US Patent 7350633 Apply piston for a power transmission

An apply piston for a torque-transmitting mechanism in a power transmission includes a first circumferential periphery and a second circumferential periphery radially inward of the first circumferential periphery and axially displaced therefrom. The apply piston has a generally radially-extending face between the two peripheries. The two peripheries and the radially-extending face cooperate with a transmission case to form a fluid-filled chamber that is selectively expandable to direct fluid force to the piston for engagement of the torque-transmitting mechanism.