start

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OBJECTIVES:
After studying Chapter 73, the reader should
be able to:
• Prepare for Suspension and Steering (A4) ASE
certification test content area “C” (Related
Suspension and Steering Service).
• Discuss the various types, designs, and parts
of automotive antifriction wheel bearings.
• Describe the symptoms of defective wheel
bearings.

Continued
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OBJECTIVES:
After studying Chapter 73, the reader should
be able to:
• Explain wheel bearing inspection procedures
and causes of spalling and brinelling.
• List the installation and adjustment procedures
for front wheel bearings.
• Explain how to inspect, service, and replace
rear wheel bearings and seals.

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KEY TERMS:
antifriction bearings • axial load

ball bearings • brinelling

cage • C-lock axle • cone • cup

dynamic seals

garter spring • GC-LB • grease • grease seal

inner ring

National Lubricating Grease Institute (NLGI)

Continued
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KEY TERMS:
outer ring

radial load • retainer plate-type axle • roller bearings

spalling • static seal

tapered roller bearings

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ANTIFRICTION BEARINGS
Bearings allow the wheels of a vehicle to rotate and still support
the weight of the entire vehicle. Antifriction bearings use rolling
parts inside the bearing to reduce friction. Four styles of rolling
contact bearings include ball, roller, needle, and tapered roller
bearings, as shown here.

Figure 73–1 Rolling contact bearings include (left to

right) ball, roller, needle, and tapered roller. Continued
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All four styles convert sliding friction into rolling motion. All of the
weight of a vehicle or load on the bearing is transferred through the
rolling part. In a ball bearing, all of the load is concentrated into
small spots where the ball contacts the inner and outer race (rings).

Figure 73–2 Ball bearing point contact.

Continued
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Ball Bearings Hardened steel balls between the inner and outer
race to reduce friction in ball bearings . They cannot support the
same weight as roller bearings, however, there is less friction in
ball bearings and they generally operate at higher speeds.

Ball bearings can control thrust movement of an axle shaft

because the balls ride in grooves on the inner and outer races.
The groove walls resist lateral movement of the wheel on the
spindle. The most frequent use of ball bearings is at the rear
wheels of a rear-wheel-drive vehicle with a solid rear axle.

These bearings are installed into the axle housing and are often
press fitted to the axle shaft. Many front-wheel-drive vehicles use
sealed double-row ball bearings as a complete sealed unit and are
nonserviceable except as an assembly. See Figure 73–3.
Continued
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Figure 73–3 Radial load is the vehicle weight pressing on the wheels. The thrust load occurs as
the chassis components exert a side force during cornering.

Continued
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Roller Bearings Rollers between the inner and outer race to
reduce friction allow roller bearings a greater (longer) contact
area that can support heavier loads than a ball bearing.

Figure 73–4
Roller bearing line contact.

A needle bearing is a type of roller bearing that uses smaller rollers

called needle rollers. The clearance between the diameter of the
ball or straight roller is manufactured into the bearing to provide
the proper radial clearance and is not adjustable. Continued
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 Tapered Roller Bearings
The most commonly used
automotive bearing is the
tapered roller bearing.
By design, this bearing can
withstand radial loads (up
and down) as well as axial
loads (thrust) in one
direction.
Figure 73–5 A tapered roller bearing
will support a radial load and an
axial load in only one direction.

Not only is the bearing

itself tapered, but the
rollers are also tapered.
Continued
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Many non-drive-wheel bearings use tapered roller bearings. The
taper allows more weight to be handled by the bearings because
the weight is directed over the entire length of each roller rather
than concentrated on a small spot, as with ball bearings.

The rollers are held in place by a cage between the inner race
(called the inner ring or cone) and the outer race (also called the
outer ring or cup). Tapered roller bearings must be loose in the
cage to allow for heat expansion. Tapered roller bearings should
always be adjusted to allow for heat expansion.

