operators_manual

• New springs settle-in after the
vehicle's initial service, causing the
U-bolts to become loose
Rear Suspension Fasteners
To maintain the performance of the air
suspension, check fastener torque values
after the first 2,000 miles (3,200 km) of
service and every 60,000 miles (96,000
km) thereafter. Torque recommendations
apply to fasteners supplied and installed by
vehicle manufacture. The values listed at
the back of this chapter (See Suspension
U-Bolts, Grade 8 on page 306 and Frame
Fastener Torque Requirements on page
304), are for cadmium plated or phosphate
and oil fasteners only.
Rear Suspension U-Bolts
U-bolts are difficult to tighten unless you
have the right equipment. If you cannot
tighten them correctly yourself, be sure to
have them checked and tightened regularly
by an authorized mechanic.
NOTE
To ensure an accurate torque reading,
use properly maintained and calibrated
torque wrenches. Clean the nut and
bolt. No dirt, grit, or rust should be
present.
WARNING
DO NOT operate the vehicle if the sus-
pension U-bolts are not properly tight-
ened. Loose U-bolts will cause the
axle to not be properly secured to the
suspension, which could cause loss of
vehicle control and an accident. Loose
U-bolts can also cause uneven tire
wear and poor alignment. Failure to
comply may result in death, personal
injury, equipment or property damage.
NOTE
Whenever possible, torque all frame
fasteners on the nut end, not the bolt
head.
Load the vehicle to its normal gross weight
before tightening U-bolts. Loading the
vehicle ensures proper adjustment of the
U-bolt and spring assembly.
WARNING
DO NOT replace U-bolts and nuts with
common U-bolts or standard nuts.
These parts are critical to vehicle safe-
ty. If the wrong U-bolts or nuts are
used, the axle could loosen or sepa-
rate from the vehicle and cause a seri-
ous accident. Use only U-bolts and
nuts of SAE Grade 8 specification or
better. Failure to comply may result in
death, personal injury, equipment or
property damage.
Rear Axle Lubrication
See the axle manufacturer's operator's
manual for lubrication specifications and
service intervals.
Check oil level with the vehicle parked on
level ground and the fluid warm. The level
should be even with the bottom of the filler
hole.
Rear Axle Alignment
Continual road shock and load stresses
may force the rear axles out of alignment.
If you detect rapid tire wear on the rear
MAINTENANCE - Rear Axle and Suspension
284 Y53-6126-1A1 (01/21)
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