2008 GMC ENVOY Owner's Manual

{CAUTION:
Shifting a four-wheel-drive vehicle’s transfer
case into NEUTRAL can cause your vehicle to
roll even if the transmission is in PARK (P).
You or others could be injured. Make sure the
parking brake is rmly set before you shift the
transfer case to NEUTRAL.
6. Shift the transfer case to NEUTRAL (N). See
Four-Wheel Drive on page 2-29for the proper
procedure to select the NEUTRAL (N) position for
your vehicle.
7. Release the parking brake only after the vehicle
being towed is rmly attached to the towing
vehicle.
8. Turn the ignition off.
After towing, see “Shifting Out of Neutral” under
Four-Wheel Drive on page 2-29.
Rear Towing (Rear Wheels Off
the Ground)
(Two-Wheel or Four-Wheel-Drive Vehicles)
Use the following procedure to tow your vehicle from
the rear:
1. Drive the vehicle onto the dolly.
2. Firmly set the parking brake. SeeParking Brake on
page 2-33for more information.
3. Shift the transmission in PARK (P).
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4. Follow the dolly manufacturer’s instructions to
attach and secure the vehicle being towed to
the dolly and then the loaded dolly to the tow
vehicle. Use an adequate clamping device to ensure
that the front wheels are locked into the straight
position.
5. Release the parking brake only after the vehicle
being towed is rmly attached to the towing
vehicle.
6. Turn the ignition to LOCK.
If the tow vehicle will not be started or driven for
six weeks or more, remove the battery cable
from the negative terminal (post) of the battery.
Electronically Controlled Air
Suspension System
Your vehicle may be equipped with an electronically
controlled air suspension system that automatically
keeps your vehicle level as you load and unload.
The system includes a compressor, two height
sensors and two air springs supporting the rear axle.The system also has an internal clock to prevent
overheating if the inator is used for prolonged periods.
If the system overheats, all leveling function stops
until the system cools down. During this time, the
indicator light on the air inator switch will be ashing.
The ignition has to be on for the system to inate,
in order to raise the vehicle to the standard ride height
after loading. The system can lower the vehicle to
the standard ride height after unloading with the ignition
on and also for up to 30 minutes after the ignition
has been turned off.
You may hear the compressor operating when you load
your vehicle, and periodically as the system adjusts
the vehicle to the standard ride height.
Load leveling will not function normally with the inator
hose attached to the inator outlet. Remove the inator
hose from the outlet during loading and unloading.
If the vehicle is parked for an extended period of time,
some bleed down of the suspension is normal. Upon
starting the vehicle, proper height will be achieved.
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Overload Protection
The air suspension system is equipped with overload
protection. Overload protection is designed to protect
the air suspension system, and it is an indicator to
the driver that the vehicle is overloaded. When
the overload protection mode is on, it will not allow
damage to the air compressor. However, do not
overload the vehicle. SeeLoading Your Vehicle
on page 4-34.
If the suspension remains at a low height, the rear
axle load has exceeded GAWR (Gross Axle Weight
Rating). When the overload protection mode is activated,
the compressor operates for about 30 seconds to one
minute without raising the vehicle depending on the
amount of overload. This will continue each time
the ignition is turned on until the rear axle load is
reduced below GAWR.
Indicator Light
The indicator light on the inator switch in the rear
passenger compartment also serves as an indicator for
internal system error. If the indicator light is ashing
without the load leveling function or the inator being
active, turn off the ignition. The next day turn on the
ignition and check the indicator light. The vehicle can
be driven with the light ashing, but if it is you should
have the vehicle serviced as soon as possible.
Towing a Trailer
{CAUTION:
If you do not use the correct equipment and
drive properly, you can lose control when you
pull a trailer. For example, if the trailer is too
heavy, the brakes may not work well — or even
at all. You and your passengers could be
seriously injured. You may also damage your
vehicle; the resulting repairs would not be
covered by your warranty. Pull a trailer only if
you have followed all the steps in this section.
Ask your dealer/retailer for advice and
information about towing a trailer with
your vehicle.
Notice:Pulling a trailer improperly can damage
your vehicle and result in costly repairs that would
not be covered by your warranty. Always follow
the instructions in this section and check with your
dealer/retailer for more information about towing
a trailer with your vehicle.
