2008 MERCEDES-BENZ GL450 Towing

367 Operation
Driving instructions
Make sure the automatic transmission
is set toP (
page 191).
Set the parking brake for the vehicle
(
page 67).
Start the engine (page 56).
Set the vehicle level to Highway
(
page 279).
Vehicle with ADS*: Set the ADS* to
AUTO or COMFORT (
page 278).
Turn off the engine (page 68).
Close all doors and the tailgate.
Attach the trailer.
Plug in all electrical connectors.
Towing a trailer
There are many different laws, including
speed limit restrictions, having to do with
trailer towing. Make sure your rig will be le-
gal, not only for where you reside, but also
for where you will be driving. A good
source for this information can be the po-
lice or local authorities.Note the following points, when driving
with the trailer:
In order to gain skill and an understand-
ing of the vehicle’s behavior, you
should practice turning, stopping and
backing up in an area which is free from
traffic.

Before you start driving check the

trailer hitch

break-away switch

safety chains

electrical connections

lighting and tires

Adjust the mirrors (page 51) to
permit unobstructed view beyond rear
of trailer.

If the trailer has electric brakes, start
your vehicle and trailer moving slowly,
and then apply only the trailer brake
controller by hand to make sure the
brakes are working properly.
!Do not connect a trailer brake system (if
trailer is so equipped) directly to the vehicle’s
hydraulic brake system, as your vehicle is
equipped with antilock brakes. If you do, neither
the vehicle’s brakes nor the trailer’s brakes will
function properly.
iThe provided vehicle electrical connector for
trailer towing has a brake signal wire for hook-up
to a brake controller.
You should consider using a trailer sway control
system. For further information, contact an
authorized Mercedes-Benz Light Truck Center.
iWhen you are towing a trailer, the vehicle
level always remains in the Highway setting.
The following applies additionally when towing a
trailer:

The vehicle is lowered to the highway level
when it reaches a speed of 5 mph (8 km/h)
if not set to highway level.

The high-speed level is not available.
The restrictions that apply to towing also apply
when using accessories that are connected to
the trailer power socket, such as a bicycle rack.
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368 Operation
Driving instructions

Always secure items in the trailer to
prevent load shifts while driving.

When towing a trailer, check occasion-
ally to make sure the load is secure,
and that lighting and trailer brakes (if
so equipped) are functioning properly.

Take into consideration that when tow-
ing a trailer, the handling characteris-
tics are different and less stable from
those when operating the vehicle with-
out a trailer.
It is important to avoid sudden maneu-
vers.

The vehicle and trailer combination is
heavier, and therefore is limited in ac-
celeration and climbing ability, and re-
quires longer stopping distances.
It is more prone to reacting to cross
wind gusts, and requires more sensi-
tive steering input.

If possible, do not brake abruptly, but
rather engage the brake slightly at first
to permit the trailer to activate its
brake. Then increase the braking force.

If the transmission repeatedly shifts
between gears on inclines, manually
shift to a lower gear (select 4, 3, 2 or 1)
(
page 197).
A lower gear and reduction of speed re-
duces the chance of engine overload-
ing and/or overheating.

On very steep inclines, not manageable
with automatic transmission in1,
switch on off-road driving program
(
page 278) or LOW RANGE mode*
(
page 201).

When going down a long hill, shift into
a lower gear and use the engine’s brak-
ing effect.
Avoid riding the brakes, thus overheat-
ing the vehicle and trailer brakes.

If the engine coolant rises to an ex-
tremely high temperature (coolant tem-
perature needle approaching the red
zone) when the air conditioning is on,
turn off the air conditioning system.
Engine coolant heat can be additionally
vented by opening the windows,
switching the climate control fan speed
to high and setting the temperature
control to the maximum hot position.

Extreme care must be exercised since
your vehicle with a trailer will require
additional passing distance ahead than
when driving without a trailer.
Because your vehicle and trailer is
longer than your vehicle alone, you will
also need to go much farther ahead of
the passed vehicle before you can re-
turn to your lane.
!If the trailer should begin to sway, reduce
the vehicle’s speed immediately.
In no case attempt to straighten out the tow
vehicle and trailer by increasing the speed.
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390 Operation
Tires and wheels
Step 4
The resulting figure equals the avail-
able amount of cargo and luggage load
capacity. For example, if the “XXX”
amount equals 1400 lbs and there will
be five 150 lbs passengers in your
vehicle, the amount of available cargo
and luggage load capacity is 650 lbs
(1400-750 (5 x150) = 650 lbs).
Step 5
Determine the combined weight of
luggage and cargo being loaded on the
vehicle. That weight may not safely
exceed the available cargo and luggage
load capacity calculated in step 4.Step 6 (if applicable)
If your vehicle will be towing a trailer,
load from your trailer will be trans-
ferred to your vehicle. Consult this
manual to determine how this reduces
the available cargo and luggage load
capacity of your vehicle (
page 392).
The following table shows examples on
how to calculate total and cargo load
capacities with varying seating configura-
tions and number and size of occupants.
The following examples use a load limit
of 1500 lbs. This is for illustration
purposes only. Make sure you are using
the actual load limit for your vehicle stated
on the vehicle’s Tire and Loading
Information placard (
page 388).

