[Walt Fricke]

The speedo and the ODO get their initial signals from the same place: 8 magnets attached to the ring gear in the transmission. When the car moves, these magnets ground the odo signal circuit 8 times per right rear wheel revolution. There is no way that this can cause a sticky gauge.

For the odo, these pulses either turn a motor which turns the odo gear cluster (which is how the old cable odos did it - mechanical rotation of a counter system)or do something else like pulse a solenoid every so many pulses and cause a gear to move a tooth for every X rotations or fractions of a rotation. Again, things don't stick.

The speedometer needle is different - these pulses are translated in an electromagnetic force which causes the needle to move against the pressure of its spiral spring. Something in that system could get stuck. Send it to a speedometer shop - they can fix it.

Checking the odo is easy as pie, though - just use the mile markers on a highway.