On non-drive-axle vehicle wheels, the cup is tightly fitted to the

wheel hub and the cone is loosely fitted to the wheel spindle.
New bearings come packaged with the rollers, cage, and inner race
assembled together wrapped with moisture-resistant paper. See
Figure 73–6.
Continued
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Figure 73–6 Many tapered roller bearings use a plastic cage to retain the rollers.

Continued
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Inner and Outer Wheel Bearings Many rear-wheel-drive
vehicles use an inner and an outer wheel bearing on the front
wheels.

The inner wheel bearing is always the larger bearing because it is

designed to carry most of the vehicle weight and transmit the
weight to the suspension through to the spindle.

Between the inner wheel bearing and the spindle, there is a grease
seal, which prevents grease from getting onto the braking surface
and prevents dirt and moisture from entering the bearing.

See Figure 73–7.

Continued
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Figure 73–7 Non-drive-wheel hub with inner and outer tapered roller bearings. By angling the
inner and outer in opposite directions, axial (thrust) loads are supported in both directions.

INNER WHEEL BEARING

SPINDLE

OUTER WHEEL BEARING

Continued
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Standard Bearing Sizes Bearings use standard dimensions for
inside diameter, width, and outside diameter. The standardization
of bearing sizes helps interchangeability.

The dimensions that are standardized include bearing bore size

(inside diameter), bearing series (light to heavy usage), and
external dimensions. When replacing a wheel bearing, note the
original bearing brand name and number.

Replacement bearing catalogs usually have cross-over charts from

one brand to another. The bearing number is usually the same
because of the interchangeability and standardization within the
wheel bearing industry.

Continued
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Sealed Front-Wheel-Drive Bearings Most front-wheel-drive
(FWD) vehicles use a sealed nonadjustable front wheel bearing.

This type of bearing can include either two preloaded tapered roller
bearings or a double row ball bearing. This type of sealed bearing
is also used on the rear of many front-wheel-drive vehicles.

Double row ball bearings are often used because of their reduced
friction and greater seize resistance.

See Figures 73–8 and 73–9.

Continued
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Figure 73–8
Sealed bearing and hub assemblies are used on the front and rear wheels of many vehicles.

Continued
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Figure 73–9 Sealed bearing and hub assemblies are serviced as a complete unit as shown. This
assembly includes the wheel speed sensor.

Continued
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BEARING GREASES
Grease is an oil with a thickening agent to allow it to be installed
in places where a liquid lubricant would not stay. Greases are
named for their thickening agent, such as aluminum, barium,
calcium, lithium, or sodium
Grease Additives Commonly used additives in grease include:
Antioxidants
Antiwear agents
Rust inhibitors
Extreme pressure (EP) additives as sulfurized fatty oil or chlorine
Grease contains a dye to not only provide product identification
but to give a consistent color. A solid such as molybdenum
disulfide (moly), or graphite acts as an antiseize additive. Continued
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What Do Different Grease Colors Mean?
Nothing. According to grease manufacturers, grease is colored for
identification, marketing, and for consistency color reasons.
• Identification. The color is often used to distinguish one type of
grease from another within the same company. Blue grease from
one company may be totally different from the blue grease produced
or marketed by another company.
• Marketing. According to grease manufacturers, customers tend to
be attracted to a particular color of grease and associate that color
with quality.
• Consistency of color. All greases are produced in batches, and the
color of the finished product often varies in color from one batch to
another. By adding color to the grease, the color can be made
consistent.
Always use the grease recommended for the service being performed.

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Vehicle manufacturers specify the type and consistency of grease
for each application. The tech should know what the specs mean.

NLGI Classification The National Lubricating Grease Institute

(NLGI) uses the penetration test as a guide to assign the grease a
number. Low numbers are very fluid and higher numbers are more
firm or hard. See the chart below.

See the chart on

Page 871 of your
textbook.

