What effect does the lock-up clutch have in the torque converter's operation?

What effect does the lock-up clutch have in the torque converter's operation?

• A. Increases rotary oil flow in the torque multiplication phase
• B. Provides 100% efficiency between impeller and turbine
• C. Increases vortex oil flow in the coupling phase
• D. Allows a higher stall speed

Answer: (B)

The lock-up clutch’s job is to create a direct mechanical link between the engine side (impeller) and the transmission side (turbine) of the torque converter. When it engages, the fluid coupling slip is eliminated, so power is transferred with almost no energy lost to fluid shear. That’s why this stage is described as providing near 100% efficiency between the impeller and turbine—the torque is transmitted as if it were a solid shaft, rather than through fluid coupling. In normal operation, the torque converter’s early phase relies on fluid slip to multiply torque, but that comes with energy losses from the moving fluid. Engaging the lock-up clutch stops that slip, improving efficiency and reducing heat. It doesn’t increase oil flow in the torque multiplication phase, it isn’t about increasing vortex oil flow, and it doesn’t raise stall speed—the lock-up simply removes slip to transfer power more efficiently.

The lock-up clutch’s job is to create a direct mechanical link between the engine side (impeller) and the transmission side (turbine) of the torque converter. When it engages, the fluid coupling slip is eliminated, so power is transferred with almost no energy lost to fluid shear. That’s why this stage is described as providing near 100% efficiency between the impeller and turbine—the torque is transmitted as if it were a solid shaft, rather than through fluid coupling.

In normal operation, the torque converter’s early phase relies on fluid slip to multiply torque, but that comes with energy losses from the moving fluid. Engaging the lock-up clutch stops that slip, improving efficiency and reducing heat. It doesn’t increase oil flow in the torque multiplication phase, it isn’t about increasing vortex oil flow, and it doesn’t raise stall speed—the lock-up simply removes slip to transfer power more efficiently.