John Searcy

Under the shift selector inside the cab, disconnect the harness going to the shifter for 5 min. This will reset the TECU, but prior to that disconnect the positive and negative battery cables ((completely from the unit)) for 30 min, as this will reset/reboot the VECU and then do the shifter harness for 5 min. If there is a communication issue through the canbus line with these ECUs this processes should clear up the issues, if not head in to dealer for repair.

... I know who can get you exactly what you need. Call Mack One Call @ 800-866-1177 and ask for the phone number to the Mack Museum. They will be able to assist with locating any old parts.