2-3 Shift 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 2-3 shift valve in the downshifted position. The 2-3 shift valve prevents drive fluid from entering the third clutch circuit. In the absence of hydraulic pressure in the third clutch circuit, spring force moves the third clutch exhaust valve.