I have a 4l80e in a supercharged silverado 6.0 previously equipped with a 4l60e. I drove it with the scanner on it and it does certainly act funny especially when you move the gear indicator and look at the commanded gear. It goes from P R N D 3 2 1 obviously but the commanded gear doesn't follow that pattern at all. Its all over the place.
It also in low gear will kill the truck if you take your foot off the brake. (converter engaged) it drives "OK-sh" in D and 3 but the Converter locks way early and it shifts mega HARD as one would expect.
I looked at the tune and it appears to look ok to me but Im very poor at looking at these things but Im learning...slowly. I'm going to attach the tune file and a log.
The last time I had something stupid like this happen on another truck it was a botched segment swap.
truck tune.hpt21-05-08 12-28-50.hpltruck tune.hpt21-05-08 12-28-50.hpl