Along with the 3-passage torque converter, two passages are used for transmission oil (ATF) movement from the torque converter and for clutch cooling, even though the 3rd passage is applied independently to regulate the lock and unlock of your clutch. The torque converter requires to create up force inside it https://torque-converter-clutch21851.bloggerchest.com/34170816/facts-about-torque-converter-clutch-revealed