I have a 1994 GMC Sierra, 4x2, Automatic. The problem I encountered was, while driving the transmission wouldn't shift automatically or manually. Had the transmission rebuilt and the problem still exists. Since this year they came out with the 4L60E transmission. My next step was to see if the computer is bad. Looking for computers is a little difficult because there's different part #'s. How would I determine if the one in the truck is correct, and if that is the problem? Like I said, I need help please. Thanks for the future assistance.