CH46 steering systems STUDENT VERSION rev

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Chapter 46

Steering Systems

Manual Steering Systems

• Steering system is composed of three major subsystems:

– Steering linkage

– Steering gear

– Steering column and wheel

Steering Linkage

• Applies to the pivots and connecting parts between the steering gear and steering arms

• Transfers motion from the steering gear

• The type of front suspension greatly determines

the type of linkage

Parallelogram Steering Linkage

• Once the most common type

• Used with the recirculating ball gearbox

• Can be placed in front or behind the front

suspension

• Provides good steering geometry

• Road vibrations and impact forces cause wear and looseness

Parallelogram Steering

Rack-and-Pinion Steering Linkage

• Lighter and has fewer components than the

parallelogram linkage

• The rack performs as steering gear and center link

• Tie-rods are the only linkage used

• Provides better road feeling but can transmit more road shock

Rack-and-Pinion Steering System

– Worm and roller

– Rack and pinion

Recirculating Ball

• Found in larger cars,

trucks and vans

• The ball nut moves the

worm gear which moves

the sector shaft

Steering Wheel and Column

• Provides the force to turn the steering gear

• Since 1968, all columns are collapsible

• Houses the driver side air bag

• May have tilt and/or telescoping features

• Houses many of the driver operated switches and sometimes the transmission shifter

Power Steering Systems

• Reduce driver effort

Power Steering System Types

Integral Piston System

Power-Assisted Rack and Pinion

Power Steering Pump Types

• Roller

• Vane

• Slipper

• Gear

Flow Control and Pressure Relief Valves

• Necessary due to

engine speed

variations

• At higher speeds the

pump can deliver more

flow than is needed

Power Steering Gearbox

• Nearly the same as a manual gearbox

• Rack and pinion:

– A rotary valve changes fluid flow

• Integral piston power steering:

– A spool valve and power piston are used

– The spool valve directs oil to the left or right power chamber

– The spool valve operates by a small torsion bar

Power Steering Hoses

• Transmit fluid from the pump to the gearbox and back to the pump

• Must handle pressures up to 1500 psi

• Subject to pressure and pulsations from the pump

• Must be able to withstand temperatures of up to 300ºF (150ºC)

Electronically Controlled Power-Steering Systems

• EPS systems provide increased assist at low speeds and decreased assist at higher speeds

• The amount of fluid flow is controlled by a

pressure control valve

• Uses input from VSS

Common Steering System Complaints

Visual Inspection

• Check the tires first:

– Pressure, size, construction, wear, damage, defects, runout, and balance

• Power steering drive belt

• Power steering fluid

• Fluid leaks

Power Steering Leak Points

Power Steering Fluid

• Can be checked hot or cold

• Most reservoir caps have a dipstick

• Some manufacturers recommend specific power steering fluids Some recommend a type of ATF

• Check color, odor, and for signs of metal content

Pitman Arm

• Most heavily stressed

point in the system

• Check for looseness

• Removal requires a

pitman arm puller

Center Link

• A worn or damaged center link can cause end shimmy, pull, changes in toe, and tire wear

front-Tie-Rod Assembly

• Worn tie-rods result in incorrect toe, scalloped and scuffed tires, wheel shimmy, understeering, noise, and tire squeal on turns

Dry Park Check

• Performed with full weight on the wheels

• Have an assistant rock the steering wheel back and forth

• Check for looseness in the idler arm, center link, tie rods, and pitman arm

Turning Effort

• Use a pull scale to read the

actual force necessary to

turn the wheel

• Compare to specifications

• Inspect entire steering

system if excessive before

performing a pressure test

Rack and Pinion Steering

• Has only four wear points - the tie-rod ends

• Check power units for power steering fluid leaks

• Inspect mountings, tie rods, bellows, steering

couplings, and gearbox adjustment

Steering Gear Adjustments

• Carefully inspect steering and suspension

components, wheel alignment, wheel balance, and tire pressure

• Wormshaft preload and sector gear preload may be adjustable

Steering Wheel

• Place front wheels straight ahead

• Disconnect battery negative cable

• Remove steering pad and retaining nut

• Place alignment marks on shaft and wheel

• Disconnect electrical connectors

• Use correct puller and remove wheel

Bleeding the System

• Performed after replacing any system hydraulic part

• Follow service manual procedures

• A vacuum pump can be used to purge air

• Often running the engine and turning the steering from stop to stop will remove the air

Hoses and Lines

• Inspect for leaks, dents, sharp bends, cracks, and swelling

• Use exact replacements

• Do not attempt to patch or repair

• Ensure lines and hoses do not rub against other components

Power Steering Pump

• Pulleys may be replaced if bent, cracked, or worn

• Some require special pullers and installation tools

• Flow control valves and pressure relief valves may

be replaceable

Four-Wheel Steering Systems

Air Bag Safety Precautions

• Always wear safety glasses

• Follow the manufacturer’s procedure for

disarming the system before servicing

• Never probe the connectors on the air bag module

• Always carry an air bag module with the trim

facing away from your body

Air Bag Safety Precautions

(Cont’d)

• Never set a live air bag module down with the trim cover facing down

• Wash your hands with soap and water after

working around a deployed air bag