I have an 88 silverado ext cab that the odometer will only register if you are at highway speeds. Speed registers normally on the speedo at all speeds. I repaired a cracked gear from the motor which drives the odometer after it stopped registering altogether last year. Don't know what to look for or how to test any further. Changed the speed sensor because trans fluid was leaking out of it but still no miles at lower speeds.
Thanks for any help.
Dan

 

Maybe the motor is bad.

 

Would you know what voltage to apply to motor to check it?
12volts? Or other and on which terminal?
I can't find a full schematic to trace it to see if it flows through some transducer or relay

 

I don't know the voltage. It may be easier to replace the motor or cluster with one from a junkyard.