Quote Originally Posted by 56pan View Post
My '93 C2500 6.5 diesel did the exact same thing. Only has a TCM and stored no codes. It was a bad ignition switch. Badly worn and with green corrosion. The clue is shutting it off, restarting, and the trans works right again. Hope this helps.
I appreciate everyone's input and the winner goes to 56pan and all others who suggested the ignition switch!! I finally had time to work on it today and changed out the ignition switch with a genuine ACDelco NOS part, just test drove it tonight, works like a champ!! I'm glad I asked y'all because I never would have thought that!!