The role of the torque converter: when the engine idle running, torque converter between the engine and gearbox is equivalent to a did not engage the clutch. (2) increase torsion effect. With "high pump wheel speed" + "low turbine speed" to cooperate, to increase the torque, resulting in a larger starting, driving torque. (3) the hydraulic coupling. In not idle or not under the condition of starting, it is equivalent to a hydraulic coupler, the engine torque to transmission. (4) locking function. When the turbine speed up and constant speed pump, in lockup clutch hang, torque converter to 1:1 to pass to the gearbox of engine power. The torque converter is used to install torque converter shell casings.