Have a buddys LMM that he just bought. Had all kinds of codes being thrown and truck wouldn't move, replaced the TCM and had a it programmed and truck runs and drives now but every few times you put it into reverse it throws a P0878 code and says "range shit inhibited shift to neutral to reset" then it works fine after going to neutral. I was thinking NSBU but wanted a few other peoples opinions since a local shop has already given him the run around. Truck has 225k miles on it and shifts great in the forward gears except this one code and not wanting to go into reverse sometimes. I have used the search feature for this code on this forum but none of the threads had any suggestions or answers really. I don't mess with the internals on these transmissions to much but would like to help him before I haul it 2 1/2 hours to Josh H. since he is the only Allison guy I trust that is even remotely near me! Any help is greatly appreciated.