Patent ID: 7383683

Claim:
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.