Newbie here, not sure if this is the right place to post so looking for feedback.

04 Yukon Denali
6.0 4WD
Swapped NP241 Transfer Case from a Tahoe
Using for sand drags
I pinned the PCM for the low lock signal
When in high range with the low range signal in the off position the truck shifts through the gears fine at WOT. When I put the t case in low range and switch the signal to on, the trans only sifts through the gears at part throttle. At WOT in low range it will not upshift. I've tried manually selecting the gears and it still does not shift under WOT.

Any help with advice or how to post in the proper forum would be awesome. I do not have HP Tuners program now but will purchase if my problem can be solved with programming.

Thanks!