This sounds like something I had 3 years ago. I had a bad PCM which MFG had to replace under the clean air act which has a year and mileage requirement. I also had a problem after the trans was modified which caused the truck to go into limp mode. My truck would lock and unlock at around 45 mph you would see the RMP's change each time it locked and unlocked. I did have a DTT trans back then because I though the trans was the problem and did the upgrades to fix the problem but it did not go away until I had the PCM replaced. I now have a different trans because personal :-{} choice and 2 broken output shafts when I was at the drag strip. I have a lockup controller on the trans which will cause the truck to buck at low speeds when engaged with normal driving its for the track only and needs to be turned off after the traps at the track or it will buck because of the tight converter and speeds under 35 MPH.
Attention: TDR Forum Junkies 
