I'm swapping out a worn out 6L90 transmission that has over 220k on it in a 2011 GMC 2500 HD with one that has 89k on it from an identical truck. Will it have to be reflashed or reprogrammed to work?
As long as it came out of another like vehicle, the Transmission Control Unit (TCU) should not need reflashed. What I mean by like is, another GMC or Chevrolet 2500 HD truck of the same year. As long as we are on par there, there shouldn't be any issues with the swap.