1. Bearings, Seals, and Greases
Chapter 60

2. 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

3. Introduction Automobiles contain many types of bearings
This chapter deals with fundamentals of bearings, seals, and lubricants
Last part of chapter covers bearing service

4. Plain Bearings Example: engine crankshaft bearings
Do not use rolling parts
Provide sliding contact between two mating surfaces
Also called friction bearings

5. 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

6. 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

7. 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

9. 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

11. Wheel Bearings Found on all wheels of a vehicle Drive axle bearings
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

12. Greases Greases are used in: Properties and characteristics of grease
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

13. Greases (cont'd.) Automotive grease Grease types Classified by NLGI
Extreme pressure lubricants
Same as those found in gear lubricants
Chassis grease
Consistency allows application through zerk fitting
Wheel bearing grease
Resistant to heat

14. Greases (cont'd.) Universal joint grease Multipurpose 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

15. Wheel Bearing Seals Automobiles and equipment use seals to:
Seal in lubricants
Keep different lubricants separated
Keep out dirt
Maintain vacuum or pressure

16. 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.

17. 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

18. 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®

19. 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

20. 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

21. 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

22. 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

23. 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

24. 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

25. 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

26. 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