Continued
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Grease is also classified according to quality. Wheel bearing
classifications include the following:
GA—mild duty
GB—moderate duty
GC—severe duty, high temperature
(frequent stop and go service)

GC indicates the highest quality. Chassis grease, used to lubricate

steering and suspension components, include the following:
LA—mild duty (frequent relubrication)
LB—high loads (infrequent relubrication)

LB indicates the highest quality. Most multipurpose greases are

labeled with both wheel bearing and chassis grease classifications
such as GC-LB.
Continued
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 More rolling bearings are destroyed by overlubrication than
underlubrication because heat generated in bearings cannot be
transferred easily to the air through the excessive grease.

Bearings should never be filled beyond one-third to one-half of their

grease capacity by volume

Smoking Can Kill You

Some greases contain polymers such as Teflon® that turn to a deadly gas
when burned. Always wash your hands thoroughly after handling grease
that contains these ingredients before smoking. If some of the grease is on
the cigarette paper and is burned, these polymers turn into nitrofluoric acid
—a deadly toxin.

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SEALS
Seals are used in all vehicles to keep lubricant, such as grease, from
leaking out and to prevent dirt, dust, or water from getting into the
bearing or lubricant. Two general applications of seals
are static and dynamic.

Static seals are used between two surfaces that do not move.

Dynamic seals are used to seal between two surfaces that move.

Wheel bearing seals are dynamic type seals that must seal between
rotating axle hubs and the stationary spindles or axle housing.

Continued
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Most dynamic seals use a synthetic rubber lip seal encased in metal.
The lip is often held in contact with the moving part with the aid of
a garter spring.

Figure 73–10 Figure 73–11 A garter spring helps hold the

Typical lip seal with a garter spring. sharp lip edge of the seal tight against the
shaft. (Courtesy of Dana Corporation)

Sealing lip should be installed toward the fluid being contained.

Continued
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 SYMPTOMS AND DIAGNOSIS OF DEFECTIVE
BEARINGS
Wheel bearings control the positioning and reduce the rolling
resistance of vehicle wheels. Whenever a bearing fails, the wheel
may not be kept in position and noise is usually heard.

With the vehicle off the ground, rotate the wheel by hand, listening
and feeling carefully for bearing roughness. Grasp the wheel at the
top and bottom and wiggle it back and forth, checking for bearing
looseness.

NOTE: Excessive looseness in the wheel bearings can cause a low brake
pedal. If any of the above symptoms are present, carefully clean and
inspect the bearings.

Continued
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Symptoms of defective wheel bearings include the following:
1. A hum, rumbling, or growling noise that increases with
vehicle speed
2. Roughness felt in the steering wheel that changes with the
vehicle speed or cornering
3. Looseness or excessive play in the steering wheel especially
while driving over rough road surfaces
4. A loud grinding noise in severe cases of a defective front
wheel bearing
5. Pulling during braking

Continued
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 “Bearing Overload”
It is not uncommon for vehicles to be overloaded. This is particularly
common with pickup trucks and vans. Whenever there is a heavy load, the
axle bearings must support the entire weight of the vehicle, including its
cargo. If a bump is hit while driving with a heavy load, the balls of a ball
bearing or the rollers of a roller bearing can make an indent in the race of
the bearing.
This dent or imprint is called brinelling, named after Johann A. Brinell, a
Swedish engineer who developed a process of testing for surface hardness
by pressing a hard ball with a standard force into a sample material to be
tested. Once this imprint is made, the bearing will make noise whenever
the roller or ball rolls over the indent.
Continued use causes wear to occur on all of the balls or rollers and
eventual failure. While this may take months to fail, the cause of the
bearing failure is often overloading of the vehicle. Avoid shock loads and
overloading for safety and for longer vehicle life.

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 Bearing Noise—Tire Noise
A defective wheel bearing is often difficult to diagnose because the noise is
similar to a noisy winter tire or a severely cupped tire. Customers often
request that tires be replaced as a result of the noise when the real
problem is a bad wheel bearing. To help determine if the noise is caused
by a wheel bearing or a tire, try these tips:
Tip 1—Drive the vehicle over a variety of road surfaces. If the noise
changes with a change in road surface, then the noise is caused
by a tire(s). If the noise remains the same, then the cause is a
defective wheel bearing.
Tip 2—Try temporarily overinflating the tires. If the noise changes,
then the tires are the cause. If the noise is the same, then
defective wheel bearings are the cause.

