2008 MERCEDES-BENZ GL550 tow

128 Controls in detail
Locking and unlocking
Automatic central locking
The doors and the tailgate lock automati-
cally when the ignition is switched on and
the wheels are turning at vehicle speeds of
approximately 9 mph (15 km/h) or more.
For information on towing the vehicle, see
“Towing the vehicle” (
page 538).
You can deactivate the automatic central
locking mode using the control system
(
page 180).
Locking and unlocking from the inside
You can lock or unlock the doors and the
tailgate from inside using the central lock-
ing or unlocking switch. This can be useful,
for example, if you want to lock the vehicle
before starting to drive.
The fuel filler flap cannot be locked or un-
locked with the central locking or unlock-
ing switch.Even with the SmartKey with KEYLESS-GO*
removed from the vehicle, the tailgate
closing switch can be operated. Therefore,
do not leave children unattended in the vehi-
cle, or with access to an unlocked vehicle. A
child’s unsupervised access to a vehicle
could result in an accident and/or serious
personal injury.
iTo prevent a possible inadvertent lockout,
the tailgate will open automatically if a SmartKey
with KEYLESS-GO* is recognized inside the
vehicle.
iYou can open a locked door from the inside.
Open door only when conditions are safe to do
so.
iThe doors unlock automatically after an
accident if the force of the impact exceeds a
preset threshold.
The vehicle automatically locks when the ignition
is switched on and the wheels are turning at
vehicle speeds of approximately 9 mph
(15 km/h) or more. You could therefore lock
yourself out when the vehicle

is pushed or towed

is on a test stand
Warning!G
When leaving the vehicle, always remove the
SmartKey or SmartKey with KEYLESS-GO*
from the starter switch, take it with you, and
lock the vehicle. Do not leave children unat-
tended in the vehicle, or with access to an
unlocked vehicle. A child’s unsupervised
access to a vehicle could result in an
accident and/or serious personal injury.

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194 Controls in detail
Automatic transmission
If you want the gear position to remain in
neutral positionN, e.g. when taking the
vehicle through an automatic conveyor
type car wash, observe the following
instructions.Vehicles with SmartKey:
With the vehicle at a standstill and the
ignition switched on shift the automatic
transmission to neutral positionN.
If engaged, release the parking brake
(
page 59).
Switch off the ignition and leave the
SmartKey in the starter switch.
Vehicles with KEYLESS-GO*:
With the vehicle at a standstill, depress
the brake pedal and keep it pressed.
With the ignition switched on shift the
automatic transmission to park
positionP.
Release the brake pedal.
Remove the KEYLESS-GO* start/stop
button from the starter switch
(
page 43).
Effect
íReverse gear
Shift into reverse gearR only
when the vehicle is stopped.
ëNeutral
No power is transmitted from the
engine to the drive axle. When
the brakes are released, the
vehicle can be moved freely
(pushed or towed).
To avoid damage to the transmis-
sion, never shift into neutral
positionN while driving.
If the ESP
® is deactivated or
malfunctioning:
Shift into neutral positionN only
if the vehicle is in danger of
skidding, e.g. on icy roads.
!If you turn off the engine using the
SmartKey or the KEYLESS-GO* start/stop
button, the transmission will shift to neutral
positionN automatically.
Warning!G
When leaving the SmartKey or SmartKey
with KEYLESS-GO* in the starter switch, do
not leave children unattended in the vehicle.
It is possible for children to switch on the
ignition which could result in unsupervised
use of vehicle equipment.
A child’s unsupervised access to a vehicle
could result in an accident and/or serious
personal injury.
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195 Controls in detail
Automatic transmission
Insert the SmartKey with
KEYLESS-GO* into the starter switch.
Switch on the ignition.
Depress the brake pedal.
Shift the automatic transmission to
neutral positionN.
Release the brake pedal.
If engaged, release the parking brake
(
page 59).
Switch off the ignition and leave the
SmartKey with KEYLESS-GO* in the
starter switch.
Driving tips
Accelerator position
Your driving style influences the
transmission’s shifting behavior:
Less throttle Earlier upshifting
More throttle Later upshifting
!Observe instructions

when taking the vehicle through an
automatic conveyor type car wash
(
page 428)