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435 Practical hints
What to do if …
Where will I find ...?
Unlocking/locking in an emergency
Resetting activated head restraints
Replacing SmartKey batteries
Replacing bulbs
Replacing wiper blades
Flat tire
Bleeding the fuel system
(diesel engine only)
Battery
Jump starting
Towing the vehicle
Fuses
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486 Practical hints
What to do if …
Display symbolDisplay messagePossible cause/consequencePossible solution
nLevel Selection
Not PermittedThe selected vehicle level cannot adjust-
ed, because

you are driving too fast for the desired
vehicle level

you are towing a trailer

you are using accessories that are
connected to the trailer power socket,
e.g. a bicycle rack
Reduce vehicle speed.
Set the desired vehicle level again
(
page 279).
MalfunctionThe air suspension is malfunctioning.Do not drive faster than 50 mph
(80 km/h) depending on the set vehi-
cle level.
Have the vehicle checked at an autho-
rized Mercedes-Benz Light Truck
Center.
Compressor
Cooling DownYou have selected a higher vehicle level.
Due to frequent level changes within a
short period, the compressor must first
cool down.Let the compressor cool until the
message disappears.
The selected level will be set once the
compressor has cooled down.
!When the message Compressor Cooling
Down
appears in the multifunction display,
driving is still possible. Keep in mind that theride height of the vehicle is not yet reached, so
you can damage the underbody of the vehicle.The selected level will be set once the compres-
sor has cooled.
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490 Practical hints
Where will I find ...?
First aid kit
The first aid kit is located on the driver’s
side in the cargo compartment behind the
cover.
1Lock
2Cover in left side trim panel
Turn lock1 90° in direction of arrow.
Fold down cover2.
The first aid kit can be removed.
Vehicle tool kit
The vehicle tool kit is stored under the
cargo compartment floor.
The vehicle tool kit includes:

Towing eye bolt

Wheel wrench

Alignment bolt

Vehicle jack

Fuse chart

Collapsible wheel chock

Wheel bolts for spare wheel1Cargo compartment floor, lowered
2Handle cover
Open the tailgate (page 122).
Push in handle cover2 as indicated
by arrow and pull handle.
Lift cargo compartment floor1.
iCheck expiration dates and contents for
completeness at least once a year and replace
missing/expired items.
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492 Practical hints
Where will I find ...?
Example illustration1
6Alignment bolt
7Towing eye bolt
8Wheel wrench
9Hook and loop fastener
aVehicle jack
2
bWheel bolts
cCollapsible wheel chock
dFuse chart
eVehicle tool kit storage well casing
To remove vehicle jacka, loosen
hook and loop fastener9.Vehicle jack
The vehicle jack is located underneath the
cargo compartment floor.
1Depending on production date, your vehicle may
be equipped with a scissors-type vehicle jack.
Thus, appearance and alignment of the items may
vary.
2If your vehicle is equipped with a scissors-type
vehicle jack, a reversible ratchet is also included.
!Depending on vehicle production date your
vehicle may be equipped with a scissors-type
jack (located under the cargo compartment
floor). If so equipped, only use this jack when
jacking up the vehicle as otherwise the vehicle’s
underbody can be damaged. See separate
instructions for scissors-type jack.
!To prevent damage, always disengage the
strap of the securing hook and lower the cargo
compartment floor (
page 490) before closing
the tailgate.
Warning!G
Only use the jack supplied with your vehicle
to lift the vehicle briefly for wheel changes.
If you use the jack for any other purpose,
you or others could be inj ure d, as the ja ck is
designed only for the purpose of changing a
wheel.
When using the jack, observe the safety
notes in the “Mounting the spare wheel”
section (
page 520) and the notes on the
jack.
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538 Practical hints
Towing the vehicle
Mercedes-Benz recommends that the
vehicle be transported with all wheels off
the ground using flatbed or appropriate
wheel lift/dolly equipment. This method is
preferable to other types of towing.If circumstances do not permit the recom-
mended towing methods, the vehicle may
be towed with all wheels on the ground
only so far as necessary to have the vehicle
moved to a safe location where the recom-
mended towing methods can be employed.
When towing the vehicle with all wheels on
the ground, the vehicle may be towed only
for distances up to 30 miles (50 km) and at
a speed not to exceed 30 mph (50 km/h).
!Do not tow-start the vehicle.
!Use flatbed or wheel lift/dolly equipment,
with the SmartKey in starter switch turned to
position0.
Do not tow with sling-type equipment. Towing
with sling-type equipment over bumpy roads will
damage radiator and supports.
To prevent damage during transport, do not tie
down vehicle by its chassis or suspension parts.
Use the towing eyes.
Switch off the ESP
® (page 105) and the
automatic central locking (
page 128).
!Do not tow with one axle raised. Doing so
could damage the transfer case, which is not
covered by the Mercedes-Benz Limited
Warranty.
All wheels must be on or off the ground. Observe
instructions for towing the vehicle with all
wheels on the ground.
Warning!G
If circumstances require towing the vehicle
with all wheels on the ground, always tow
with a tow bar if

the engine will not run

there is a malfunction in the brake
system

there is a malfunction in the power
supply or in the vehicle’s electrical
system
This is necessary to adequately control the
towed vehicle.
Prior to towing the vehicle with all wheels on
the ground, make sure the automatic trans-
mission is in neutral positionN.
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