The steering rack is supported at the pinion end, by being sandwiched between the pinion and a spring-loaded, rack guide yoke. This spring-loaded yoke ensures free play is eliminated between the gears, while still allowing for relative movement.
The rack is supported at the other end in the rack housing, or tube, by a bush, normally of nylon. Nylon is used because it has a low coefficient of friction, and low wear rates.
The pinion is supported by 2 bearings in the rack housing. These bearings are pre-loaded to keep the pinion in the correct position, relative to the rack, and to eliminate free play.
A rack-and-pinion steering box is normally lubricated by grease.
Each end of the rack is protected from dirt and water by a flexible, synthetic, rubber bellows, attached to the rack housing and to the tie rod. The bellows extends and collapses, as the tie-rods move away from, and towards the housing, as the rack moves.
On some vehicles, both bellows are interconnected by a tube so that as the steering wheel is moved from side to side, air is transferred from the collapsing bellows side to the expanding bellows side.
Rack-and-pinion type steering gears are used because their construction makes them compact and light-weight.
Their steering response is very sharp, because the rack operates directly on the steering knuckle.
And there is very little sliding and rotation resistance, which gives lighter operation.
Source: CDX Global