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 NON-DRIVE-WHEEL BEARING INSPECTION
AND SERVICE
The steps in a non-drive-wheel bearing inspection include:

1. Hoist the vehicle safely.

2. Remove the wheel.
3. Remove the brake caliper assembly and support it with a coat
hanger or other suitable hook to avoid allowing the caliper to
hang by the brake hose.
4. Remove the grease cap (dust cap).
5. Remove the old cotter key and discard.
NOTE: The term cotter, as in cotter key or cotter pin, is derived from the
Old English verb meaning “to close or fasten.”

Continued
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 Figure 73–12 Removing the grease cap
with grease cap pliers.

Figure 73–13 After wiggling the brake rotor

slightly, the washer and outer bearing can
be easily lifted out of the wheel hub.

Continued
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 6. Remove the spindle nut (castle nut).
7. Remove washer and outer wheel bearing.

Figure 73–14 Some techs remove the inner

wheel bearing and the grease seal at the
same time by jerking the rotor off the
spindle after reinstalling the spindle nut.
While this is a quick-and-easy method,
sometimes the bearing is damaged
(deformed) from being jerked out of the
hub using this procedure.

8. Remove the bearing hub from the spindle. The inner bearing
will remain in the hub and may be removed (simply lifted
out) after the grease seal is pried out.
Continued
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 9. Most vehicle and bearing manufacturers recommend
cleaning the bearing thoroughly in solvent or acetone.
If there is no acetone, clean the solvent off the bearings
with denatured alcohol to make certain that the thin
solvent layer is completely washed off and dry.
All solvent must be removed or allowed to dry from the
bearing because the new grease will not stick to a layer
of solvent.

NOTE: Some vehicle manufacturers do not recommend that “stringy-

type” wheel bearing grease be used. Centrifugal force can cause grease to
be thrown outward from the bearing. Because of the stringy texture, it may
not flow back into the bearing after it has been thrown outward. The final
result is a lack of lubrication and eventual bearing failure.

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10. Carefully inspect the bearings and the races for the following:

a. The outer race for lines, scratches, or pits.

See Figure 73–15.

b. The cage should be round. If the round cage has straight

sections, this is an indication of an over-tightened
adjustment or a dropped cage.

If either of the above is observed, the bearing, including

the outer race, must be replaced.

Failure to replace outer race (included when purchasing

a bearing) could lead to rapid failure of the new bearing.

See Figures 73–16 and 73–17.

Continued
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Figure 73–15 Wheel bearing inspection chart - Part 1

See the entire chart on Page 874 of your textbook. Continued

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Figure 73–15 Wheel bearing inspection chart - Part 2

See the entire chart on Page 874 of your textbook. Continued

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Figure 73–16 Figure 73–17
A wheel bearing race puller. Installing a bearing race with a driver.

Continued
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 11. Pack the cleaned or new bearing thoroughly with clean, new,
approved wheel bearing grease using hand packing or a
wheel- bearing packer. Clean out all of the old grease before
applying the recommended type of new grease.

Figure 73–18 When packing grease into

a cleaned bearing force grease around
each roller as shown.

Due to compatibility
problems, it is not
recommended that
greases be mixed.

Continued
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12. Place a thin layer of grease on the outer race.
13. Apply a thin layer of grease to the spindle, being sure to
cover the outer bearing seat, inner bearing seat, and shoulder
at the grease seal seat.
14. Install a new grease seal (also called a grease retainer) flush
with the hub using a seal driver.
15. Place approximately 3 tablespoons of grease into the grease
cavity of the wheel hub. Excessive grease could cause the
inner grease seal to fail, with the possibility of grease getting
on the brakes. Place the rotor with the inner bearing and seal
in place over the spindle until the grease seal rests on the
grease seal shoulder.
16. Install the outer bearing and the bearing washer.

