While using the a few-passage torque converter, two passages are used for transmission oil (ATF) flow from the torque converter and for clutch cooling, whilst the 3rd passage is utilised independently to regulate the lock and unlock on the clutch. Don't forget, if you suspect a nasty torque converter, in https://torqueconverterclutch42073.blogunteer.com/33226579/about-torque-converter-clutch