*Overdrive is a device which is used to step up the gear ratio in the car. It is mounted in between transmission and propeller shaft.

*Overdrive is generally fixed on top gear only. Overdrives are fixed on gears other than the top gear for increasing the torque ratios available in some sport cars.

*Overdrive is a term used to describe the operation of an automobile cruising at sustained speed with reduced engine revolutions per minute (RPM), leading to better fuel consumption, lower noise, and lower wear.