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 hold the 2-3 shift valve in the downshifted position. D21 fluid passes through the valve and orifice #10, where the fluid enters the orificed D21Y circuit. Orificed D21Y fluid is then routed to the 3-4 shift valve. D21 fluid also passes through orifice #9, where the fluid enters the coast clutch circuit, and the fluid is routed to the 3-4 shift valve. Coast clutch fluid is then directed to the coast clutch piston, and the fluid applies the clutch.