I replaced my 94 speed sensor with a 92 since my speedometer stopped working and i have a 92 parts truck. The cable driven sensor has 2 wires on it. What are they for and do i need them? The 94 had 3 wires so i just left it unplugged for now. Only noticable problem is the truck doesnt shift to 4th gear, but i doubt the wiring has anything to do with that.

 

You will need a sensor from a '94. That '92 sensor is useless to you. The third wire on the '94 will be for your speedo/odometer

The problems you will have without the speed sensor plugged in will be:
- No overdrive
- no daytime running lights (if you have them)
- truck will stall if you stop too fast
- speedo won't work
- odometer won't keep track

 

+1 to that.

First indication that it wouldn't work should of been that the sensors were different and with different wiring.