Chapter 24 Bennet

7/29/2019 Chapter 24 Bennet

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Chapter 24

Heavy-Duty Truck

Axle Service and Repair


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Objectives (1 of 2)

Describe the lubrication requirements of truck

and trailer dead axles.

Outline the lubrication service procedures

required for truck drive axle assemblies.

Perform some basic level troubleshooting on

differential carrier gearing.

Outline the procedure required todisassemble a differential carrier.


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Objectives (2 of 2)

Disassemble a power divider unit.

Perform failure analysis on power divider and

differential carrier components.

Reassemble power divider and differential

carrier assemblies.


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Axle Fill and Drain Plugs


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Axle Lube Viscosity

See Table 24-1 on page 706 in the textbook.


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Shop Talk

Draining lubricants when warm ensures that

contaminants are still suspended and also

reduces drain time.


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Power Divider

Oil Fill and Drain Plugs


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Checking the Lube Level


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Proper Lubricant Levels


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Caution

On most drive axles, there is no external

visual means of checking lubricant level in

the wheel end, so the importance of making

sure the drive axle lubricant level is correctcannot be overemphasized.

Raising each side of an axle with a jack

ensures oil fills the wheel-end hub cavity. Make a final check of the differential carrier

oil level after tilting the axle from both sides.


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Wheel Hub Lube Cavity


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Differential Carrier Identification


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Axle Identification


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Crown Gear and Pinion Identification


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Failure Analysis

Shock load

Fatigue

Spinout

Faulty lubrication

Normal wear


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Caution

Most driver-abuse generated failures do not

cause an instantaneous equipment failure.

The equipment failure can take place some

time after the driving incident that generatedit.

This is important to remember when

attempting to attribute blame in fleets that donot assign drivers dedicated trucks.


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Fracture Patterns


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Surface Failure Patterns


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Torsional Failure


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Bending Failure Patterns


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Spinout

Al S t


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Always Support

the Truck With Axle Stands


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Shop Talk

You sometimes have to use more force to

pop axle shafts than can be delivered using a

drift and 4-lb. hammer.

When this method does not work, use a 16-lb. sledgehammer directly on center of the

axle shaft flange; use a swing of the

sledgehammer, letting the weight of thehammer do all of the work.


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Caution

Most of the weight of a differential carrier

assembly is on the inboard side of its

mounting flange.

Ensure that the assembly is properlyfastened to the jacking device and that your

body is never positioned under the carrier.


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Thrust Screw


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Marking the Carrier Components


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Lock Plate and Adjusting Rings

Removing the


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Removing the

Bearing Cap and Adjusting Ring


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Differential Spider Gears


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Drill and Punch Out Rivets


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Caution

Do not remove the rivet heads or rivets with a

chisel and hammer because this can damage

the flange case half or enlarge the rivet

holes, resulting in loose rivets.


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Remove the Ring Gear

Removing the


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Removing the

Pinion Flange or Yoke


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Bearing Cage Removal

Removing Pinion


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Removing Pinion

with Bearing Cage

Pressing the Drive


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Pressing the Drive

Pinion from the Bearing Cage

Pi i B i R l


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Pinion Bearing Removal

S i t B i


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Spigot Bearing

R i P Di id


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Removing Power Divider

P Di id D l Pi


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Power Divider Dowel Pins

P Di id A bl


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Power Divider Assembly

I t l Diff ti l


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Interaxle Differential

Measuring End Play


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Measuring End Play

Pinion Bearing Cage Assembly


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Pinion Bearing Cage Assembly

Check Pinion Bearing Preload


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Check Pinion Bearing Preload

A Tool to Check Rolling Resistance


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A Tool to Check Rolling Resistance

Checking Rolling Resistance


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Checking Rolling Resistance

Drive Pinion Depth Controlled


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Drive Pinion Depth Controlled

by Shim Pack Thickness

Pinion Cone Variation Number


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Pinion Cone Variation Number

Determining Shim Pack Thickness


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Determining Shim Pack Thickness

See Figure 24-59 on page 732 of thetextbook.

Checking Crown Gear Runout


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Checking Crown Gear Runout

Check Crown Gear Backlash


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Check Crown Gear Backlash

Adjustments to Increase Backlash


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Adjustments to Increase Backlash

Adjustments to Decrease Backlash


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Adjustments to Decrease Backlash

Crown Gear Tooth Nomenclature


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Crown Gear Tooth Nomenclature

Checking Tooth Contact


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Checking Tooth Contact

Correct Contact


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Pattern for Used Gearing

Incorrect Pinion Position


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Incorrect Backlash Patterns


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Adjusting the Thrust Screw


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Summary (1 of 6)


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y ( )

Adhering to OEM-recommended lubricationschedules is the key to ensuring the longest

service life from both drive and dead axles.

Knowing the correct procedure to checklubricant level is essential.

The level is correct when lubricant is exactly

level with the bottom of the fill hole.

Summary (2 of 6)


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Because most OEMs approve of the use ofsynthetic lubricants in final drive carriers, lubrication

drain schedules have been greatly increased in

recent years.

Drain schedules are determined by the actuallubricant used and the type of application to which the

vehicle is subjected.

Servicing of axles on heavy-duty trucks consists of

routine inspection, lubrication, cleaning, and, whenrequired, troubleshooting and component overhaul.

Summary (3 of 6)


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Failure analysis is required to preventrecurrent failures.

Drive axle carrier components usually fail for

one of the following reasons: Shock load

Fatigue

Spinout Lubrication problems

Normal wear

Summary (4 of 6)


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Most differential carriers are replaced asrebuilt/exchange units, so the role of the

technician is, more often than not, to

diagnose the problem and then, if necessary,replace the defective assembly as a unit.

The technician who has disassembled and

reassembled differential carriers should find

troubleshooting procedures easier to follow.

Summary (5 of 6)


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Follow the OEM procedure whendisassembling differential carriers.

Taking a few moments to measure shim packsand gear tooth contact patterns on

disassembly can save considerable time whenreassembling the carrier.

A crown and pinion gearset often can bereused when rebuilding a differential carrier.Make sure you inspect it properly ondisassembly.

Summary (6 of 6)


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Crown and pinion gearsets are alwaysreplaced as a matched pair during a rebuild.

When setting crown and pinion backlash, it is

increased by moving the crown gear awayfrom the drive pinion, and decreased by

moving the crown gear toward the drive

pinion.

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