Which statement best describes the effect of the lock-up clutch on the torque path?

Which statement best describes the effect of the lock-up clutch on the torque path?

• A. Increases efficiency through fluid coupling
• B. Provides 100% efficiency between impeller and turbine
• C. Adds more fluid flow during coupling
• D. Increases stall speed

Answer: (B)

When the lock-up clutch engages, it mechanically connects the impeller and turbine, removing the slip that normally comes from fluid coupling. That makes the power transfer between those two components essentially direct, so the efficiency of the torque path reaches (and is treated as) 100% in this state. This is why engaging the lock-up clutch reduces energy loss as heat and improves cruising efficiency. The other ideas don’t fit because the lock-up doesn’t increase fluid flow, and it doesn’t raise stall speed—the clutch’s job is to reduce slip at higher speeds, not to boost low-speed torque multiplication or fluid flow dynamics.

When the lock-up clutch engages, it mechanically connects the impeller and turbine, removing the slip that normally comes from fluid coupling. That makes the power transfer between those two components essentially direct, so the efficiency of the torque path reaches (and is treated as) 100% in this state. This is why engaging the lock-up clutch reduces energy loss as heat and improves cruising efficiency. The other ideas don’t fit because the lock-up doesn’t increase fluid flow, and it doesn’t raise stall speed—the clutch’s job is to reduce slip at higher speeds, not to boost low-speed torque multiplication or fluid flow dynamics.