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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 offse

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.

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What is claimed is: 1. A center section for a hydraulic drive device including a hydraulic pump and hydraulic motor, the center section comprising: a pump running surface on which the pump is disposed, comprising first and second surface ports formed thereon for communication with the pump, the pum

What is claimed is: 1. A center section for a hydraulic drive device including a hydraulic pump and hydraulic motor, the center section comprising: a pump running surface on which the pump is disposed, comprising first and second surface ports formed thereon for communication with the pump, the pump running surface being coplanar with a first plane; a motor running surface on which the motor is disposed, comprising third and fourth surface ports formed thereon for communication with the motor; a first port passage connecting the pump running surface to the motor running surface, wherein the first port passage comprises a first end region in communication with the first surface port, a second end region in communication with the third surface port and a first middle segment between the first and second end regions of the first port passage, the first middle segment extending generally parallel to and offset from the first plane; a second port passage connecting the pump running surface to the motor running surface, where the second port passage comprises a first end region in communication with the second surface port, a second end region in communication with the fourth surface port and a second middle segment between the first and second end regions of the second port passage; wherein a second plane that is parallel to and offset from the first plane passes through the first middle segment of the first port passage and the first and second end regions of the second port passage, and the second middle segment of the second port passage is offset from the second plane, and wherein a third plane that is generally parallel to the first and second planes passes through at least part of the second middle segment of the second port passage, and the second plane is between the first and third planes. 2. The center section of claim 1, wherein the pump running surface is generally perpendicular to the motor running surface. 3. The center section of claim 1, wherein the second plane intersects the third and fourth surface ports formed on the motor running surface. 4. A center section for a hydraulic drive device, the center section comprising: a pump running surface for a rotating hydraulic pump, the pump running surface being generally coplanar with a first plane; a motor running surface for a rotating hydraulic motor; a first port passage formed in the center section for connecting the pump running surface to the motor running surface and comprising at least a first segment located between two end regions, wherein a second plane that is generally parallel to and offset from the first plane intersects the first segment; and a second port passage formed in the center section for connecting the pump running surface to the motor running surface and offset from the first port passage so that the first and second port passages do not intersect, wherein the second port passage is longer than the first port passage and comprises first and second end regions and a middle segment, and wherein at least a portion of the first and second end regions are located in the second plane, and at least a portion of the middle segment intersects a third plane that is generally parallel to and offset from the first and second planes. 5. A center section for a hydraulic drive device, the center section comprising: a pump running surface for a rotating hydraulic pump, the pump running surface being generally coplanar with a first plane; a motor running surface for a rotating hydraulic motor; first and second port passages formed in the center section for connecting the pump running surface to the motor running surface, wherein the first port passage comprises at least a first segment, and a second plane that is generally parallel to and offset from the first plane intersects the first segment; and the second port passage is longer than the first port passage and comprises first and second end regions and a middle segment, and wherein at least a portion of the first and second end regions are located in the second plane, and a third plane that is generally parallel to and offset from the first and second planes intersects the middle segment, and wherein the first segment of the first port passage is closer to the pump running surface than the middle segment of the second port passage. 6. A center section for a hydraulic drive device, the center section comprising: a pump running surface for a rotating hydraulic pump, the pump running surface being generally coplanar with a first plane; a motor running surface for a rotating hydraulic motor; first and second port passages formed in the center section for connecting the pump running surface to the motor running surface, wherein the first port passage comprises at least a first segment, and a second plane that is generally parallel to and offset from the first plane intersects the first segment; and the second port passage is longer than the first port passage and comprises first and second end regions and a middle segment, and wherein at least a portion of the first and second end regions are located in the second plane, and a third plane that is generally parallel to and offset from the first and second planes intersects the middle segment; and a fourth plane that is perpendicular to the first, second and third planes intersects both the first segment of the first port passage and the middle segment of the second port passage. 7. The center section of claim 6, wherein the pump running surface is generally perpendicular to the motor running surface. 8. The center section of claim 6, wherein the second plane intersects openings formed on the motor running surface. 9. A center section for a hydraulic drive device including a hydraulic pump and hydraulic motor, the center section comprising: a pump running surface on which the hydraulic pump is disposed, the pump running surface comprising first and second surface ports formed thereon for communication with the pump; a motor running surface on which the hydraulic motor is disposed, the motor running surface comprising third and fourth surface ports formed thereon for communication with the motor, wherein the third and fourth surface ports are intersected by a first plane that is offset from and parallel to the pump running surface; a first port passage connecting the first surface port and the third surface port, the first port passage comprising a first middle segment extending generally in the first plane; a second port passage connecting the second surface port and the fourth surface port, the second port passage comprising a second middle segment, wherein at least a portion of the second middle segment is offset from the first plane; wherein a second plane, perpendicular to the first plane, intersects both the first and the second middle passages. 10. The center section of claim 9, wherein the first plane lies between the second middle segment and the pump running surface. 11. The center section of claim 9, wherein the motor running surface is parallel to the second plane.