The issue you're describing sounds like your VSS (vehicle speed sensor) is going bad. This is normal for cars with high mileage. If you have low milage and the VSS is acting up, it means something else is wrong and in turn is affecting the VSS. Either way I'd get the transmission flushed.
If you get it checked and the code is P0500,
It might mean one or more of the following has happened:
* The Vehicle Speed Sensor (VSS) is not reading (functioning) properly
* There is a broken/frayed wire leading to the vehicle speed sensor
* The vehicle's PCM is not correctly configured for the actual tire size on the vehicle
First have them reset the code and see if it comes back.
Next, check all wiring and connectors that lead to the speed sensor. The location of the sensor depends on your vehicle. The sensor could be on the rear axle, transmission, or perhaps the wheel hub (brake) assembly.
If you get it checked and the code is P0500,
It might mean one or more of the following has happened:
* The Vehicle Speed Sensor (VSS) is not reading (functioning) properly
* There is a broken/frayed wire leading to the vehicle speed sensor
* The vehicle's PCM is not correctly configured for the actual tire size on the vehicle
First have them reset the code and see if it comes back.
Next, check all wiring and connectors that lead to the speed sensor. The location of the sensor depends on your vehicle. The sensor could be on the rear axle, transmission, or perhaps the wheel hub (brake) assembly.