lower half of the pump the other end of bore 74 terminates at the motor end in a radially extending port 88 that is similar in configuration to port 87 port 88 is in communication with the chambers formed within cylinders 78 when said cylinders and associated pistons are moving in the lower half of the motor a passageway 89 communicates at one end to bore 57 and then passes through spacer housing 14 and its central portion 22 and continues axially through pintle shaft 23 passageway 89 extends through the end of pintle shaft 23 and abuts the end of output shaft 24 externally connected to housing 11 is a combination shuttle and high pressure relief valve such as that described in the patent application entitled 34 combination shuttle and high pressure relief valve 34 being filed concurrently herewith and having the same inventor as the present application such valve structure communicates with both passages 73 and 74 through ports not shown as well as with sump chamber 42 in addition external controls may be provided to hydraulically position race 51 within housing pump 12 in order to regulate the pumping output of the pump the motor has its race 82 permanently positioned in eccentric relation to motor rotor 76 whereby its speed and direction are directly determined by the output of the pump the pump and motor operate in the conventional manner of such hydrostatic systems specifically the housing 11 and associated controls and valving mechanisms are filled with hydraulic fluid input shaft 31 is powered by an extended motor to rotate the.