[rotorwrench]

The relay points can stick if they've gone bad and hold it in overdrive. If you try to push the car backwards it won't go. The troubleshooting instructions in that link will answer most questions. I'm not sure what happens if the wires are crossed on the solenoid but it's doubtful it will work that way. A couple of wires cross shorting could have some funky surprises but it depends on what wires might short together.