1984 speed sensor?

[Dvldog8793]

Howdy
Working on my sons truck. We found a small yellow box with wires coming out of both ends in the guts of the dash. Low and behold it has a AC Delco part number. We looked it up and it is a SPEED Sensor!

Can anyone tell me what type of signal it uses and where it gets it from?

....And Why does a truck with no abs, no computer, no auto trans....no NOTHING that could possibly need a speed sensor, have one?

Cant seem to locate it in a shop schematic.
I am thinking we will not be reinstalling but I am just wondering what it was/is used for.

Thanks!

[AKMark]

Did that go to the cruise control?

I seem to remember that in the past.

[Dvldog8793]

With more examination...we found that one end of the box is hooked up to a light that would normally go in the dash someplace. The wires from the box then go into the harness and out the fire wall. So far no luck locating what they hook up to.

This truck does have cruise control, not sure why the diesel system would need a speed sensor? I have a 1984 g20 van with cruise and I don't believe it has a sensor.

Still wondering what the speed sensor would get it's signal from?

Would this be a "55 alive" light? I know some vehicles of the time had little lights that came on when you exceeded 55mph.