2014 Silverado Shift Flare

Michael0connor · July 20

Bit of a long post coming up but any info appreciated!
2014 L83 Stage 3 BTR Cam, supporting head work, kooks headers and circle d 3200 stall. 6L80

Had a harness in my rear passenger door break, 4 broken wires, obviously happened over time however i only noticed when the interior lights stayed on, cluster said the door was open and the window wouldn’t work. Along with that the airbag light would come on, the truck start acting funny, and the most noticeable thing of it all was the transmission start to slip/flare from 2nd to 3rd gear while about 25% throttle, WOT never gave an issue both D and Manual. Went to GM and got the harness i needed and replaced it. The flaring stopped from 2nd to 3rd instantly however developed a terrible flare from 3rd to 4th gear under any throttle both D and Manual. The only way to shift it is to select manual mode, back off throttle, select 4th gear and come back on throttle. The tune that had been written for the truck always flared 3-4 under WOT but never gave issues at 70% and below, i had been waiting on a retune to rectify this. I tried reinstalling the tune to see if maybe when the harness broke wires got crossed and somehow confused the TCM, but no luck, instantly kept flaring 3-4th. Trans is running normal temps, fluid is at correct level and has no particles in it and doesn’t smell burnt.

i replaced the transmission 2 and a half years ago with a brand new one and had all modifications done on the truck and 20k miles ago by a reputable shop.

Has anybody got some tips for me, or have had similar issues, i run HP Tuners and can send a data log to anyone who can look for bad things.
would it be possible the crossed wires could have fried something and is causing this or does it sound more like an internal problem? I’ve read forums of similar problems ending with all different results such as complete transmission failure to a fault MAF sensor. Any help and advice is much appreciated