Chapter 69 Steering System Fundamentals

Collapsible steering column

A column that is designed to crumble or slide together when forced forward during a collision

Tilt steering column

A column with a flex joint or U-joint that allows the top half of the column and the steering wheel to be positioned at different angles

Relay rod

Also called a center link, a steel bar that connects the right and left sides of the steering linkage

Center link

Also called a relay rod, a steel bar that connects the right and left sides of the steering linkage

Steering ratio

Also called gearbox ratio or steering gear reduction, is basically a comparison between steering wheel rotation and sector shaft rotation

Gearbox ratio

Also called steering ratio or steering gear reduction, is basically a comparison between steering wheel rotation and sector shaft rotation

Steering damper

An oil filled shock absorber found in some parallelogram linkage arrangements, it is attached between the vehicles frame and the center link

Variable-ratio gearbox

Changes the internal gear ratio as the front wheels are turned from the center position.

Steering gearbox

Changes turning motion into a straight-line motion to the left or right

Tie-rods

Connect the rack with the steering knuckles

Steering linkage

Connects the steering gearbox to the steering knuckles and the wheels

Steering column assembly

Consist of the steering wheel, steering shaft, column, ignition key mechanism, and sometimes a flexible coupling and a universal joint

Rack-and-pinion steering gear

Consists of a pinion shaft, a rack, a thrust spring, bearings, seals, and a gear housing

Integral power steering gearbox

Contains a conventional worm-and-sector gear, a hydraulic piston, and a flow-direction valve

Worm-and-roller steering gearbox

Contains a roller that is mounted on the sector shaft and meshes with the worm gear

Power steering pump

Engine driven and produces the hydraulic pressure for the steering system operation

Tie-rod assemblies

Fastens the center link to the steering knuckles

Rubber dust boots

Fit over the inner ball sockets to keep out dirt and water, as well as to hold in lubricating grease

Constant-ratio gearbox

Has the same gear reduction from full left to full right

Flexible coupling

Helps keep road shock from being transmitted to the steering wheel, also allows for slight misalignment of the steering shaft and steering gear input shaft.

Power steering hoses

High and low pressure, hydraulic, rubber hoses that connect the power steering pump and the integral gearbox or the power cylinder

Power steering fluid reservoir

Holds an extra supply of hydraulic fluid

Spool and rotary valves

Hydraulic control valves used to direct high pressure fluid to either side of the power assist piston and dump low pressure fluid back to the reservoir; used with both worm and rack-and-pinion gearboxes

Steering rack

Long steel bar with teeth along one section; it is the output of a rack and pinion gearbox

Manual tilt column

Makes use of a lever on the steering column to unlock the flex joint so the wheel can be moved up or down

Power tilt column

Makes use of a small electric motor, a control switch, and a gear mechanism to change the steering wheel angle or height

Memory tilt wheels

Makes use of a tilt control module (computer) to "remember" more than one steering wheel position

Recirculating-ball gearbox

Normally used with a linkage steering system, it has small steel balls that circulate between the gear members.

Pinion thrust spring

Preloads the rack-and-pinion gear teeth to prevent excessive gear backlash

Ball sockets

Provide for motion in all directions, allow linkage arms to swivel up and down (for suspension action) and from left to right (for turning)

Toe adjustment sleeve

Provided for changing the length of the tie-rod assembly during wheel alignment

Preload adjusting nut

Provided to set worm shaft bearing preload

Gearbox housing

Provides an enclosure for the other components of the steering gearbox, whether recirculating ball or rack and pinion gearbox

Ball nut

Rides on the ball bearings and the worm gear, it slides up and down as the worm gear rotates

Pinion gear

Rotated by the steering wheel and steering shaft; it is the input of a rack and pinion gearbox

Ball guides

Route extra ball bearings in and out from between the worm and ball nut

Road feel

Slight steering wheel pull caused by road surface

Idler arm

Supports the end of the center link on the passenger side of the vehicle

Steering column

Supports the steering wheel and the steering shaft

Worm shaft

The input gear connected to the steering column shaft, the balls fit and ride in the grooves in the worm gear

Sector shaft

The output gear from the steering gearbox, it transfers motion to the steering linkage

External cylinder power steering system

The power cylinder is not in the gearbox, and commonly bolted to the frame and the center link; the hydraulic control valve may be located in the gearbox or on the steering linkage

Pitman arm

Transfers gearbox motion to the steering linkage

Steering shaft

Transfers turning motion from the steering wheel to the steering gearbox

Parallelogram steering linkage

Type of steering linkage that includes a pitman arm, a center link, an idler arm, ball sockets, and two tie-rod assemblies, it may also include a steering damper.

Steering wheel

Used by the driver to rotate a steering shaft that passes through the steering column

Pressure-relief valve

Used in a power steering system to control maximum oil pressure, it prevents system damage by limiting pressure when needed

Gear lash adjusting screw

Used to set the sector shaft clearance