What is the Transmission Speed Sensor all about?

Because both the engine and the transmission can rotate at different speeds, it’s vital that the vehicle’s computer is able to calculate the speed of the transmission’s torque converter or input shaft. The transmission speed sensor is a magnetic sensor that provides this information, allowing the transmission to shift smoothly. The sensor counts the internal number of revolutions of the transmission and transmits that information to the transmission control unit, where the data is used to determine the rotational speed. If the speed is too great, the gears need to be changed – it’s the same principle as watching the tachometer and shifting before the RPMs get too high while driving a vehicle with a manual transmission.

Keep in mind:

• On some makes, one of the engine mounts may need to be removed to access the failed part.
• Transmission speed sensors cannot be repaired, only replaced.
• While transmission speed sensor failure is not uncommon, many other problems can present similar systems such as ABS sensor failures. A full professional inspection will be needed to determine the actual cause of the problem.

How it's done:

• The transmission speed sensor is verified that it needs to be replaced. The vehicle is lifted and supported on jack stands as required.
• The transmission speed sensor is located in the transmission housing and removed.
• The new transmission speed sensor is installed into the transmission housing.
• The transmission speed sensor is connected. The vehicle is removed from the jack stands.
• The vehicle is road tested and scanned for proper operation of the transmission speed sensor.

Our recommendation:

The transmission speed sensor isn’t a part that can be inspected during normal maintenance, nor does it have a specific service interval for replacement. If you notice abnormal shifting or speedometer readings, have one of our expert mechanics diagnose the sensor.

What common symptoms indicate you may need to replace the Transmission Speed Sensor?

• Transmission shifts roughly
• Transmission doesn’t shift into higher gears
• Speedometer and/or odometer doesn’t work
• Cruise control is inoperative

How important is this service?

With a defective transmission speed sensor, the transmission control unit will be unable to determine the actual speed, which can make shifting gears difficult or even impossible. This will render the car unusable, so it is very important to have the sensor replaced as soon as it is determined to be faulty.