Continued
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 17. Install the spindle nut and, while rotating the tire assembly,
tighten to about 12 to 30 lb. ft. with a wrench to “seat” the
bearing correctly in the race (cup) and on the spindle.

Figure 73–19
The wheel bearing adjustment procedure as specified for rear-wheel-drive vehicles.

Continued
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 18. While still rotating the tire assembly, loosen the nut
approximately one-half turn and then hand tighten only (about
5 lb. in.).
19. Install a new cotter key. (An old cotter key could break a part
off where it was bent and lodge in the bearing, causing major
damage.)
20. If the cotter key does not line up with the hole in the spindle,
loosen slightly (no more than 1/16 in. of a turn) until the hole
lines up. Never tighten more than hand tight.

NOTE: If the wheel bearing is properly adjusted, the wheel will still have
about 0.001 to 0.005 in. (0.03 to 0.13 mm) end play. This looseness is
necessary to allow the tapered roller bearing to expand when hot and not
bind or cause the wheel to lock up.

Continued
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 21. Bend the cotter key ends up and around the nut, not over the
end of the spindle where the end of the cotter key could rub
on the grease cap, causing noise.

Figure 73–20
A properly secured
wheel bearing adjust
nut.

Continued
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 22. Install the grease cap (dust cap) with a rubber mallet or soft-
faced hammer to help prevent denting or distorting the grease
cap. Install the wheel cover or hub cap.

Wheel Bearing Looseness Test

Looseness in a front wheel bearing can allow the rotor to move whenever
the front wheel hits a bump, forcing the caliper piston in, causing the brake
pedal to kick back and creates the feeling that the brakes were locking up.
Loose wheel bearings are easily diagnosed by removing the cover of
the master cylinder reservoir and watching the brake fluid as the front
wheels are turned left and right with the steering wheel. If the brake
fluid moves while the front wheels are being turned, caliper piston(s)
are moving in and out, caused by loose wheel bearing(s). If everything
is okay, the brake fluid should not move.

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CAUTION: Clean grease off the disc brake rotors or drums after
servicing the wheel bearings. Use a brake cleaner and a shop cloth. Even a
slight amount of grease on the friction surfaces of the brakes can harm the
friction lining and/or cause brake noise.

NOTE: Loose wheel bearings can also cause the brake pedal to sink due
to movement of the rotor, causing the caliper piston to move. This sinking
brake pedal is usually caused by a defective master cylinder. Before
replacing a master cylinder, check the wheel bearings.

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SEALED BEARING REPLACEMENT
Most front-wheel-drive vehicles use a sealed bearing assembly
bolted to the steering knuckle, supporting the drive axle or the rear,
as shown.

Figure 73–21
A rear wheel sealed
bearing hub assembly.

Continued
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Figure 73–22 Removing the drive axle shaft hub nut. This nut is usually very tight and the drift
(tapered) punch wedged into the cooling fins of the brake rotor keeps the hub from revolving
when the nut is loosened.

Many front-wheel-drive vehicles

use a bearing that must be
pressed off the steering knuckle.
Special aftermarket tools are
available to remove many of the
bearings without removing the
knuckle from the vehicle.
Check the factory service
manual and tool manufacturers
for exact procedures for the
vehicle being service.

Continued
See Figure 73–23.
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Figure 73–23 A special puller makes the job of removing the hub bearing from the knuckle easy
without damaging any component.

Continued
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Diagnosing a defective front bearing on a front-wheel-drive
vehicle is sometimes confusing.

A defective wheel bearing is usually noisy while driving straight,

and the noise increases with vehicle speed (wheel speed).

A drive axle shaft U-joint (CV joint) can also be the cause of noise
on a front-wheel-drive vehicle, but usually makes more noise
while turning and accelerating.

