90 Buick Century custom. Odometer started acting up, not recording actual miles driven. Then it was OK for the next 1300 miles . Now its not moving at all and speedometer stopped working. Both are analog type. Do not have cruise control, trip odometer or ABS. Transmission is shifting fine. No service engine light has come on. Instrument cluster basic. Bad planetary gear or faulty speed sensor?
It sounds like the vehicle speed sensor may be faulty. Sometimes the speed sensor nylon gear wears and strips causing the sensor not to turn.
If it were the planetary gears then the transmission probably won't move.
It is a fairly simple repair; you will need to know how many teeth the gear has to keep the proper ratio for the correct speedometer speed.
If you can get someone to scan the computer they can check to see if there is a speed signal being sent from the sensor. If you don't have a signal then it will most likely be the speed sensor. If you have a signal then it could possible be a speedometer issue.