Truck Repair: 1980 suburban transmission, manifold vacuum, vacuum hose

Question
The transmission will not go into reverse but into drive and park. there is a wire coming from a soleniod on the transmission that is hanging loose. any idea on what to check?

Answer
I would look for a place for that wire to connect first.
Sure that isn't a vacuum hose? I can't think of a solenoid, but if it is on the right hand side of the case, there could be a modulator valve, which I don't know if it will keep reverse from engaging, but worth a try. It would connect to engine manifold vacuum.
Good luck,
Van