when towing the vehicle (page 538)
!Coasting the vehicle, or driving for any other
reason in neutral positionN can result in
transmission damage that is not covered by the
Mercedes-Benz Limited Warranty.
Effect
êDrive
The transmission shifts
automatically. All forward gears
are available.
Warning!G
Getting out of your vehicle without shifting
into park positionP is dangerous. Also, park
positionP alone is not intended to or capa-
ble of preventing your vehicle from moving,
possibly hitting people or objects.
Always set the parking brake in addition to
shifting to positionP (
page 67).
When parked on an incline, turn the front
wheels towards the road curb.
Do not park this vehicle in areas where com-
bustible materials such as grass, hay or
leaves can come into contact with the hot
exhaust system, as these materials could be
ignited and cause a vehicle fire.
Warning!G
When leaving the vehicle, always remove the
SmartKey or SmartKey with KEYLESS-GO*
from the starter switch, take it with you, and
lock the vehicle. Do not leave children unat-
tended in the vehicle, or with access to an
unlocked vehicle. Children could shift the
automatic transmission out of park
positionP, which could result in an accident
and/or serious personal injury.
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197 Controls in detail
Automatic transmission
On uphill grades with a gradient angle of
more than 5°, the hill start assist system
maintains the pressure in the brake sys-
tem for approximately 1 second after you
have released the brake pedal. Therefore,
you can start off smoothly without the
vehicle moving immediately after releasing
the brake pedal.
The hill start assist system is inactive

when starting off on a level road or
downhill grades

with the transmission in neutral
positionN

with the parking brake set

if the ESP® has switched off due to a
malfunctionTowing a trailer
If you tow a trailer, note the following
points:

Manually shift to a lower gear range
(
page 197) if the transmission hunts
between gears on inclines.
A lower gear range and reduction of
speed reduces the chance to overload
or overheat the engine.
For more information on trailer towing, see
the “Operation” section (
page 364).
Gear ranges
With the automatic transmission in drive
positionD, you can select a gear range for
the automatic transmission to operate
within.
You can limit the gear range by pressing
the left gearshift button on the steering
wheel gearshift control, and reverse the
gear range limit by pressing the right gear-
shift button on the steering wheel gearshift
control (
page 198).The selected gear range appears in the
multifunction display.
1Current gear range
Effect
ïThe transmission shifts through
sixth gear only.
îThe transmission shifts through
fifth gear only.
éThe transmission shifts through
fourth gear only.
èThe transmission shifts through
third gear only.
With this selection you can use
the braking effect of the engine.
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201 Controls in detail
Transfer case
Transfer case
LOW RANGE mode*
The LOW RANGE mode is available on vehi-
cles with enhanced off-road package*.
In the following situations you should
switch to LOW RANGE mode:

during off-road driving (page 355)

when crossing water (page 360)

when towing up or down on steep
gradients
With the LOW RANGE selected, the
engine’s power delivery and the shifting
behavior of the automatic transmission are
adjusted. Furthermore, the ABS, ESP
® and
4-ETS functions especially adapted to
off-road travel are activated.
For information on driving safety systems
during LOW RANGE mode, see “Driving
safety systems” (
page 101).
For more information on Off-road driving,
see “Off-road driving” (
page 355).Gear Ranges
There are two possible settings.
!Operational or performance test must only
be conducted on a two-axle dynamometer. If
such tests are necessary, contact an authorized
Mercedes-Benz Light Truck Center. You could
otherwise seriously damage the brake system or
the transfer case which is not covered by the
Mercedes-Benz Limited Warranty.
!Because the ESP® operates automatically,
the engine and ignition must be shut off
(SmartKey in starter switch position0 or1 or
KEYLESS-GO* start/stop button in
position0or1) when testing the parking brake
on a brake test dynamometer and such testing
should be no longer than 10 seconds.
Active braking action through the ESP
® may
otherwise seriously damage the brake system
which is not covered by the Mercedes-Benz
Limited Warranty.
iThe vehicle is equipped with permanent
four-wheel drive. Both the front and rear axles
are powered at all times when the vehicle is
being operated.
HIGH
RANGERoad position for all normal
driving situations.
(LOW RANGE mode off)
LOW
RANGEOff-road position for traveling
on rough terrain.
(LOW RANGE mode on)
Also use the off-road position
when driving on-road on steep
gradients, especially when
towing a trailer.
LOW RANGE acts by raising
the engine’s gear ratio. The ve-
hicle travels at roughly third
the speed compared to when
in the HIGH RANGE position,
leading to an increase in the
engine’s drive power.
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206 Controls in detail
Differential locks*
AUTO mode
The AUTO mode is adequate for most driv-
ing situations since the center differential
is locked and released as required.
Start the engine (page 42).
The center differential locks is in AUTO
mode. The indicator lamp on the
adjustment ring1 above
symbolU2 is on.Center and rear axle differential locksThe differential locks should only be
engaged manually if traction is insufficient
in AUTO mode.
The differential locks can be engaged in
the sequence3, 4 (
page 205) up to a
speed of 19 mph (30 km/h).
Engaging differential locks:

