34 Fleet Maintenance | October 2017
Balance is an important part of the
driveline because its components are
not in a straight line. Each driveshaft ’s
U-joints allow diff erent segments of the
driveline to operate in diff erent planes
or at diff erent angles to transfer torque
and rotation to the rear axles, explains
Meritor’s Iott. Th ese planes (or operating
angles) can change dynamically as a
suspension moves up and down during
vehicle operation. Specifi c design rules
must be followed during chassis design
to ensure the driveline angles work
together to cancel vibrations created
by the U-joint’s cardan U-joint design.
So, when balance issues occur there
can be excess vibration or squeaking
noises.
Warning signs for technicians of a
potential driveline failure are as follows:
Excessive movement in the U-joint
U-joint caps or straps fasteners are loose
Movement in the center bearing
mounting or bearing
Excessive movement in a slip yoke
spline
Fasteners that show signs of “fretting
corrosion” on the matting surfaces are
loose fasteners
U-joint journals that do not purge
grease
Slip yoke seal that has popped loose
of the slip yoke
Dents or bent driveline tube
Missing weld balance weights
Th ere are also warning signs for
drivers, which can signal potentional
driveline failure. (See “Warning Signs
for Drivers of Driveline Failure”).
Proper Maintenance
“Th e Benjamin Franklin axiom that, ‘an
ounce of prevention is worth a pound of
cure,’ can be applied to the driveline,”
» Use a bright light when inspecting driveline components
to find potential problems earlier.
Photo from iStock
Dana’s Bosler says. “Proper inspection
and maintenance can be the diff erence
between making deliveries on time and
having expensive repairs in the fi eld.”
VehicleServicePros.com/11669575
Warning Signs For Drivers Of Driveline Failure
Truck drivers are often the first to experience a difference
in the performance of a vehicle. In some cases, those warning
signs could signify a possible costly driveline failure.
Notify drivers of the following warning signs, provided by Meritor’s
Product Technical Specialist Eric Iott, and perhaps also prepare
an easy way for drivers to report these symptoms to the proper
authority so these issues do not go unreported.
Meritor, Inc. (www.meritor.com) is a global supplier of axle, brake and
suspension solutions to OE manufacturers and the aftermarket.
Consider the following warning signs drivers should be aware of on the road:
VIBRATION IN THE SEAT
“When drivers start to feel a vibration in their seats, it could be associated with
the driveline,” Iott explains. “Drivelines rotate at a different frequency than a
tire and that vibration will have a different sound and feel than tire hop. Drivers
can be secondary advisers of a pending driveline failure, but the pending failure
is more advanced by the time drivers feel it in the cab. Drivers should seek
immediate help and have a qualified technician look into the vibration.”
This vibration may also increase with driveline speed,
PACCAR Parts’ Product Director Pepe Ramos adds.
PACCAR Parts (www.paccarparts.com), a division of PACCAR,
Inc., is a global distributor of aftermarket parts for heavy and
medium duty trucks, trailers, buses and engines.
SUSPENSION RIDE HEIGHT ISSUE
“A lower-frequency ‘growling’ noise coming from the transmission could be
the sign of a suspension ride height issue,” Iott says. “Driveline cancellation
angles are affected when the air ride height on the tractor’s air ride suspension
is not maintained at correct height. Drivers may be the cause of this
vibration problem if re-inflating the tractor’s air suspension after detaching
from a trailer was overlooked. The driveline U-joints and slip yokes splines
will be damaged if the condition continues for a long period of time.”