High Clutch
WARNING: This page is about a different car, the 2013 Subaru Forester, 2012 Subaru Forester, 2011 Subaru Forester, and 2010 Subaru Forester. However, it is still accessible from the selected car via links, so may be relevant.
When the 3rd or 4th gear is selected, hydraulic pressure is applied to the high clutch from the shift valve and pressure regulator valve. The clutch drive and driven plates are pressed together, thus transmitting the engine power from the input shaft to the front planetary carrier through the high clutch hub.
A cover is placed inside the piston, and the space between the piston and the cover is filled with ATF. When the high clutch is not in engagement, the centrifugal force generated in the ATF inside the cover cancels out the centrifugal force generated in the ATF remaining behind the high clutch piston, thus preventing incomplete disengagement of the clutch.