Along with the a few-passage torque converter, two passages are used for transmission oil (ATF) flow throughout the torque converter and for clutch cooling, while the 3rd passage is used independently to control the lock and unlock in the clutch. A torque converter is typically made of 4 main parts: https://finnixird.dailyblogzz.com/34541122/not-known-factual-statements-about-torque-converter-clutch