US Patent 8418452 Hydrostatic transaxle

A hydraulic drive device including a hydraulic pump and hydraulic motor disposed in a casing and driving an axle having an interior end disposed inside the casing and abutting against an interior surface of the casing to prevent an inward axial movement of the axle shaft. The device further includes an expansion chamber formed in the casing by a plate having a generally flat portion extending generally perpendicular to the plate to form a thumb stop and an indentation sized to accept a human finger to assist during installation of the plate.