The vehicle is a 2006 F150 SuperCrew FX4 5.4L
I bought it on Monday, and have been noticing a small shifting issue.
Under light-moderate acceleration, the transmission will run through first, shift to second, then to third, and about when it feels like it should go to fourth, it sort of jolts or hiccups (very little RPM change), but it is fairly harsh (like someone tapped your bumper), then it feels like it locks the torque converter, THEN shifts up to forth gear.
It was hardly noticeable at first, but when I installed a program from my x calibrator 2 with firmer shifts it was VERY harsh. I returned the computer to stock and had my tuner try to smooth the shifts a bit. It was a bit better, but still there.
Now, if I lockout O/D, and accelerate all the way up to fourth gear it is perfectly smooth. I can then let it go into overdrive from fourth gear, and it is smooth.
Same story if I accelerate hard all the way through, 1st, 2nd, 3rd, 4th, then it locks the torque converter.
The problem is only under light-moderate acceleration, like normal starting from a traffic light. I don't believe it is an actual tranny problem since locking out overdrive fixes it, I think it is something with the programming. Again, it does this with stock software.
My tuner guy has no idea why it is doing this. I tried to datalog with the xcal tuner but I was unsuccessful.

What do you guys think? Could it be trying to shift and lock the T/C at the same time? The truck is not under warranty so I really don't feel like having to pay the dealer to plug their computer in to see what it's doing. I'm going to keep working on data-logging but any advice would be a huge help!
Thanks
Brian