Reverse Lights Not Working

Randy, still having problems, huh?
Your '74 Dart's neutral safety switch has three "prongs". A prong is the short metal male terminal sticking out of the switch that makes contact with the female terminal on the end of a wire, completing the electrical circuit. What I call the "connector" is the round plastic fitting that is molded around the three female terminals, and it plugs "onto" (rather than "into") the three exposed male terminals ("prongs") on the switch - it basically is held in place by the action of the female terminals gripping the male terminals. I'm not certain if the plastic connector is designed to have a lip molded around its inner circumference that "snaps" into a groove around the switch's outer circumference, holding them together (or vice versa) - I haven't inspected both of them closely.

Since I never replaced one, I can't say for certain, but I believe the neutral safety switch is "threaded", rather than "plugged", into the transmission housing. It really does nothing more than act as a ground for the switch. With the gear selector in "Park" or "Neutral" the switch circuit is closed and allows the engine to start. If the gear selector is in any other position other than "P" or "N", the circuit is open and the engine can't start.

Obviously, this only pertains to the "start" circuit. Once the engine is running, you can change to any gear position you choose and the switch has no effect. It's called a "safety" switch for the obvious reason - the car won't start while in gear to prevent it from causing damage or injury.

The other two outer terminals of the switch are where the circuit is closed when the gear selector is in the "Reverse" position. In any other position, the circuit is open and... no backup lights. Again, the ground is made to the transmission housing.

Theoretically, if all of the wires are solid with no breaks and have no bare spots rubbing to cause a short, all of the wire and connector terminals are clean and make good, tight connections, all of the bulbs are confirmed to be good with tight sockets and clean terminals, then I can't see how the neutral safety switch or its associated "connector" can be your problem.

Since I haven't seen what goes on inside the transmission to make all of this magic happen, I can't say what might be a possible issue in there. If a lever, pawl, tang, tab, prong, tine, or whatever you might call it is malfunctioning in there, sorry, I can't help.

Keep us posted,
Jerry