speedometer not working

[jager420]

What's the most common issue with a speedomoter and odometer to only work once in a while, loose connection?

 

[Lost]

What year ? (2 newer could be plug on rear axle. Or the sensor is dirty or bad .

Posom (speedo Brain ) Also go bad but usually just quit .

If older cable may be bad .

 

[jager420]

89 f150 4.9 300

 

[Lost]

Cable or speedo head sounds like bad cable

 

[5Rangers]

To check the cable, raise the rear wheels off the pavement, be sure to block the front before so it doesn't roll. Pull out the speedo, disconnect the cable, start the truck, put it in gear and see if the cable turns. If it does the problem is in the speedo. If not, disconnect the cable at the tailshaft housing, turn it by hand while someone watches topside and see if it turns. If not, the cable is bad. If it does the problem is with the drive gear and the driven gear. Both are easy to change and cheap.

I just went through this process with my 88 and found both gears severely worn.