Ford Repair Questions? Ask a Mechanic for Answers ASAP
Why does the torque converter appear to be locking up? What does it feel like? Could it instead be HARSH/ERRATIC/SLOW DOWNSHIFTS? If so, there is a tsb out on that saying to reprogram the powertrain control module (PCM) and the transmission control module (TCM) to the latest calibration.
If you want a copy of that tsb, here it is.