Ok, I am seeing something interesting that may apply. Many techs are getting a slight shudder @ 48-50mph, lock up, no lock up, no codes. Many have had success by cleaning the MAF sensor.
That would be nice to check as it is free and easy to do.
Give it a try.
Also, many others got this fixed with a reflash/upgrade of PCM software. I don't know if BP has the J2534 capability, but that also would be worth a try before tearing into it.
Test summary as follows.
Tests/Procedures: 1. Watch Torque Converter Clutch (TCC) slip RPM in scan data while the condition is present.
2. Disconnect the Mass Air Flow (MAF) sensor, road test, check for shudder.
3. Engage the tow/haul function, road test, check for shudder.
4. Watch a line pressure gauge, compare actual line pressure to desired line pressure based on Pressure Control Solenoid (PCS) command in scan data.
5. Determine if the shudder is at the point of TCC release, 4th gear release or if it occurs while the TCC and 4th gear is applied.
6. Watch short term fuel trim and long term fuel trim while the shudder is present.
7. If above checks are OK, reflash the PCM with the latest software, road test.