Speedometer moves around when stopped...
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?