US Patent 7971435 Hyrdaulic transmission

A hydraulic transmission comprises a hydraulic pump and a hydraulic motor, which are mounted onto a center section to be fluidly connected to each other through a closed fluid circuit formed in the center section. A neutral valve is connected to the closed fluid circuit. The neutral valve is fitted into an outward opened end of a vertical slanted oil hole of the closed fluid circuit. Alternatively, the neutral valve is fitted into an outward opened end of a straight oil hole having an opposite outward opened end into which a charge check valve is fitted.