I've been trying to tune a problem out of my truck lately, but am now starting to wonder if it is a problem with my trans? Truck is an 02 7.3/4R100 with 37" tires and 3.73 gears. The trans was rebuilt to factory specs 10k ago with the only addition being a Factory Tech valve body. Only since my TDP chip has the problem arose. Even now in the stock tune and the daily/econo tune I do not have any problems. Problem is in my agressive street tune and extreme tune, the trans acts up in top gear under boost. It shifts fine-nice and firm, never slips, etc. In top gear accelerating, the truck used to make 25-28 PSI of boost locked up in top gear just by rolling into the throttle. Anymore it feels as if the converter unlocks under boost, around 20 PSI. There is a definite point where the RPMs rise around 300-400 RPM. It *feels* as if the converter is unlocking, but it shouldn't be. The truck still makes plenty of power in top gear. I notice it most when towing a trailer. 70 MPH, top gear, slight grade and the trans feels like the converter unlocks when it still has plenty of oomph left. My tuner (Tony Wildman) has been able to lessen the effect slightly by increasing line pressure, but he has already increased it to a point it shouldnot have to be at. He also tells me that he has put the same files in other trucks with no symptoms like mine. Is the converter slipping? I still have a warranty on the trans, but I'm sure they would say it was fine if I tried to get them to fix it, since it only happens in certain situations. Is a BTS my only option? What does it sound like is happening? Any help appreciated.