Abstract: A vehicle has a primary drive pump in communication with driven pumps associated with each wheel for driving the vehicle as hydraulic fluid is ported to the wheel pumps through a by-pass valve. The pumps are similarly designed with each including a rotor co-axially mounted within a fixed stator defining an annular pump chamber when fluid entering an intake opening moves against gradually extending vanes provided on the rotor. The fluid exits through a discharge opening in the stator, and the vanes are designed to be fully retracted at a position between the openings and gradually extended so as to fully extend after moving beyond the intake opening. Also, the vanes gradually retract as they approach the discharge opening.