Types of Bearing
Types of Bearing
There are two main types of bearing used inn rear wheel hubs.
These are ball bearings Roller bearing
Ball bearing
and roller, or tapered roller bearings.
Rear Wheel Bearings Axle shafts transmit drive from the differential to the rear wheel hubs. An axle shaft has to withstand:
Torsional stress due to driving and braking forces Shear and bending stress due to the weight of the vehicle Tensile and compressive stress due to cornering forces.
A number of bearing layouts are used, depending on application, to handle these stresses.
Semi Floating Shown here is a typical axle mounting used on many rear wheel drive cars.
A single bearing is used, which is mounted in the axle casing. With this design, the axle
Wheel bearing –
shaft has to withstand all the operating Semi floating forces. The shaft is therefore strengthened
and designed to do this. An oil seal is incorporated because oil from the final drive can work its way along the shaft. The seal prevents the brakes being contaminated.
Three Quarter Floating The three quarter floating bearing shown here reduces the main
shear stresses on the axle shaft but the other stresses remain. The bearing is mounted on
Wheel bearing –
the outside of the axle tube. An oil seal is Three Quarter
floating
included to prevent the brake linings from being contaminated.
Fully Floating Fully floating systems are generally used on heavy, or off-road vehicles. This is because the stresses on these applications are greater. Two widely spaced
Wheel bearing –
bearings are used, which take all the loads, Fully floating other than torque, off the axle shaft. Bolts or
studs are used to connect the shaft to the wheel hub. When these are removed, the shaft can be taken out without jacking up the vehicle.
Front Wheel Bearings Front hubs on rear wheel drive cars consist of two bearings. These
are either ball or tapered
Front hub with ball
Front hub with
roller types. The roller types bearings
tapered roller
are generally used on earlier bearings vehicles. They have to be adjusted by tightening the hub nut and then backing it off by about half a turn. The more modern hub bearings, known as contact type ball races, do not need adjusting. This is because the hub nut tightens against a rigid spacer. This nut must always be set at
a torque specified by the manufacturer.
Summary The most common systems for rear wheel drive cars are semi floating rear
bearings at the rear, and twin
Front hub
Rear hub
ball bearings at the front. The front bearings are designed to withstand side forces as well as vertical loads.
State the two main types of bearing used in rear wheel hubs
Look back over the previous section and write out a list of the key bullet points here:
FRONT WHEEL DRIVE BEARINGS
Introduction Wheel bearings must allow smooth rotation of the wheel but also be able to withstand high stresses such as when cornering. Front wheel drive arrangements must also allow the drive to be transmitted via the driveshafts.
Front Bearings The front hub works as an attachment for the suspension and steering as well as supporting the bearings. It supports the weight of the vehicle at the front, when still or moving. Ball or roller bearings
Front hub and bearings
are used for most vehicles with specially shaped tracks. This is so the bearings can stand side loads when cornering. The bearings support the driveshaft as well as the hub.
Rear Bearings The stub axle, which is solid-mounted to the suspension arm, fits in the centre of two bearings. The axle supports the weight of the vehicle at the rear, when still or moving. Ball bearings
Rear hub and bearings
are used for most vehicles with specially shaped tracks for the balls. This is so the bearings can stand side loads when cornering. A spacer is used to ensure the correct distance between, and pressure on, the two bearings.
Summary The hub and bearing arrangement on the front, of a front wheel drive car, must bear weight, withstand driving forces and support the driveshaft. The rear hub and bearings must support the vehicle and withstand side forces.
Describe the function of front wheel hub.
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.
Recommended Procedures The descriptions provided in this section deal with the components for individual replacement, rather than as a part of other work. Always refer to a workshop manual before starting work. You will also need to look for the recommended procedure, special tools, materials, tightening sequences and torque settings. Some general and specific tools and pieces of equipment are described on the following screens.
General Toolkit General tools and equipment will be required for most tasks. As your career develops
you will build a collection of tools and equipment.
Snap-on tools
Look after your tools and they will look after you!
Torque Wrench A good torque wrench is an essential piece of equipment. Many types are available but all work on a similar principle. Most are A torque
set by adjusting a screwed cylinder, which forms wrench is a
useful tool
part of the handle. An important point to remember is that regular calibration is essential to ensure it remains accurate.
Air Guns The whole point of power tools is that they do the work so you don’t have to! Most air guns have an aluminium housing. This material is
Wheel gun in
lightweight but gives long life. Air guns produce a use ‘hammer’ action. Because of this, impact sockets
should be used. Normal sockets can shatter under this load. It is important to remember that air tools need lubricating from time to time.
Jacks and Stands Most jacks are simple hydraulic devices. Remember to make sure the safe working load (SWL) is not exceeded. Ensure that any faults Always use
with equipment such as this are reported stands after
jacking a
immediately. Axle stands must always be placed
vehicle
under the vehicle supporting the weight – before work is carried out.
Ramps and Hoists Many ramps are available ranging from large four-post wheel-free types to smaller single-post lifts. These large items should be
Four post lift
inspected regularly to ensure they are safe. in use
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.
Bearing Puller Removing some bearings is difficult without a proper puller. For internal bearings, the tool has small legs and feet that hook under the bearing. A threaded section is
Internal and external bearing pullers
tightened to pull out the bearing. External pullers hook over the outside of the bearing and a screwed thread is tightened against the shaft.
