Hi islandnick, Welcome to 2carpros and TY for the donation
Could be a problem with the parking pawl linkage-investigate from the gear shift to the tranny for any worned out components
CAUTION: All parts must be handled carefully to avoid nicking or burring the bearing or mating surfaces. Lubricate all internal parts with clean automatic transmission fluid before assembling them. Do not use any other lubricants except on gaskets and thrust washers. These may be coated with petroleum jelly to facilitate assembly. Always use new gaskets and seals when assembling transmission.
Parking Pawl Mechanism
Unfasten and remove parking pawl guide plate from case.
Remove spring, parking pawl, and shaft from case.
Working from the pan mounting surface, drill a 1/8 inch hole through center of cupped plug. Pull plug from case with a wire hook.
Lift end of spring off park plate pin to relieve tension.
Parking Plate Shaft Replacement
Thread a 1/4-20 X 1-1/4 inch bolt into park plate shaft. Pull shaft from case with screw.
Reverse procedure to install.
NOTE: When installing guide plate on case, make sure that actuating rod is seated in slot of plate.
Wednesday, March 24th, 2021 AT 1:53 PM