Third Clutch Exhaust Valve
WARNING: This page is about a different car, the 2009 Cadillac DTS. However, it is still accessible from the selected car via links, so may be relevant.
Spring force holds the third clutch exhaust valve in the downshifted position. The valve allows third clutch fluid from the third clutch piston to exhaust through the valve. Orificed third clutch fluid form the valve is routed back through orifice #3 to checkball #11.