I recently had the same problem. I have normally just replaced the small gear that had a broken tooth and everything was fine. The last time I had a difficult time restoring function to the odometer. I had it back out of the car three times! I can remove the instrument cluster in total darkness at this point....

The last time I had it out I assembled the gears in the correct position and then positioned the armature of the motor. Finally I brought the circuit board into position and added the screws.

When installing the speedometer into the cluster be sure the connection pins are in the correct position. The teeth on the big gear are all in place aren't they?

For whatever reason the third time was a charm and the odometer is rolling again.

Randy