So this is been going on since new or at least close to it. Bought new truck, tuned for a bit more power because it did not kick down well at 55mph and dealer said it worked normal. Use manual shift button and worked awesome. It seemed to work better and kickdown 2 gears after tune but slowly fade back to it's old habbits.
Fast forward 3 years later and fully tuned it will completely loose passing gear after 1 to 2 weeks of driving. Stab the throttle at 50mph and 6th is what it stays in. Download the same engine tune (not the trans tune) and it will downshift 2 gears at 70mph in standard mode or tow haul. 2 weeks later, no kickdown, re-download tune, trans will kick down. Turned off all adapts in trans tune, download and again works perfect for 2 weeks then no kickdown again.
Any Ideas are greatly appreciated !