Thread: The Plymouth gets Cruise Control

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Cruise control for the 57 was a given for the upcoming trip to Tulsa.

Several years ago I used to use the universal aftermarket type that used the signal from the coil to sense vehicle speed. Unfortunatly I haven't been able to find those for a few years now. The only type I have been able to locate either use a signal from the computor or attach magnets to the drive shaft. As I don't do computors and have never had much luck with drive shaft magnets I decided to try something different.

I decided to go with a early-mid 70's GM cruise unit. I went with the simplest unit which is just basic cruise, a single button that sets speed, no tap up/down or resume, but for how I use it that's fine, and I like the fact that all that is mounted in the dash is a single momentary push button switch.

It's a little more complicated to hook up than the than the aftermarket system but most of the parts were installed as the car was going together so it wasn't that big of a deal.

What is required is a transducer, the vacume/electric switches that work off the brake and clutch peddles, speedo cables from the trans to the transducer and transducer to speedometer, the vacume pod and vacume lines and linkabe. I have about $110 tied up in the whole system that includes a rebuilt transducer, new cables, switches wiring etc.

The biggest problem was figuring out the wiring. The shop manuals and wiring diagrams I had access to were not real informative about how the whole thing worked, so a fair amount of time was spent figuring out what was supposed to happen.

Basically when you push the curise button it activates the engage and hold circuits of the cruise. When the button is released the hold circuit must remain hot to keep the cruise engaged. This involved getting a little creative with a solenoid and diode. The hold circuit additionally is supposed to run through a resistor wire, but fortunatly a ballast resistor drops the voltage the required amount.

I had already installed everything but the vacume pod and linkage when I built the car so yesterday I got around and finishing that up and trying it out. It works great, I still want to reroute the vacume lines and detail the linkage but that's minor.

In spite of the added work installing it, I suspect I may use the same set up on some other projects I have coming up.