Continued
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REAR-DRIVE AXLE CLASSIFICATIONS
There are three rear-drive-axle classifications:
Full-floating
Three-quarter-floating
Semi-floating
These classifications indicate whether the axle shafts or the axle
housing supports the wheel.

The category of a rear drive axle is determined by how the wheel

and wheel bearing mount to the axle or housing.

Continued
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Full-Floating Axle The bearings are mounted and retained in the
hub of the brake drum or rotor. The hub and bearing mount onto the
axle housing, and are held in place by a bearing retainer or
adjustment nuts and safety locks.

The flanged end of the drive axle is attached to the hub by bolts or
nuts. The inner axle end splines into the differential side gears.
The wheel mounts onto the hub, and lug bolts or nuts retain it.

See Figure 73–24.

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Figure 73–24 A typical full-floating rear axle assembly.

The axle shafts “float” in the axle housing and drive the wheels
without supporting their weight. Because the axle shafts do not
retain the wheel, the axle shafts can usually be removed from the
vehicle while it is standing on the wheels.
Most three-quarter-ton pickups, all heavy-duty truck tractors, and
trailers use full- floating axles. Continued
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Three-Quarter-Floating Axle The bearings are mounted and retained in the brake drum or rotor
hub, which mounts onto the axle housing.

The outer extension of the hub fits onto the end of the axle, which is usually splined and tapered,
and a nut and cotter pin secure the hub to the axle. The axle shaft splines to the side gears inside the
differential.

The wheels are mounted on the hub and retained by lug bolts or nuts. As in the full-floating axle,
the axle housing and bearings in the hub support the weight in a three-quarter-floating axle.

Because of the construction of a three-quarter-floating axle, the wheel must be removed before
removing the axle shaft from the vehicle.

Continued
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Semi-Floating Axle The wheel bearings either press onto the axle
shaft or are installed in the outer end of the axle housing.

A retainer plate at the outer end of the axle shaft or a C-clip inside
the differential at the other end keeps the axle shaft in the housing.

The brake drum or rotor fits onto the end of the axle, and lug bolts
or nuts fasten the wheel to the drum or rotor and to the axle.

These axles are called “semi-floating” because only the inboard

ends of the axle shaft “float” in the housing.

The outboard end of the shaft retains the wheel and transmits the
weight of the wheel to the housing.

Continued
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Figure 73–25 Rear axle shafts may be full-floating, three-quarter-floating, or semi-floating,
depending on whether the shafts or the axle housing support the wheels.

Most solid-axle rear-wheel-drive cars and light trucks use a semi-floating

type of axle.

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 REAR AXLE BEARING AND SEAL
REPLACEMENT
Rear bearings on rear-wheel-drive vehicles are constructed and
serviced differently from other types of wheel bearings. Rear axle
bearings are either sealed or lubricated by the rear-end lubricant.

The rear axle must be removed from the vehicle to replace the rear
axle bearing. There are two basic types of axle retaining methods,
retainer plate-type and the C-lock.

NOTE: If the axle flange has an access hole, then a retainer plate-type
axle is used.

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Retainer Plate-Type Rear Axles Uses four fasteners that retain the
axle in the axle housing. To remove the axle shaft and the rear axle
bearing and seal, the retainer bolts or nuts must be removed.
The hole(s) in the wheel
flange permit a socket
wrench access to the
fasteners.
Figure 73–26 A retainer plate-type
rear axle bearing. Access to the
fasteners is through a hole in the
axle flange.

After fasteners have been

removed, the axle shaft
must be removed from the
rear axle housing.
Continued
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With the retainer plate-type rear axle, the bearing and the retaining
ring are press fit onto the axle and the bearing cup (outer race) is also
tightly fitted into the axle housing tube.

Figure 73–27
A slide hammer-type axle
puller can also be used.

