Overdrive, in the context of vehicle transmissions, represents the highest gear ratio. Its primary function is to reduce engine speed at a given vehicle velocity. An illustration of its effect is observed when, at a consistent speed, engaging this feature results in a decrease in the revolutions per minute (RPM) displayed on the tachometer.
The implementation of this higher gear yields several advantages. Most significantly, it contributes to enhanced fuel efficiency, particularly during sustained highway driving. Reduced engine RPM translates directly to lower fuel consumption. Historically, overdrive mechanisms were often separate units added to transmissions, but modern vehicles typically integrate them within the transmission design. This integration provides smoother operation and improved control.
