The 4xxx models feature a servo system controlled by a gear pump connected to the steering wheel. There may also be a typical orbitrol that controls the actuator. It is then a closed system without Ls. In the pressure line P, the pump maintains constant pressure, so the supply and drain are connected via tees. For this system I use a special valve with a 2-way compensator which helps in smooth control. We installed it on these tractors, it worked very well.
