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Engine Speed Limiter
All engines have electronic engine speed limiting.
The engine limited speeds range between
2,900 and 4,400 rpm depending on engine option
content.
Engine Road Speed Governor
This system controls maximum vehicle speed
automatically and reduces engine power until vehicle
speed gets down to maximum governed speed.
The default setting for C4500 and C5500 models up to
19,500 lbs GVWR is 80 to 85 mph (128 to 136 km/h).
Most other models have a default setting of 75 mph
(120 km/h), although some tire sizes and tread
patterns may limit maximum speed to 55 to 65 mph
(86 to 105 km/h). You may have a label on the headliner
of your vehicle with more information on your engine
road speed governor. See your GM dealer for
assistance with programming your engine limited speed.
Safety Belt Reminders
Safety Belt Reminder Light
When the engine is started, a light will come on for
several seconds to remind people to fasten their
safety belts.
The safety belt light will
also come on and stay on
for several seconds.
Safety Belt Reminder Tone
If your vehicle has this feature, when the engine is
started, a tone will sound for several seconds to remind
people to fasten their safety belts.
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Page 199 of 384

If your vehicle has tow hooks, the hooks are at the front
and, on some models, the rear of the vehicle. You
may need to use them if you are stuck off-road and need
to be pulled to some place where you can continue
driving.Loading Your Vehicle
It is the responsibility of the Final Stage manufacturer to
install a Certification label on your vehicle. This label
shows how much weight your vehicle can properly carry.
It may also show the size of the vehicle’s original
tires, and the inflation pressures needed to obtain the
gross weight capacity of your vehicle. This is called the
Gross Vehicle Weight Rating (GVWR). The tire
information could also be shown on a separate Tire
Information label.
The GVWR includes the weight of the vehicle, all
occupants, fuel, and cargo.
The Certification label also tells you the maximum
weight for the front and rear axles, called the Gross Axle
Weight Rating (GAWR). To find out the actual loads
on your front and rear axles, go to a weigh station and
weigh your vehicle. Your dealer can help you with
this. Be sure to spread out your load equally on both
sides of the center line.
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Page 288 of 384

Dual Tire Operation
When the vehicle is new, check the wheel nut tightness
on all wheels with a torque wrench after your first
100 miles (160 km) and then 1,000 miles (1 600 km)
after that. Whenever a wheel, wheel bolt or wheel nut is
removed or serviced, repeat the 100 miles (160 km),
and then 1,000 mile (1 600 km) wheel nut tightness
check.
SeeTightening the Wheel Nuts on page 5-86for wheel
nut tightening information and proper torque values.
{CAUTION:
If you operate your vehicle with a tire that is
badly underin ated, the tire can overheat. An
overheated tire can lose air suddenly or catch
re. You or others could be injured. Be sure all
tires (including the spare, if any) are properly
in ated.
SeeTires on page 5-82andInflation - Tire Pressure on
page 5-82for more information on proper tire inflation.
When It Is Time for New Tires
Various factors, such as maintenance, temperatures,
driving speeds, vehicle loading, and road conditions,
influence when you need new tires.
Replace your tires when the tread depth is down to
1/8 of an inch (3.2 mm) for the front tires, or 1/16 of an
inch (1.6 mm) for a rear tire. Also, you need a new
tire if:
•You can see cord or fabric showing through the
tire’s rubber.
•The tread or sidewall is cracked, cut, or snagged
deep enough to show cord or fabric.
•The tire has a bump, bulge, or split.
•The tire has a puncture, cut, or other damage that
cannot be repaired well because of the size or
location of the damage.
The rubber in tires degrades over time, even if they are
not being used. This is also true for the spare tire, if
your vehicle has one. Multiple conditions affect how fast
this aging takes place, including temperatures, loading
conditions, and inflation pressure maintenance. With
proper care and maintenance tires will typically wear out
before they degrade due to age. If you are unsure about
the need to replace your tires as they get older, consult
the tire manufacturer for more information.
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If your vehicle has four-wheel drive, the axle differentials,
propshafts, and transfer case may be damaged if tires
of different sizes, brands or tread types are installed
on the front and rear axles. That damage would not be
covered under your warranty.
Buying New Tires
GM has developed and matched specific tires for your
vehicle. If you need replacement tires, GM strongly
recommends that you get tires that are the same size,
brand, load range, speed rating, and construction type
(radial and bias-belted tires) as your vehicle’s original
tires. This way, your vehicle will continue to have tires
that are designed to give the same performance and
vehicle safety, during normal use, as the original tires.
GM recommends replacing tires in sets of six or eight as
applicable. This is because uniform tread depth on all
tires will help keep your vehicle performing most like it
did when the tires were new. Replacing less than a full
set of tires can affect the braking and handling
performance of your vehicle.
{CAUTION:
Mixing tires could cause you to lose
control while driving. If you mix tires of
different sizes, brands, or types (radial
and bias-belted tires) the vehicle may not
handle properly, and you could have a
crash. Using tires of different sizes,
brands, or types may also cause damage
to your vehicle. Be sure to use the correct
size, brand, and type of tires on your
vehicle’s wheels.
{CAUTION:
If you use bias-ply tires on your vehicle,
the wheel rim anges could develop
cracks after many miles of driving. A tire
and/or wheel could fail suddenly, causing
a crash. Use only radial-ply tires with the
wheels on your vehicle.
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