for off-road driving

for driving through water

when driving on deep snow and icy or
fouled surfaces
iAt speeds up to 19 mph (30 km/h), it is
possible to manually lock the differential locks
for driving on rough terrain.
Warning!G
Never drive on a paved surface with the
center and rear axle differential locks
manually engaged. Ability to steer the
vehicle is greatly reduced when the differen-
tial locks are manually engaged, increasing
the risk of an accident.
For safety reasons, the locks are automati-
cally released at a vehicle speed above
31 mph (50 km/h). Nevertheless, you
should only manually lock the differential if
absolutely necessary because engaged
locks will restrict the vehicle drive train
while cornering and cause the vehicle to
chatter. This could cause you to lose control
of the vehicle and cause an accident.
!The differential locks must not be engaged
manually when towing the vehicle or spinning the
wheels.
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208 Controls in detail
Good visibility
For information on windshield wipers, see
“Windshield wipers” (
page 62).
Headlamp cleaning system*
The headlamps will automatically be
cleaned with a high-pressure water jet
when you have

switched on the headlamps
and

operated the windshield wipers with
windshield washer fluid five times
When you switch off the headlamps, the
counter resets.
For information on filling up the washer
reservoir, see “Windshield/rear window
washer system and headlamp cleaning
system*” (
page 383).
Rear view mirrors
For more information on setting the rear
view mirrors, see “Mirrors” (
page 51).
Interior rear view mirror, antiglare
position
1Lever
Tilt the mirror to the antiglare position
by moving lever1 towards the wind-
shield.
The interior rear view mirror is dimmed.Auto-dimming rear view mirrors*
The reflection brightness of the exterior
rear view mirror on the driver’s side and
the interior rear view mirror will respond
automatically to glare when

the ignition is switched on
and

incoming light from headlamps falls on
the sensor in the interior rear view
mirror
The rear view mirror will not react if

the automatic transmission is set to
positionR

the interior lighting is turned on
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277 Controls in detail
Driving systems
Adjustment in 5 mph
(Canada: 10 km/h) increments
Increase set speed:
Briefly lift the cruise control lever up
past the resistance point in direction of
arrow1 (
page 276).
Release the cruise control lever.
The vehicle speed increases in incre-
ments of 5 mph (Canada: 10 km/h).
Reduce set speed:
Briefly press the cruise control lever
down past the resistance point in direc-
tion of arrow2 (
page 276).
Release the cruise control lever.
The vehicle speed decreases in incre-
ments of 5 mph (Canada: 10 km/h).
Each time the set speed is changed,
DSR will appear in the multifunction dis-
play and the newly set speed is shown.Off-road driving program (Vehicles
without enhanced off-road package*)
The off-road driving program is designed to
assist the driver when driving off-road in
terrain and crossing water. The off-road
driving program adjusts the engine power
and shifting of the automatic transmission
to be more suitable for the off-road use of
the vehicle. In addition, the ABS, ESP
®, and
4-ETS designed for off-road use are
automatically activated.
In the following situations you should
switch to the off-road driving program:

during off-road driving

when crossing water (page 360)

when towing up or down on steep
gradients
iThe set value is increased or decreased in
5 mph (Canada: 10 km/h) increments each time
you lift or depress the cruise control lever past
the resistance point.
iThe new speed is set and the vehicle will
accelerate or decelerate. Keep in mind that it
may take a brief moment until the vehicle has
reached the new set speed.
iThe set speed is canceled when DSR is
switched off. If DSR is switched on again, DSR
will use the programmed default speed
(
page 183).
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