What is the speed sensor in a transmission?

Also known as the turbine shaft speed sensor, the speed sensor in a transmission is a magnetic coil that provides a vehicle's control unit with the rotational speed of the torque converter or the input shaft. This information is used to allow the vehicle to shift smoothly and run efficiently.

Although symptoms of a failing turbine shaft speed sensor vary depending on the model and year of the vehicle, common indications include a dead cruise control system, an unresponsive speedometer or odometer and an inability to shift correctly. A failing transmission speed sensor may also affect the vehicle's fuel consumption.