Air Ratchet These tools are very useful for removing or fitting nuts and bolts. However, it is possible to over tighten if care is not taken. Air
These tools
tools can be very powerful and will trap your hands! are very
useful
Take adequate precautions at all times.
Slide Hammer A slide hammer is a form of puller. It consists of a steel rod over which a heavy mass slides. Th e mass is ‘hammered’ against a stop, thus This tool is applying a pulling action. The clamp end of the tool useful for
removing
can screw either into, or onto, the component.
halfshafts
Alternatively, puller legs with feet are used to grip under the sides of the component.
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
Some older
operated but the one shown here is a simple pump UJs can be
lubricated
action type.
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 important. Systems should be checked for correct operation. Adjustments, repairs or replacements are then made if required. The particular servicing requirements for driveshafts are limited but none-the-less essential.
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 CV
the vehicle before expensive repairs are carried gaiter out.
Worksheet Service rear wheel drive propshaft.
This task would normally be carried out as part of a general vehicle service and inspection. However, it may be necessary to check the propshaft at other times. Apply the handbrake and raise the vehicle on a hoist. Make sure the area is well lit so that you can see details. Take care if the exhaust is still hot.
Propshaft The first task is to check the propshaft for security and signs of damage. Make sure that any balance weights are secure. Look at the
Checking the
gearbox output seal where the propshaft sliding universal
joints
joint fits, and make sure it is not leaking. If the general area under the vehicle is oily, it may be necessary to steam clean it first.
Universal Joints Check all the universal joints (UJs) for signs of leakage. If grease is leaking, this may be a sign that the UJ is overheating and in
Grease gun
need of replacement. Some types have a grease point fitted. If this is the case, use a grease gun to pump new grease into each. Clean off any excessive grease. Finally, check all mounting bolts for security.
Worksheet Service front wheel drive
Driveshaft
driveshafts. This task would normally be carried out as part of a
general vehicle service and inspection. However, it may be necessary to check the driveshafts at other times. Apply the handbrake and raise the vehicle on
a hoist. Make sure the area is well lit so that you can see details. It is particularly important to check the area around the rubber gaiters.
Driveshafts The first task is to check driveshafts for security and signs of damage. Make sure that any balance weights and dampers are secure. The
Driveshaft
dampers are simple rubber components, if fitted. and CV gaiters
in position
Check for oil leaks from the final drive output seals. Clean the area first and then check for clean oil. It may be necessary to take the vehicle on a road test, to show up any problems.
Constant Velocity Joints Take particular care to check constant velocity joint gaiters/boots for signs of leakage. Look for signs of black coloured
Checking the
greas gaiters e. It is possible for the strap or ‘cable tie’ that holds the gaiter, to come loose. Replace
gaiters if cuts or any other damage is evident. If grease has been lost, repack the joint with the correct type. Clean off any excess from the driveshaft and surrounding area. Finally, check the main driveshaft nut and any other flange bolts for security.
Summary Safety of all road users and pedestrians is essential. Reliable operation of the vehicle is also important. The condition of all systems is therefore Safety is
vital. Carry out a check at all service intervals. important
Look back over the previous section and write out a list of the key bullet points here:
DRIVELINE – CUSTOMER CARE Regular Checks Regular servicing is vital for a customer’s
safety. Carry out checks at all services and report your findings safety. Carry out checks at all services and report your findings
Vehicle Condition Respect your custo mer’s vehicle and take precautions to keep it clean. Repairing or checking some systems, is likely to involve you working under the vehicle, and then sitting in the driver’s seat. Use seat covers and ensure the steering wheel is clean when you have finished.
Describing Noise Driveline problems often result in unusual noises from the vehicle as it is used. Noise is very difficult to describe! However, the following screen describes some useful terms. These may be useful when discussing problems with your colleagues or customers.
Noise ‘Howling’ or ‘whining’, tends to be a noise associated with gears. It can occur at various speeds and driving conditions, or it can be continuous. ‘Chuckle’ is a rattling noise that sounds like a stick held against the spokes of a spinning bicycle wheel. It usually occurs while decelerating. ‘Knock’ is very similar to ‘chuckle’ though it may be louder and occurs on acceleration or deceleration.
Causes of Noise Clicking, popping or grinding noises may noticeable at low speeds and be caused by:
• Inner or outer CV joints worn (often due to lack of lubrication so
check for split gaiters) • Loose driveshaft
• Another component contacting a drive shaft
• Damaged or incorrectly installed wheel bearing, brake or suspension components.
Vibration The following faults may cause vibration at normal road speeds:
• Out-of-balance wheels • Out-of-round or damaged tyres. • The following may cause shudder or vibration during acceleration: • Damaged powertrain/drivetrain mounts • Excessively worn or damaged, outboard or inboard, CV joints.
Summary A customer, who is kept informed and treated with respect, will return and keep you in a job! Explain things to a customer when asked – it will be appreciated.
FINAL DRIVE AND DIFFERENTIAL
FINAL DRIVE
Introduction Because of the speed at which an engine runs, and in order to
produce enough torque at the road
Front wheel
Rear wheel
wheels, a fixed gear reduction is final drive required. This is known as the final
final drive