we have a plane Jane 67, with a automatic. to our surprise when we went to move it wouldnt move, so we pushed it onto a tow dolly, put it in Neutral, and towed it at 25 MPH down a back road 4 miles to our new house. when we got there and unloaded it and we added ATF and it started moving, great! it was acting like a wheel was locking up feeling (weird) then pulled it up the driveway and tossed it into Park.
well, heres the oddity, it moves through the gears fine, but its in Drive. put it in reverse, its still in drive. what the heck would cause this i cannot check fluid because its trying to go in drive, wont engage park we checked all linkage etc all is fine.
I don’t know much of anything about transmissions but would seriously consider the vacuum modulator? See if when you pull the vacuum line off it if it is leaking fluid. Also do you have vacuum there? That along with fluid levels is about the extent of my knowledge so far.
I have heard similar things when people try to push start a car with an automatic or tow one in drive. Apparently the pump is not driven when the engine is not running and the over running clutch, a series of roller bearings and springs called sprags, welds itself together. I hope this is not your issue. A core C4 is pretty cheap and they really are not that hard to rebuild.
If someone has worked in the trans before and pulled the valve body, the shift lever in the case could have come out of the gear select valve and it is stuck in drive. I had that happen to mine, but it was always in reverse.
As for the order of operation, it goes like this:
1st gear: Forward clutch applied, one way clutch holding while accelerating, free wheeling while decelerating with car in “D”. When car is in “1”, low reverse band applied as well for engine braking when decelerating.
2nd gear: Forward clutch applied, intermediate band applied
3rd gear: Forward clutch applied, high/reverse/direct clutch applied (basically input and output shafts locked together for 1:1 ratio)
Reverse: High/reverse/direct clutch applied, low/reverse band applied
So, if your car has strong engine braking when in “D”, the clutch may be screwed up.
If it wants to go forward when in Neutral, a clutch is applied that shouldn’t be This can be a valve body, or internal linkage issue.
Also, if it still wants to go forward and can move under its own power, even when in park, the parking pawl is not engaging and it is most likely an internal linkage issue since that is mechanically driven directly by the gear selector shaft as it passes through the case.
Good luck, trans trouble shooting is a pain in the butt. I just finished doing battle with my C4 and finally got it sorted out.
i cannot check fluid because its trying to go in drive, wont engage park 
we checked all linkage etc all is fine.
