Mitsuman;
Look at the steer_hydraulic pumps "load sensing and priority valve". When steering is actuated, the load sensing pressure connection's oil tank connection is blocked by the orbital, steering control valve, which causes the pressure in the load sensing line to rise. The increase in pressure causes the priority valve to make the entire volume from the steer pump available for the steering. Their location is on the inside of the steer pump (end pump) of the piggy back pump set up.