My 400 coupe has/had the same problem. The neutral safety part still worked as it is a separate circuit as others have noted. I removed the switch assembly (console can stay just shifter plate to be removed) and disassembled the switch body (black plastic and metal). The metal part has tangs that secure the plastic body. Inside are sliding plastic pieces that engage metal contacts similar to your horn contacts. The plastic wears down. I was able to adjust the metal contacts some to allow for the worn slider. Worked for a year or so and now I have to do again. Going to see if I can melt a little filler on the piece that actuates the metal contact. Can you tell I'm on a strict budget? As others have said, I believe there is now a replacement available just in the last year or so. I have seen it listed in the Classic Industries reproduction catalog. Either way you go, enjoy . Hope you can see backing up again soon.