What is Overdrive?

Many cars of the past decades have enjoyed the addition of the overdrive mechanism. Cars like the Triumph 2500, the Toyota Cressida, and the Honda Accord have at times made use of the excellent overdrive gearbox.

Overdrive is an arrangement of gearing which produces more revolutions of the driven shaft than the driving shaft. An overdrive unit raises the drive shaft’s speed of rotation relative to the gearbox output shaft, changing the final drive ratio. What the driver will notice is that when the over drive kicks in under normal driving conditions, the engine rpm will be reduced about 30 percent while the vehicle maintains the same road speed. As a result, the fuel consumption of the motor vehicle improves markedly. Leisurely and fuel efficient touring can be enjoyed by all occupants with the addition of an over-drive unit in a motor vehicle. What many people sometimes overlook is that overdrive units help to prolong the engine’s life because the motor does not work as hard at lower engine revs. For quick acceleration, the automatic gearboxes are still able to dive down to a lower gear to gain better torque and engine power, but when steady progress is regained the vehicle can slip back into overdrive for efficient and less fussy travel.We hope that helps answer the question ‘What is What is Overdrive?’!

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