i blew the motor in my 2000 blazer, due to the rear main seal leaking. now i have a different motor in it and runs great BUT the the transmission won't shift out of 2nd gear, i am being told i need a new on board diagnostic computer, i have done some looking on internet, could also be a PCM or a couple of other things. i just don't want to be scammed. i would like some input on what else it culd be
THX