change. I suspect that my TC is fried and I need someone elses opinion before I put the cash forth to swap it out.