Recently completed a swap in the white truck. I'll give you the complete history of Trans to my knowledge to perhaps help ideas.
The 80e is a 06 model. 70k miles. Pulled from a truck that got clipped on the side. Friends and I installed a transgo hd-2 shift kit. ( I throw that in to make clear if you think this could be part of the problem by all means say so you won't hurt my feelings. ) install went easy. Using stock converter. I've double checked the wiring to the PCM. I have not yet doubled checked my work on the sensor that plugs into valve body.
I've tried two tunes from different years so far. The segment swap isn't as easy as it should be. Some dildo through the trucks history loaded a custom VCM OS ID. I don't know if this was done by the first tuner TR or perhaps from gm. Word is the first owner was a paralyzed individual and it had everything a up for him to control it through the steering wheel. That was all removed when he sold it.
NOW what it's doing is. The gears are shifting as soon as the truck starts moving. I put it in drive it will jump to 2nd by 10 mph. 3 right after and be in high before I get to 15 mph. Also doesn't want to down shift until at a complete stop. Strangely and by complete accident to keep it from going dead I found it would shift into reverse while moving ( I had hell getting the park-neutral safety switch off the 60e and installed on here so that's a possibility ) it is throwing me two Trans codes.
P0740
P0785
Both coming back to solenoids. Any help greatly appreciated. I do currently have hptuners a copy of tune to see if the segment swap is working correctly. Current segment swap is from exact year model as mine.