2011 6l90e issues helppppp GM A6

[Turbolq9]

Hey all, helped a buddy swap the trans in his 2011 silverado 2500 6.0. When you drive down the road it stays in 1st gear and will not shift. Goes into PNRD fine no issues. i read a lot of stuff saying the TCM needed to be reflashed by GM etc. Was just wondering what actually needs to be done and if its just an OS issue or what. os:24270599 trans id:24274145 CVN: D67A

[verlon]

24270599 is a 2015+ OS
You need to find some 2011 calibration with 24256125 OS for your 6l90.
Be careful not to mix 6l90 and 6l90lcc transmission and calibration.

[Turbolq9]

Thank you much. Will see what i can find!

[Turbolq9]

i greatly appreciate your help