- The torque convertor steps up the engine torque when starting and accelerating. This permits the use of a three-speed gearbox only. - Connected to an gear train, it enables the classical clutch mechanism to be eliminated (since the pinions should not be engaged, it is not necessary to them when changing gear). - This assembly ensures smooth transmission of the engine power without jerking. This prolongs the life of the parts. - For the driver the advantages are : - extra comfort and less fatigue since he is not preoccupied with changing gear and the clutch pedal is eliminated.