I have a 1980 C6000 dump truck with 366 motor and automatic transmission that is not shifting. Drive, reverse and neutral work but I think in Drive it is stuck in second. When manually shifting thru 1st 2nd and 3rd there is no change. The oil level is correct and not burnt looking. When manually shifting an automatic this old are you physically moving the spool in the valve body or does it use solenoid valves to shift? Any help would be much appreciated.
Possibly the governor, depending on type of transmission, which would help.
Ya sorry I don’t know will try to find out. It just puzzles me why I can’t shift manually.