What is the primary purpose of the lock-up clutch in a torque converter?

What is the primary purpose of the lock-up clutch in a torque converter?

• A. To increase slippage
• B. To lock the turbine to the converter shell and eliminate slippage
• C. To increase torque multiplication
• D. To reduce hydraulic fluid flow

Answer: (B)

The main idea is that the lock-up clutch removes the slip inside the torque converter at higher speeds to improve efficiency. In a torque converter, the fluid between the impeller and turbine allows torque to be multiplied when the engine is turning faster than the wheels, but that slip also wastes energy as heat. When the lock-up clutch engages, it creates a direct mechanical link between the pump housing and the turbine, so the engine torque is transmitted almost directly to the transmission input with little to no slip. This greatly reduces heat and improves fuel economy. It’s not about increasing torque multiplication; in fact, locking the converter reduces that multiplication, which is acceptable at cruising speeds where efficiency matters. It also doesn’t reduce hydraulic fluid flow; the fluid is still there to allow the rest of the converter to function, but the slip is eliminated by the lock-up.