Hey all I've got a craigslist 80E that I put a Transgo HD2 into, also running a 258mm single disc Circle D stall. The truck drives and shifts totally normal. I've disabled torque management. But at, I would say, 50% throttle or above if I am accelerating, the 3rd to 4th shift feels fine, and then right before the converter locks the rpm's flare 2-300rpm. It's actually quite subtle and I didn't really notice it for months. I loaded a completely stock 80e segment and it still does it. I'm thinking it might be one of the solenoids, because I came across this thread:

4L80E shift to OD then engine RPM flare - Hot Rod Forum : Hotrodders Bulletin Board

Anyone experience this? I'm about to put the turbo on and any quirks or issues will become magnified!

 

Disabling PWM and making other adjustments to converter lockup seems to have fixed the problem. In case someone does a search in the future, I highly recommend using this guide to do a baseline trans tune:

How To: 4L60/65E trans tuning. Shifting/TCC/TM (w/ Pics))