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It is often necessary to remove the axle to perform a visual
inspection especially if trying to diagnose driveline noises.
Figure 73–28 The ball bearings fell out onto the ground when this axle was pulled out of the
axle housing. Diagnosing the cause of the noise and vibration was easy on this vehicle.

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NOTE: Some replacement bearings are available that are designed to ride
on a fresh, unworn section of the old axle. These bearings allow the use of
the original axle, saving the cost of a replacement axle.

The Brake Drum Slide Hammer Trick - Part 1

To remove the axle from a vehicle equipped with a retainer plate-type rear
axle, simply use the brake drum as a slide hammer to remove the axle from
the axle housing. If the brake drum does not provide enough force, a slide
hammer can also be used to remove the axle shaft.

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Figure 73–29 (a) To remove the axle from this vehicle equipped with a retainer-plate rear axle, the
brake drum was placed back onto the axle studs backward so that the drum itself can be used as
a slide hammer to pull the axle out of the axle housing. (b) A couple of pulls and the rear axle is
pulled out of the axle housing.

(a) (b)

Slide
Hammer
Trick -
Part 2

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C-Lock-Type Axles Vehicles that use C-locks (clips) use a straight
roller bearing supporting a semi-floating axle shaft inside the axle
housing.

The straight rollers do not have an inner race. The rollers ride on the
axle itself. If a bearing fails, both the axle and the bearing usually
need to be replaced.

The outer bearing race holding the rollers is pressed into the rear
axle housing. The axle bearing is usually lubricated by the rear-end
lubricant and a grease seal is located on the outside of the bearing.

The C-lock-type rear axle retaining method requires that the

differential cover plate be removed.

Continued
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Figure 73–30 To remove the C-lock (clip), Figure 73–31 The axle must be pushed inward
the lock bolt has to be moved before the slightly to allow the C-lock to be removed. After
pinion shaft. the C-lock has been removed, the axle can be
easily pulled out of the axle housing.

After cover removal, the differential pinion shaft is removed before

the C-lock that retains the axle can be removed. Continued
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NOTE: When removing the differential cover, rear axle lubricant will
flow from between the housing and the cover. Be sure to dispose of the old
rear axle lubricant in the environmentally approved way, and refill with the
proper type and viscosity (thickness) of rear-end lubricant. Check the
vehicle specifications for the recommended grade.

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Once the C-lock has been removed, the axle simply is pulled out
of the axle tube. Axle bearings with inner races are pressed onto
the axle shaft and must be pressed off using a hydraulic press

Figure 73–32 Using a hydraulic press

to press an axle bearing from the axle.
When pressing a new bearing back
onto the axle, pressure should only be
on the inner bearing race to prevent
damaging the bearing.

A bearing retaining collar

should be chiseled or
drilled into to expand the
collar, allowing it to be
removed.

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Figure 73–33 Removing an axle seal
using the axle shaft as the tool.

Follow the manufacturer’s

recommended bearing
removal and replacement
procedures.
Always replace the rear axle
seal whenever replacing a
rear axle bearing.
Check the differential vent.
A clogged vent can cause
excess pressure to build up
inside the differential and
cause rear axle seals to leak.

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BEARING FAILURE ANALYSIS
Whenever a bearing is replaced, the old bearing must be inspected
and the cause of the failure eliminated. See Figures 73–35 through
73–40 for examples of normal and abnormal bearing wear.
Figure 73–34 This is a normally worn bearing. If it does not have too much play, it can be reused.
(Courtesy SKF USA Inc.)

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Figure 73–35 (a) When corrosion etches into the surface of a roller or race, the bearing should
be discarded. (b) If light corrosion stains can be removed with an oil-soaked cloth, the bearing
can be reused. (Courtesy SKF USA Inc.)

(a)

Continued
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Figure 73–36 (a) When just the end of a roller is scored, it is because of excessive preload.
Discard the bearing. (b) This is a more advanced case of pitting. Under load, it will rapidly lead
to spalling. (Courtesy SKF USA Inc.)

