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Chapter 22
Driveshaft Assemblies
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Objectives (1 of 3)
Identify the components in a truck driveline.
Explain the procedures for inspecting,
lubricating, and replacing a universal joint.
Describe the various types of wear a
universal joint might experience.
Outline the procedure for sourcing chassis
vibration.
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Objectives (2 of 3)
Define and explain the importance of
phasing.
Explain the importance of driveline working
angles and how to calculate them.
Troubleshoot some typical driveline
complaints.
Describe the procedure for balancing adriveshaft.
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Objectives (3 of 3)
Describe the operation of a hydraulic
retarder.
Explain how an electric retarder operates.
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A Typical Truck Driveshaft
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Slip Joint
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Universal Joint
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A Stand Pipe
Ensures constant lubrication and prevents
dry startup.
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Bearing Cup with Needle Bearings
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Carrier Bearing
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Shop Talk
When replacing a hanger bearing, make sure
you look for and do not lose track of the shim
pack that is usually located between the
bearing mount and cross member. The shims set the driveshaft angles and
omitting them will result in a driveline
vibration.
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Parallel Arrangement
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Broken Back Arrangement
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Driveline Phasing
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Shop Talk
Clean grease fittings thoroughly to remove
accumulated grease and abrasives before
use.
Any contaminants on the zerk nozzle can beforced through the nipple into the bearing
during lubing.
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U-Joint Lube Schedule
See Table 222 on page 650 of the
textbook.
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Shop Talk
On-highway operation is generally defined as
an application that operates the vehicle
running less than 10 percent of total
operating time on gravel, dirt, or unimprovedroads.
Vehicles running more than 10 percent
operating time on poor road surfaces areclassified as off-highway in terms of
preventive maintenance.
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Warning
If grease is only seen to exit from three of the
four trunnion seals, the bearing is not
properly lubed and will almost certainly fail.
You must take the appropriate correctiveaction when U-joints fail to take grease.
If a driveshaft separates because of a U-joint
failure, it can take out air tanks, fuel tanks,and generally cause damage that greatly
exceeds the cost of replacing a single U-joint.
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How to Ensure Complete
Lubrication of the Slip Joint
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Caution
Half-round end yoke self-locking retaining
bolts should not be reused more than five
times.
If in doubt as to how many times bolts havebeen removed, replace with new bolts.
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Caution
When removing a driveshaft with half-round
or flange-type yokes, support the weight of
the driveshaft with a sling before separating
the U-joints.
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Caution
In cold temperatures, you should drive thevehicle immediately after lubricatingdriveshafts.
This activates the slip spline assembly andremoves excessive lubricant.
Excess lubricant in slip splines can freeze incold weather to a wax consistency and force
the breather plug out. This would expose theslip joint to contaminants and eventually resultin wear and seizure.
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Shop Talk
Before removing a driveshaft, mark the slip
yoke assembly and tube shaft with a paint
stick to ensure the correct phasing alignment
on reassembly. If the shaft assembly is to be cleaned before
reassembly, use a steel scribe to indent
alignment marks.
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Shop Talk
If only one end of the driveshaft requires service,
disconnect that end, unscrew the slip shaft seal
(dust cap) from the slip yoke assembly, and then
separate the driveshaft at the slip joint.
When removing the entire driveshaft, disassemble
one end at a time, laying the disconnected end on
the floor carefully.
When reassembling, be sure that the arrows ormarks on the shaft and slip joint are in line to keep
the driveshaft yokes in phase.
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Removing a U-Joint (1 of 2)
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Removing a U-Joint (2 of 2)
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Caution
If the bearing cap binds in the yoke bore,
gently tap with a ball peen hammer in the
center of the bearing cap.
Do not tap the outer edges of the bearing capbecause this could damage either the
bearing cup or the yoke.
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Caution
Once in use, bearing caps and their trunnions
should remain matched.
Also, never take assembly shortcuts by
installing only the new bearing caps on aused trunnion, as this will usually result in a
rapid failure.
Regard a U-joint cross, its four bearingassemblies, and mounting hardware as a unit
and replace as such.
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Caution
It makes sense to remove the grease fittings
when installing a driveshaft.
If they are knocked against the yoke, they tend
to shear. You can easily reinstall them afterthe driveshaft has been installed.
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Chassis Vibration Diagnosis Flowchart
See Table 223 on page 659 of the textbook.
C l l ti D i h ft
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Calculating Driveshaft
Operating Angles
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Checking Half-round Yoke Angles
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Driveshaft Troubleshooting Guide
See Table 224 on page 664 of the
textbook.
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Hydraulic Driveline Retarder
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Electric Retarder
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Summary (1 of 7)
The components of a driveshaft assembly includethe following:
Yoke
Universal joint
Slip spline
Hanger bearing
Propeller shaft(s)
The purpose of U-joints is to connect drivetraincomponents when allowing the driveshaft(s) to
operate at changing angles.
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Summary (2 of 7)
Two types of driveline arrangements areused to transmit torque to the drive axle
carriers: the parallel-joint type and the
nonparallel or broken-back driveshaft type. Because of U-joint action, when a drive yoke
turns at a constant rpm, the driveshaft speed
increases and decreases once per revolution.
This fluctuation in driveshaft speed requires
the U-joints to be in phase.
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Summary (3 of 7)
Driveline vibrations are caused by looseyokes, excessive driveshaft radial runout, slip
spline joint radial play, bent driveshaft tubing,
and failing U-joints. A U-joint puller should be used to separate a
universal joint from a yoke assembly.
Avoid using high impact tools such as sledgehammers, because driveshaft damage can
result.
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Summary (4 of 7)
After removing the U-joint cross and bearingcups from a yoke, inspect the yoke bores for
bore alignment, damage, and metal burrs.
Burrs can be removed with a rat tail or halfround file and emery cloth.
Measure the yoke bores for wear using a go-
no-go wear gauge and check yoke bore
alignment using a machined alignment bar.
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Summary (5 of 7)
When diagnosing driveline vibrations, itshould be noted that they often originate
elsewhere in the chassis.
An electronic inclinometer is the preferredinstrument for measuring driveline
component angles. A protractor also may be
used.
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Summary (7 of 7)
Electric driveline retarders operate byabsorbing the energy of motion by converting
it first to electrical energy using an eddy
current principle, and then dissipating it asheat.
Both hydraulic and electric driveline retarder
operation can be electronically controlled.