chapter 24 bennet
TRANSCRIPT
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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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j g
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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y
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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y
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.