Power Steering Gear: Gear: Operation

Turning of the steering wheel is converted into linear (side-to-side) travel through the meshing of the helical pinion teeth with the rack teeth in the steering gear. This travel pushes and pulls the tie rods to change the direction of the vehicle's front wheels.

Power assist steering provided by the power steering pump is controlled by an open-center, rotary type control valve which directs fluid from the pump to either side of the integral rack piston upon demand.

Road feel is controlled by the diameter of a torsion bar which initially steers the vehicle. As required steering effort increases, as in a turn, the torsion bar twists, causing relative rotary motion between the rotary valve body and the valve spool. This movement directs oil behind the integral rack piston which, in turn, builds up hydraulic pressure and assists in the turning effort.

Manual steering control of the vehicle can be maintained if power steering assist is lost. However, under this condition, steering effort is significantly increased.