Most of the time, my speedometer needle is steady and in the right spot. But once in a while, it will indicate several mph too high, along with some slight fluctuation. The tach and the GPS speed remain steady. What would cause this? I would think that a worn component would cause it to indicate low or bounce around all the time.

Also, where would I get a speedo drive gear with a different number of teeth, since I have 31-in. tires? I look on parts store websites and don't see any drive gears.

 

What year is your Explorer? Does the cruise control fluctuate with the speedo, or does it seem to behave independent of the speedo displayed speed? Depending on the model year, the calibration for the speedo may need to be performed through the PCM using a tuner or professional scan tool. Does your truck have ABS, and if so, does it work properly even when the speedo is acting up?

-Rod

 

It's a 1994. It has a cable running from the transfer case to the speedometer; has a plastic drive gear on the t-case end of the cable; has an electronic speed sensor next to the cable, which if I understand correctly, the speed sensor is just for the computer and has nothing to do with the gauge.<br />
<br />The cruise control occasionally surges a bit, but it doesn't seem to happen at the same time that the speedo is acting up. ABS works correctly; the light comes on when I start the engine, and then stays off.