Four-Wheel Steering System
Four-Wheel Steering System
The picture shows the layout of the components on one system in current use. As is common with many, if not all aspects of the vehicle, electronic control is now playing a role in four-wheel steering systems. This is used to determine the amount and direction of rear wheel movement.
System Components
Summary Power assistance is used to make steering operation easier. This also improves safety. Two sources of ‘power assistance’ are hydraulic and electric. Hydraulic systems are common but the use of electric systems is increasing. Four- wheel steering systems improve vehicle handling, but are relatively complex and therefore add significant cost to the manufacture of the vehicle.
List THREE ways in which electric motor assisted steering systems operate
Look back over the previous section and write out a list of the key bullet points here:
TOOLS AND EQUIPMENT
Introduction Components will usually be removed, inspected and repaired or replaced when a defect has been diagnosed. Other components are replaced, or stripped and cleaned, at scheduled mileage or time intervals. Refer to the Routine Maintenance Section for details on these items.
Soft Hammers These tools allow a hard blow without causing damage. They are ideal for working
on driveshafts, gearboxes and final drive
Some
components. Some types are made of special hard hammers
contain metal
plastics whereas some are described as
shot to give a
copper/hide mallets. This type has a copper insert ‘dead blow’ on one side and a hide or leather insert on the
other. It is still possible to cause damage however, so you must take care!
Ball Joint Splitter Two types of ball joint splitter are in common use. One type is a simple
forked wedge that is Lever type splitter hammered in between
Wedge type splitter
the joint and the arm. This works well but can damage the joint. If the joint is to be reused, the lever type splitter is preferred. This tool clamps onto the arm and threaded section of the joint. A bolt is tightened, which applies a force to push the joint free.
Jacks and Stands Most jacks are simple hydraulic devices. Remember to make sure
the safe working load After jacking a vehicle (SWL) is not exceeded.
Always use stands
Ensure that any faults with equipment such as this are reported immediately. Axle stands must always be placed under the vehicle supporting the weight – before work is carried out.
Ramps and Hoists Many types of ramp or hoist are available ranging from large four-post wheel-free types through two Four post lift Single post
post and smaller single-post lifts, to lift
in use Two
post lift
portable devices. These large items should be inspected regularly to ensure
they are safe. Portable lift
Transmission Jack If a complete gearbox has to
be removed, it is likely to be heavy! A transmission jack has attachments that allow you to support the This jack will
gearbox and lower it safely. The equipment is support a
gearbox
hydraulically operated just like an ordinary jack. Often, the height can be set by using a foot pedal, which leaves both hands free for positioning the unit.
Pullers Removing some bearings is difficult without a proper puller. For internal bearings, the tool has small legs External puller Hydraulic
and feet that hook under the bearing. A puller threaded section is tightened to pull out
the bearing. External pullers hook over Internal puller the outside of the bearing and a Slide hammer
screwed thread is tightened against the shaft. A slide hammer is a form of puller. It consists of a steel rod over which a heavy mass slides. The mass is ‘hammered’ against a stop, thus applying
a pulling action.
Air Tools The whole point of power tools is that they do the work so you don’t have to! Air guns produce a
Air gun
Air drill
‘hammer’ action. Because of this, impact sockets should be used. Normal sockets can shatter under this load. It is
Air ratchet
Air chisel
important to remember that air tools need lubricating from time to time. Air ratchets are very useful for removing or fitting nuts and bolts. However, it is possible to over tighten if care is not taken. Air tools can be very powerful and will trap your hands!
Grease Gun A grease gun is a simple device that pumps grease under pressure. A special connector fits onto a grease nipple. Some types are air operated but this one is pump action.
Look back over the previous section and write out a list of the key bullet points here:
ROUTINE MAINTENANCE
Scheduled Servicing Scheduled service requirements are often quite simple but still important. Systems should be checked for correct operation. Adjustments, repairs or replacements are then made if required. The servicing requirements for the driveshafts are limited but none-the-less important.
Non-Routine Work When carrying out routine maintenance, some non-routine work may be found. This should be reported to the driver or owner of Damaged
the vehicle before expensive repairs are carried steering
gaiter
out.
Worksheet Service manual
Gaiters
Rack
steering system. Servicing steering systems is a simple
Ball joints
Column
task. However, before starting work carry out the basic checks. These are described in the ‘Check Steering Components’ worksheet. It is important to check for damage, security, wear and leaks. Repair any faults found after reporting them to the customer.
Manual Steering System Check and top up the steering gearbox oil if appropriate. Check the operation of column adjustment if fitted. Lubricate grease points on swivel
Greasing swivel joints
joints/kingpins using a grease gun. Lubricate is only necessary on
older cars