To identify the trailering capacity of your vehicle, you
should read the information in “Weight of the Trailer” that
appears later in this section.
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Trailering is different than just driving your vehicle by
itself. Trailering means changes in acceleration, braking,
handling, durability and fuel economy. Successful,
safe trailering takes correct equipment, and it has to
be used properly.
That’s the reason for this part. In it are many
time-tested, important trailering tips and safety rules.
Many of these are important for your safety and that of
your passengers. So please read this section carefully
before you pull a trailer.
If You Do Decide To Pull A Trailer
If you do, here are some important points:
There are many different laws, including speed limit
restrictions, having to do with trailering. Make sure
your rig will be legal, not only where you live but also
where you’ll be driving. A good source for this
information can be state or provincial police.
Consider using a sway control. See “Hitches” later in
this section.
Don’t tow a trailer at all during the rst 500 miles
(800 km) your new vehicle is driven. Your engine,
axle or other parts could be damaged.
Then, during the rst 500 miles (800 km) that you tow
a trailer, don’t drive over 50 mph (80 km/h) and don’t
make starts at full throttle. This helps your engine
and other parts of your vehicle wear in at the heavier
loads.
You can tow in DRIVE (D). You may want to shift the
transmission to THIRD (3) or, if necessary, a lower
gear selection if the transmission shifts too often
(e.g., under heavy loads and/or hilly conditions).
Three important considerations have to do with weight:
the weight of the trailer,
the weight of the trailer tongue
and the weight on your vehicle’s tires.
Weight of the Trailer
How heavy can a trailer safely be?
It depends on how you plan to use your rig. For example,
speed, altitude, road grades, outside temperature and
how much your vehicle is used to pull a trailer are all
important. It can also depend on any special equipment
that you have on your vehicle, and the amount of tongue
weight the vehicle can carry. See “Weight of the Trailer
Tongue” later in this section for more information.
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Maximum trailer weight is calculated assuming only the
driver is in the tow vehicle and it has all the required
trailering equipment. The weight of additional optional
equipment, passengers and cargo in the tow vehicle
must be subtracted from the maximum trailer weight.Look in the following chart to nd the maximum trailer
weight for your vehicle.
Vehicle Axle Ratio Max.Trailer Wt. *GCWR
2WD Envoy (4.2 L L6 Engine)3.42 5,300 lbs (2 404 kg) 10,000 lbs (4 536 kg)
3.73 5,800 lbs (2 631 kg) 10,500 lbs (4 763 kg)
4.10 6,300 lbs (2 858 kg) 11,000 lbs (4 990 kg)
2WD Envoy (5.3 L V8 Engine)3.42 6,100 lbs (2 767 kg) 11,000 lbs (4 990 kg)
3.73 6,600 lbs (2 994 kg) 11,500 lbs (5 216 kg)
4WD Envoy (4.2 L L6 Engine)3.42 5,200 lbs (2 359 kg) 10,000 lbs (4 536 kg)
3.73 5,700 lbs (2 858 kg) 10,500 lbs (4 763 kg)
4.10 6,200 lbs (2 812 kg) 11,000 lbs (4 990 kg)
4WD Envoy (5.3 L V8 Engine)3.42 6,000 lbs (2 721 kg) 11,000 lbs (4 990 kg)
3.73 6,500 lbs (2 948 kg) 11,500 lbs (5 216 kg)
*The Gross Combination Weight Rating (GCWR) is the total allowable weight of the completely loaded vehicle and
trailer including any passengers, cargo, equipment and conversion. The GCWR for your vehicle should not be
exceeded.
Ask your dealer for our trailering information or advice,
or write us at our Customer Assistance Offices. See
Customer Assistance Offices on page 7-6for more
information.
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Weight of the Trailer Tongue
The tongue load (A) of any trailer is an important weight
to measure because it affects the total or gross weight of
your vehicle. The Gross Vehicle Weight (GVW) includes
the curb weight of the vehicle, any cargo you may carry in
it, and the people who will be riding in the vehicle. If you
have a lot of options, equipment, passengers or cargo in
your vehicle, it will reduce the tongue weight your vehicle
can carry, which will also reduce the trailer weight your
vehicle can tow. And if you will tow a trailer, you must add
the tongue load to the GVW because your vehicle will be
carrying that weight, too. See Loading Your Vehicle for
more information about your vehicle’s maximum load
capacity.
