3rd Gear Band (B4) Servo Piston Assembly
WARNING: This page is about a different car, the 2009 Pontiac Torrent and 2009 Chevrolet Equinox. However, it is still accessible from the selected car via links, so may be relevant.
3rd gear band apply (46) fluid is routed to the 3rd gear band servo piston assembly which applies the 3rd gear band assembly to hold the 4-5 clutch drum assembly.