2008 CHEVROLET SUBURBAN Rear axle

{CAUTION:
Do not load the vehicle any heavier than
the Gross Vehicle Weight Rating (GVWR),
or either the maximum front or rear Gross
Axle Weight Rating (GAWR). If you do,
parts on the vehicle can break, and it can
change the way your vehicle handles.
These could cause you to lose control
and crash. Also, overloading can shorten
the life of the vehicle.
Notice:Overloading your vehicle may cause
damage. Repairs would not be covered by your
warranty. Do not overload your vehicle.The label will help you decide how much cargo
and installed equipment your truck can carry.
Using heavier suspension components to
get added durability might not change your weight
ratings. Ask your dealer to help you load your
vehicle the right way.
If you put things inside your vehicle — like
suitcases, tools, packages, or anything
else — they go as fast as the vehicle goes. If you
have to stop or turn quickly, or if there is a
crash, they will keep going.
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{CAUTION:
Things you put inside your vehicle can
strike and injure people in a sudden stop
or turn, or in a crash.
Put things in the cargo area of your
vehicle. Try to spread the weight
evenly.
Never stack heavier things, like
suitcases, inside the vehicle so that
some of them are above the tops of
the seats.
Do not leave an unsecured child
restraint in your vehicle.
When you carry something inside the
vehicle, secure it whenever you can.
Do not leave a seat folded down
unless you need to.
There is also important loading information for
off-road driving in this manual. See “Loading Your
Vehicle for Off-Road Driving” underOff-Road
Driving on page 4-13.
Adding a Snow Plow or Similar
Equipment
Before installing a snow plow on your vehicle, here are
some things you will need to know:
Notice:If your vehicle does not have the snow
plow prep package, adding a plow can damage your
vehicle, and the repairs would not be covered by
warranty. Unless your vehicle was built to carry
a snow plow, do not add one to your vehicle. If your
vehicle has the snow plow prep package, called
RPO VYU, then the payload your vehicle can carry
will be reduced when a snow plow is installed. Your
vehicle can be damaged if either the front or rear
axle ratings or the Gross Vehicle Weight (GVW) are
exceeded.
Some vehicles are built with a special snow plow prep
package, called RPO VYU. If your vehicle has this
option, you can add a plow to it, provided certain
weights, such as the weights on the vehicle’s axles and
the Gross Vehicle Weight (GVW), are not exceeded.
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The plow your vehicle can carry depends on many
things, such as:
The options your vehicle came with, and the weight
of those options.
The weight and number of passengers you intend
to carry.
The weight of items you have added to your
vehicle.
The total weight of any additional cargo you intend
to carry.
Say, for example, you have a 700 lb (318 kg) snow
plow. The total weight of all occupants and cargo inside
the cab should not exceed 300 lb (135 kg). This
means that you may only be able to carry one
passenger. But, even this may be too much if you have
got other equipment already adding to the weight of
your vehicle.
Here are some guidelines for safely carrying a snow
plow on your vehicle:
Make sure the weight on the front and rear axles
does not exceed the axle rating for each.
For the front axle, if more cargo or passengers must
be carried, appropriate counter ballast must be
installed rear of the rear axle. Counter ballast must
be properly secured so it will not move during driving.
Follow the snow plow manufacturer’s
recommendations regarding rear ballast. Rear
ballast may be required to ensure a proper front and
rear weight distribution ratio, even though the actual
weight at the front axle may be less than the front
axle rating.
The snow plow manufacturer or installer can assist
you in determining the amount of rear ballast
required, to help make sure your snowplow/vehicle
combination does not exceed the GVW rating, the
front and rear axle ratings, and the front and rear
weight distribution ratio.
The total vehicle must not exceed the GVW rating.
Front axle reserve capacity is the difference between
your front Gross Axle Weight Rating (GAWR) and the
front axle weight of your vehicle with full fuel and
passengers. Basically, it is the amount of weight you can
add to your front axle before reaching your front GAWR.
The front axle reserve capacity for your vehicle can be
found in the lower right corner of the Certication/Tire
label, as shown.
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For example, adding a 700 lb (318 kg) snow plow
actually adds more than 700 lbs (318 kg) to the front
axle. Using the formula, if the snow plow is 4 ft (122 cm)
in front of the front axle and the wheel base is 10 ft
(305 cm), then:
W = 700 lb (318 kg)
A = 4 ft (122 cm)
W.B. = 10 ft (305 cm)
(W x (A + W.B.))/W.B. = (700 x (4 + 10))/10 = 980 lbs
(445 kg)
So, if your vehicle’s front axle reserve capacity is more
than 980 lbs (445 kg), you could add the snow plow
without exceeding the front GAWR.
You can add heavier equipment on the front of the vehicle
if you compensate for it by carrying fewer passengers,
less cargo, or by positioning cargo towards the rear. This
has the effect of reducing the load on the front. However,
the front GAWR, rear GAWR, and the Gross Vehicle
Weight Rating (GVWR) must never be exceeded.
{CAUTION:
On some vehicles that have certain front
mounted equipment, such as a snow plow, it
may be possible to load the front axle to the
front gross axle weight rating (GAWR) but not
have enough weight on the rear axle to have
proper braking performance. If your brakes can
not work properly, you could have a crash. To
help your brakes work properly when a snow
plow is installed, always follow the snow plow
manufacturer or installer’s recommendation for
rear ballast to ensure a proper front and rear
weight distribution ratio, even though the
actual front weight may be less than the front
GAWR, and the total vehicle weight is less
than the gross vehicle weight rating (GVWR).
Maintaining a proper front and rear weight
distribution ratio is necessary to provide
proper braking performance.
Total vehicle reserve capacity is the difference between
your GVWR and the weight of your vehicle with full
fuel and passengers. It is the amount of weight you can
add to your vehicle before reaching your GVWR.
4-44