The trailer tongue weight (A) should be 10 percent to
15 percent of the total loaded trailer weight (B), up to a
maximum of 400 lbs (181 kg) with a weight carrying hitch.The trailer tongue weight (A) should be 10 percent to
15 percent of the total loaded trailer weight (A), up to a
maximum of 900 lbs (408 kg) for a weight distributing
hitch.
Do not exceed the maximum allowable tongue weight
for your vehicle. Choose the shortest hitch extension
that will position the hitch ball closest to the vehicle.
This will help reduce the effect of trailer tongue weight
on the rear axle.
After you’ve loaded your trailer, weigh the trailer and
then the tongue, separately, to see if the weights
are proper. If they aren’t, you may be able to get
them right simply by moving some items around
in the trailer.
Trailering may be limited by the vehicle’s ability to carry
tongue weight. Tongue weight cannot cause the vehicle
to exceed the GVWR (Gross Vehicle Weight Rating) or
the RGAWR (Rear Gross Axle Weight Rating). The effect
of additional weight may reduce your trailering capacity
more than the total of the additional weight.
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Consider the following example:
A vehicle model base weight is 5,500 lbs (2 495 kg);
2,800 lbs (1 270 kg) at the front axle and 2,700 lbs
(1 225 kg) at the rear axle. It has a GVWR of 7,200 lbs
(3 266 kg), a RGAWR of 4,000 lbs (1 814 kg) and
a GCWR (Gross Combination Weight Rating) of
14,000 lbs (6 350 kg). The trailer rating should be:
You can expect tongue weight to be at least 10 percent
of trailer weight (850 lbs (386 kg)) and because the
weight is applied well behind the rear axle, the effect on
the rear axle will be greater than just the weight itself, as
much as 1.5 times as much. The weight at the rear axle
could be 850 lbs (386 kg) X 1.5 = 1,275 lbs (578 kg).
Since the rear axle already weighs 2,700 lbs (1 225 kg),
adding 1,275 lbs (578 kg) brings the total to 3,975 lbs
(1 803 kg). This is very close to, but within the limit for
RGAWR as well. The vehicle is set to trailer up to
8,500 lbs (3 856 kg).But let’s say your specic vehicle is equipped with some
of the latest options and you have a front seat passenger
and two rear seat passengers with some luggage and
gear in the vehicle as well. You may add 300 lbs (136 kg)
to the front axle weight and 400 lbs (181 kg) to the rear
axle weight. Your vehicle now weighs:
Weight is still below 7,200 lbs (3 266 kg) and you may
think that you should subtract 700 additional pounds
(318 kg) from your trailering capacity to stay within
GCWR limits. Your maximum trailer would only be
7,800 lbs (3 538 kg). You may go further and think you
must limit tongue weight to less than 1,000 lbs (454 kg)
to avoid exceeding GVWR. But, you must still consider
the effect on the rear axle. Because your rear axle now
weighs 3,100 lbs (1 406 kg), you can only put 900 lbs
(408 kg) on the rear axle without exceeding RGAWR.
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The effect of tongue weight is about 1.5 times the actual
weight. Dividing the 900 lbs (408 kg) by 1.5 leaves you
with being able to handle only 600 lbs (272 kg) of tongue
weight. Since tongue weight is usually at least 10 percent
of total loaded trailer weight, you can expect that the
largest trailer your vehicle can properly handle is
6,000 lbs (2 721 kg).
It is important that you make sure your vehicle does not
exceed any of its ratings — GCWR, GVWR, RGAWR,
Maximum Trailer Rating or Tongue Weight. The
only way to be sure you are not exceeding any of
these ratings is to weigh your vehicle and trailer.Total Weight on Your Vehicle’s Tires
Be sure your vehicle’s tires are inated to the upper
limit for cold tires. You’ll nd these numbers on
the Certication label at the rear edge of the driver’s
door or see Loading Your Vehicle for more information.
Then, be sure you don’t go over the GVW limit for
your vehicle, or the GAWR, including the weight of the
trailer tongue. If you use a weight distributing hitch,
make sure you don’t go over the rear axle limit before
you apply the weight distribution spring bars.
Hitches
It’s important to have the correct hitch equipment.
Crosswinds, large trucks going by and rough roads
are a few reasons why you’ll need the right hitch.
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