odometer

my odometer(mileage marker) on my 88 c/k1500 GMC 1/2 ton pickup V8 5.0L stopped working correctly, it records the milage then stops then continues. It goes back and forth, how can I fix this problem?

most likely the speedo drive gear. it's a cheap piece of plastis that looses teeth sometimes. it goes in the extension housing on the transmission.