Recently my truck started doing something weird with the speedometer. When I come to a stop, it the speedometer needle sometimes moves around between 10 and 15 MPH. It doesn't do it all the time, only when at a complete stop with the engine running. There is no change in engine RPM, and the truck doesn't move at all, so it's something with the gauge, a ground, or speed sensor I'm guessing. When moving, the speedometer works fine. No ABS light or anything.

I know the rear speed senor is a common problem with these trucks. Could that be causing it? What else should I check?

 

That happens to me when i rev the engine. Its jumps to about 15-20mph. Vibrations maybe?

 

In my case it isn't the engine RPM. That stays constant...it idles normally and engine RPM doesn't seem to be affecting the gauge.

 

The contacts on the cluster can get corrosion and cause them to not make a connection anymore. I have cleaned mine up once but has come back.

My tach is currently opting to work when it wants or just read wrong.

 

mine did this it turns out it was a bad cab ground..check your ground cables ..also did it when my alternator was going out just last week

 

Well it looks like I will have plenty of things to check then. Corrosion and a loose ground are both very possible with this truck. I've gotten some water on the inside on many occasions and it's been down its fair share of rough roads and trails. It just seems very odd to me that it only happens when stopped at idle, and that the speedometer seems to function normally and accurately the rest of the time.