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 have loaded the trailer, weigh the trailer and
then the tongue separately, to see if the weights
are proper. If they are not, you may be able to get them
right 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.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).
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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.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 seeLoading the Vehicle on page 4-35for 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.
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Service............................................................5-3
Accessories and Modications..........................5-3
California Proposition 65 Warning.....................5-4
California Perchlorate Materials Requirements.....5-4
Doing Your Own Service Work.........................5-4
Adding Equipment to the Outside
of the Vehicle.............................................5-5
Fuel................................................................5-5
Gasoline Octane............................................5-6
Gasoline Specications....................................5-6
California Fuel...............................................5-6
Additives.......................................................5-7
Fuel E85 (85% Ethanol)..................................5-8
Fuels in Foreign Countries...............................5-9
Filling the Tank............................................5-10
Filling a Portable Fuel Container.....................5-13
Checking Things Under the Hood....................5-14
Hood Release..............................................5-14
Engine Compartment Overview.......................5-16
Engine Oil...................................................5-17
Engine Oil Life System..................................5-20
Engine Air Cleaner/Filter................................5-22
Automatic Transmission Fluid
(4-Speed Transmission)..............................5-24Automatic Transmission Fluid
(6-Speed Transmission)..............................5-27
Engine Coolant.............................................5-31
Coolant Surge Tank Pressure Cap..................5-34
Engine Overheating.......................................5-34
Overheated Engine Protection Operating Mode . . .5-36
Cooling System............................................5-37
Engine Fan Noise.........................................5-41
Power Steering Fluid.....................................5-42
Windshield Washer Fluid................................5-43
Brakes........................................................5-44
Battery........................................................5-47
Jump Starting...............................................5-48
Rear Axle.......................................................5-54
Four-Wheel Drive............................................5-55
Front Axle......................................................5-56
Headlamp Aiming...........................................5-58
Bulb Replacement..........................................5-61
Halogen Bulbs..............................................5-61
Taillamps, Turn Signal, Stoplamps
and Back-up Lamps...................................5-61
License Plate Lamp......................................5-63
Replacement Bulbs.......................................5-63
Windshield Wiper Blade Replacement..............5-64
Section 5 Service and Appearance Care
5-1

Rear Axle
When to Check Lubricant
It is not necessary to regularly check rear axle uid
unless you suspect there is a leak or you hear an
unusual noise. A uid loss could indicate a problem.
Have it inspected and repaired.
All axle assemblies are lled by volume of uid during
production. They are not lled to reach a certain level.
When checking the uid level on any axle, variations in
the readings can be caused by factory ll differences
between the minimum and the maximum uid volume.
Also, if a vehicle has just been driven before checking the
uid level, it may appear lower than normal because uid
has traveled out along the axle tubes and has not drained
back to the sump area. Therefore, a reading taken ve
minutes after the vehicle has been driven will appear to
have a lower uid level than a vehicle that has been
stationary for an hour or two. Remember that the rear
axle assembly must be supported to get a true reading.
How to Check Lubricant
1500 Series
5-54