#9 Checkball (Coast Clutch Feed, Orificed Coast Clutch Feed)
WARNING: This page is about a different car, the 2008 Buick Lucerne. However, it is still accessible from the selected car via links, so may be relevant.
The #9 checkball is located in the valve body, and the checkball is unseated by coast clutch feed. The checkball routes fluid through orifice #7, where the fluid enters the coast clutch circuit. Coast clutch fluid is then routed to the 2-3 shift valve.