Power Steering Gear
The power steering gear has a recirculating ball system which acts as a rolling thread between the worm shaft and the rack piston. When the worm shaft is turned right, the rack piston moves up in gear.
Turning the worm shaft left moves the rack piston down in gear. The rack piston teeth mesh with the sector gear, which is part of the sector shaft.
Turning the worm shaft turns the sector shaft, which turns the wheels through the steering linkage. The control valve in the steering gear directs the power steering fluid to either side of the rack piston.
The rack piston converts the hydraulic pressure into a mechanical force. If the steering system becomes damaged and loses hydraulic pressure, the vehicle can be controlled manually.