Filtration for integrated tractor hydraulic system

A hydraulic system including, a fluid reservoir, a constant displacement pump, a fluid supply filter connected between the low pressure side of said constant displacement pump and said reservoir, at least one hydraulic fluid motor connected to the high pressure side of said constant displacement pump, a variable displacement pump including a pressure compensator, at least one hydraulic fluid actuator connected to the high pressure side of said variable displacement pump, means connecting said pressure compensator to said hydraulic fluid actuator to vary the displacement of said variable displacement pump responsive to load pressures on said hydraulic fluid actuator, a fluid return filter connected on one side to the return side of said hydraulic fluid motor and to the return side of said hydraulic fluid actuator and on the other side to the low pressure side of said variable displacement pump for filtering returned hydraulic fluid supplied to said variable displacement pump, a surge tank in communication with said fluid reservoir, a hydraulic conduit means connected to said surge tank and connected between said return filter and said variable displacement pump to provide a filtered reserve supply of hydraulic fluid to compensate for variations of flow rate between said return filter and said variable displacement pump.