speeometer wires?

[pewster]

I have a question about a speedometer I got in a junkyard from a 90 suburban. It has a trip meter and has 3 wires that go to a little box that then goes to a plug that you can unplug from the truck harness. The speedo seems to work ok with these wires unplugged, just wondering if anyone knows what the heck they do. I haven't checked it out on the road yet, just spinning it by hand.

[zieg85]

Probably for the cruise control

[pewster]

Thanks. Didn't think about that. I'm putting the gauges in my 80 chev c-30 and it doesn't have cruise. Does anyone have the schematic for the cruise option?

[zieg85]

I don't but I am always looking for a parts truck with a complete "working" unit to put in my 85. 

[Captkaos]

Have you looked at the diagrams in the tech forum?  There should be one in the 81-87 that lists the speed sensor.

[Marc]

On an 87 that's a speed sensor.  Don't know when they went to the transmission mounted one.