(a)

Continued
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Figure 73–37 (a) Always check for faint grooves in the race. This bearing should not be reused.
(b) Grooves like this are often matched by grooves in the race (above). Discard the bearing.
(Courtesy SKF USA Inc.)

(a)

Continued
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Figure 73–38 (a) Regular patterns of etching in the race are from corrosion. This bearing should
be replaced. (b) Light pitting comes from contaminants being pressed into the race. Discard the
bearing. (Courtesy SKF USA Inc.)

(a)

Continued
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Figure 73–39 (a) This bearing is worn unevenly. Notice the stripes. It should not be reused.
(b) Any damage that causes low spots in the metal renders the bearing useless.
(Courtesy SKF USA Inc.)

(a)

Continued
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Figure 73–40 (a) In this more advanced case of pitting, you can see how the race has been
damaged. (b) Discoloration is a result of overheating. Even a lightly burned bearing should be
replaced. (Courtesy SKF USA Inc.)

(a)

Continued
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Figure 73–41 (a) Pitting eventually leads to spalling, a condition where the metal falls away in
large chunks. (b) In this spalled roller, the metal has actually begun to flake away from the
surface. (Courtesy SKF USA Inc.)

(a)
Metal Fatigue Long vehicle
usage, even under normal
driving conditions, causes
metal to fatigue & crack.
(b)

The metal between the

cracks can break out into
small chips, slabs, or scales
of metal, called spalling.

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Shock Loading Dents can be formed in the race of a bearing,
which eventually leads to bearing failure.

Figure 73–42
These dents resulted from the
rollers “hammering” against the
race, a condition called brinelling.
(Courtesy SKF USA Inc.)

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 What’s That Sound?
Defective wheel bearings usually make noise. The noise most defective wheel
bearings make sounds like noisy off-road or aggressive tread, or mud and snow tires.

Wheel bearing noise will remain constant while driving over different types of road
surfaces while tire tread noise usually changes with different road surfaces.

In fact, many defective bearings have been ignored by the vehicle owners and
technicians because it was thought that the source of the noise was the aggressive
tread design of the mud and snow tires. Always suspect defective wheel bearings
whenever you hear what seems to be extreme or unusually loud tire noise.

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PHOTO SEQUENCE Rear Axle Bearing

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PHOTO SEQUENCE Rear Axle Bearing (cont.)

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SUMMARY
1. Wheel bearings support the entire weight of a vehicle and are used to
reduce rolling friction. Ball and straight roller-type bearings are
nonadjustable while tapered roller-type bearings must be adjusted
for proper clearance.

2. Most front-wheel-drive vehicles use sealed bearings, either two

preloaded tapered roller bearings or double row ball bearings.

3. Most wheel bearings are standardized sizes.

Continued
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2009Pearson
PearsonEducation,
Education,Inc.
Inc.
By James D. Halderman Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458
SUMMARY (cont.)
4. A defective bearing can be caused by metal fatigue that leads to
spalling, shock loads that cause brinelling, or damage from
electrical arcing due to poor body ground wires or improper
electrical welding on the vehicle.

5. Bearing grease is an oil with a thickener. The higher the NLGI

number of the grease, the thicker or harder the grease
consistency.

6. Tapered wheel bearings must be adjusted by hand tightening the

spindle nut after properly seating the bearings. A new cotter key
must always be used.

Continued
Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition ©©2008
2009Pearson
PearsonEducation,
Education,Inc.
Inc.
By James D. Halderman Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458
SUMMARY (cont.)
7. Defective wheel bearings usually make more noise while
turning because more weight is applied to the bearing as the
vehicle turns.

8. All bearings must be serviced, replaced, and/or adjusted using

the vehicle manufacturer’s recommended procedures as stated
in the service manual.

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition ©©2008

2009Pearson
PearsonEducation,
Education,Inc.
Inc.
By James D. Halderman Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458
 end

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition ©©2008

2009Pearson
PearsonEducation,
Education,Inc.
Inc.
By James D. Halderman Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458