Abstract: A hydraulic drive unit having a center section for a hydraulic pump and hydraulic motor mounted in a casing. The center section includes a cylindrical protuberance for locating the center section in the casing, and at least one fastener opening formed in the center section for receiving a fastener engaged to the casing. The drive unit may also include a pair of flat surfaces formed on the center section and adapted to mount with features in the casing, and a bypass shaft extending into the casing and at least partially disposed in the center section.

Abstract: A hydraulic drive unit having a center section for a hydraulic pump and hydraulic motor mounted in a casing. The center section includes a cylindrical protuberance for locating the center section in the casing, and at least one fastener opening formed in the center section for receiving a fastener engaged to the casing. The drive unit may also include a pair of flat surfaces formed on the center section and adapted to mount with features in the casing, and a bypass shaft extending into the casing and at least partially disposed in the center section.

Abstract: 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.

Abstract: A hydraulic drive device including a center section for rotatably mounting a hydraulic pump and hydraulic motor on respective running surfaces. The center section further includes a pair of ports connecting the running surfaces, where the ports are not located in the same plane but are rather offset from one another with respect to the pump running surface, so that one of the ports is closer to the pump running surface than the other port.

Abstract: A hydraulic drive device including a center section for rotatably mounting a hydraulic pump and hydraulic motor on respective running surfaces. The center section further includes a pair of ports connecting the running surfaces, where the ports are not located in the same plane but are rather offset from one another with respect to the pump running surface, so that one of the ports is closer to the pump running surface than the other port.

Abstract: A pair of zero-turn, hydrostatic transaxles (HZTs) that may be joined to form an integrated, zero-turn, hydrostatic transaxle. Each of the hydrostatic transaxles are further comprised of a casing carrying a hydraulic pump driven by an input shaft, a hydraulic motor driven by a the hydraulic pump through porting contained within a center section, and an axle shaft driven by the hydraulic motor. The hydrostatic transaxles are joined along an interface extending generally perpendicularly to the axle shafts.

Abstract: An expansion chamber for a hydrostatic transaxle to provide for expansion of the hydraulic oil during operation of the transaxle, where the expansion chamber is formed as part of the housing inside the main sump by ribs or other members extending from the housing and is closed by a cap to form a sealed chamber. A siphon tube may be secured to the cap or integrally formed therein, or formed by additional cast ribs or similar features formed into the housing and also sealed by the cap.

Abstract: A pair of zero-turn, hydrostatic transaxles (HZTs) that may be joined to form an integrated, zero-turn, hydrostatic transaxle. Each of the hydrostatic transaxles are further comprised of a casing carrying a hydraulic pump driven by an input shaft, a hydraulic motor driven by a the hydraulic pump through porting contained within a center section, and an axle shaft driven by the hydraulic motor. The hydrostatic transaxles are joined along an interface extending generally perpendicularly to the axle shafts.

Abstract: A center section for a hydraulic pump and motor mounted in a transaxle casing. The center section has a protuberance formed thereon, a pair of flat surfaces separate from the protuberance and at least one fastener opening formed in the center section for receiving a fastener engaged to the casing. The protuberance is adapted to mate with a center section locator formed in the casing to establish an X-Y orientation for a central axis while the fastener provides a Z-axis locator for the center section.

Abstract: An expansion chamber for a hydrostatic transaxle to provide for expansion of the hydraulic oil during operation of the transaxle, where the expansion chamber is formed as part of the housing inside the main sump by ribs or other members extending from the housing and is closed by a cap to form a sealed chamber. A siphon tube may be secured to the cap or integrally formed therein, or formed by additional cast ribs or similar features formed into the housing and also sealed by the cap.

Abstract: A pair of substantially mirror image, zero-turn, hydrostatic transaxles (HZTs) that may be joined to form an integrated, zero-turn, hydrostatic transaxle. The control arm and brake mechanism associated with the HZTs can be mounted on either the inboard or outboard side of the HZT casing. In one embodiment, an integrated, inboard brake mechanism is provided for the joined HZTs.