© 2012 delmar, cengage learning bearings, seals, and greases chapter 60

© 2012 Delmar, Cengage Learning

Bearings, Seals, and Greases

Chapter 60


Objectives• Understand terms that relate to wheel bearings• Select the correct grease to use for a particular

application• Describe the various wheel and axle bearing

arrangements• Service wheel bearings on front and rear axles


Introduction• Automobiles contain many types of bearings

– This chapter deals with fundamentals of bearings, seals, and lubricants

– Last part of chapter covers bearing service


Plain Bearings• Example: engine crankshaft bearings

– Do not use rolling parts

– Provide sliding contact between two mating surfaces

– Also called friction bearings


Frictionless Bearings• Provide a rolling contact

– Ball, roller, or needle bearings• Made of hardened steel alloys• Ground to a precise finish and size• Must be lubricated• Some are sealed

• Ball or roller bearings– Balls or rollers ride between an inner race and an

outer race

– Bearing cage holds balls or rollers in position


Bearing Loads• Bearings are made to handle different loads

– Radial load: bearing load in up-and-down direction

– Thrust load: load in front-to-rear direction • Also called axial thrust


Ball Bearings• Ride in machined grooves

– At rest: load is distributed equally wherever balls and races are in contact

• Control end thrust and radial movement– Must control thrust: groove in bearing race will be

offset to one side

• Single-row bearings – Susceptible to damage when shaft is misaligned


Roller Bearings• Used great load-carrying capacity is needed

– Provide more surface area of contact with the race

– Several types

– Do not control end thrust

• Most popular is the tapered roller bearing– Used for front-wheel bearings

– Can control end thrust when installed with tapers facing in opposite directions

• Needle bearing – Very small roller bearing


Wheel Bearings• Found on all wheels of a vehicle

– Axle bearings are on live axles

• Drive axle bearings – Located at ends of rear axle housing on RWD

car or on hub on FWD car

• Full-floating axles – Found on ¾ ton and larger trucks and vans

• FWD bearings – Compact and need to fit in a tight space


Greases• Greases are used in:

– Wheel bearings and chassis joints

– Universal joints and gear boxes

• Properties and characteristics of grease – Limited by quality of oil it is made of

– Greases are fibrous• Different sizes of fibers available

– Greases do not have a sharp melting point

– Viscosity of oil used in making grease is important to grease's apparent viscosity


Greases (cont'd.)• Automotive grease

– Classified by NLGI

• Grease types– Extreme pressure lubricants

• Same as those found in gear lubricants

– Chassis grease• Consistency allows application through zerk fitting

– Wheel bearing grease• Resistant to heat


Greases (cont'd.)– Universal joint grease

• Made for universal joints

– Multipurpose grease• Satisfies requirements of chassis, wheel bearing,

and universal joint lubricants

– Solid lubricant grease• Often used to lubricate speedometer cables,

emergency brake cables, splines, and leaf springs


Wheel Bearing Seals• Automobiles and

equipment use seals to:– Seal in lubricants

– Keep different lubricants separated

– Keep out dirt

– Maintain vacuum or pressure


Seal Materials and Design• Most popular seals are made of synthetic

materials– Most lip seals made of nitrile

• Silicone seals – Often used in engines and transmissions

• Fluoroelastomers – Used with special lubricants and chemicals

• Non-synthetic seals– Leather, felt, etc.


Seal Tolerance• Seals can accommodate shaft that is

undersized up to 1/64” if parts are in perfect alignment– RMA recommends runout tolerance be held to

±0.003” for shafts up to four inches in diameter

• Surface finish should be smooth


Wheel Bearing Diagnosis and Service

• Seal and bearing failure– Lubricant can leak out

• Moisture can leak in

• Boat trailer bearing failures– Common wheel bearing problem: trailer is towed

for a long distance before launching• Possible solution: Bearing Buddy®


Wheel Bearing Adjustment• Wheel bearings must be adjusted correctly

– Designed to operate with very little clearance

– Generic method of adjusting a loose bearing can be done with tire raised off ground

• Spindle nuts are kept in place with a cotter pin– Remove to tighten

– Washer under spindle nut has a tab that fits into spindle groove

• Prevents bearing from loosening or tightening

• Wheel bearing nuts are typically hexagonal


Wheel Bearing Adjustment (cont’d.)

• Selecting and installing a cotter pin– Use largest diameter

cotter pin that will fit into hole

– Pull longer end of cotter pin to seat fully in its hole

– Cut it off

– Cut off remaining end flush with spindle


Disc Brake Caliper Removal• Procedure for repacking disc brake wheel

bearings– Same as that followed for drum brakes

• Except disc caliper must be removed in order to gain access to the inside wheel bearing

• Caliper must be supported or wired to the steering knuckle support


Repacking Wheel Bearings• Major steps and considerations

– Remove hub and bearings from spindle• Seals are replaced during a bearing repack

– Use a long dowel or drift to remove the seal

– Clean out the old bearing

– Look for metal flakes

– Let the clean bearing air dry


Bearing Inspection and Diagnosis

• After cleaning inspect for damage– Spalling: pieces break off the bearing metal

– Brinelling: bearing or race has indentations

• Add grease to bearing– Pack with new grease by hand or pressure

bearing packer

– Put small amount of grease in cavity of hub

• Inspect the spindle– Clean and lubricate


Diagnosing Wheel Bearing Noise

• Driving car can help pinpoint problem– Check tires and bearings

– Make slow left and right turns• Shifts weight of vehicle from one side to the other• Weight increases on bearing: noise increases


Replacing Bearing Races• Anti-friction bearings usually have one race that

is pressed fit and the other is push fit– When a damaged wheel bearing is replaced:

pressed-fit race must be removed

– Old bearing race: removed by pounding it with a drift punch or special tool

– New race must fit the hub tightly

– New race can be chilled in refrigerator to make easier to install


Servicing Front-Wheel-Drive Bearings

• Most bearings on FWD vehicles are sealed– Require no service

• Remove axle to get to bearing– Puller often required

• Front-wheel bearing – Pressed or bolted onto the steering knuckle

• Some manufacturers recommend bearing replacement any time FWD assembly is removed– Special care required during reassembly

© 2012 delmar, cengage learning bearings, seals, and greases chapter 60

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