Together with the a few-passage torque converter, two passages are useful for transmission oil (ATF) flow with the torque converter and for clutch cooling, while the third passage is employed independently to control the lock and unlock in the clutch. And not using a clutch to lock up the torque https://torqueconverterclutch74195.mdkblog.com/39817792/an-unbiased-view-of-torque-converter-clutch