Valve Section

Neutral 

• 1. To the right-hand side of the piston
• 2. To the left-hand side of the piston
• 3. Supply
• 4. Return oil
• 5. Servo oil, free flow

The valve is open when the vehicle's engine is running and there is no steering input. In the open position, none of the ducts to the operating cylinders are blocked. The servo oil circulates freely through the valve.

Steering left 

• 6. Servo oil, low pressure
• 7. Servo oil, high pressure

When the steering wheel is turned to the left and the wheel resistance is so great that the torsion bar inertia is overcome, the steering gear input shaft moves to the left in relation to the worm screw, within the play between the lugs.

With this movement the input shaft stops the free flow through the valve and sends the fluid through the upper feed pipe to the right-hand side of the piston.

As long as the torsion bar is affected by steering input, the oil pressure continues to push the steering rack to the left and servo assistance is obtained. If the steering input reduces, the torsion bar springs back. The valve section then reverts to the center position so that the oil can circulate freely through the valve housing.

Steering right 

• 6. Servo oil, low pressure
• 7. Servo oil, high pressure

The function when turning right is, in principle, the same as to the left. The only difference is that the steering gear input shaft stops the flow of high pressure oil through the return and down through the groove on the inside of the valve and out through the low pressure pipe to the left-hand side of the piston.