2008 MERCEDES-BENZ GL550 ABS

199 Controls in detail
Automatic transmission
Downshifting
Briefly press left shift button1.
The transmission will shift to the next
lower gear as permitted by the shift
program. This action simultaneously
limits the gear range of the automatic
transmission (
page 197).Upshifting
Briefly press right shift button2.
The transmission will shift to the next
higher gear as permitted by the shift
program. This action simultaneously
extends the gear range of the automat-
ic transmission (
page 197).
Canceling gear range limit
Press and hold right shift button2
until the cipher for the current gear
range disappears from the multifunc-
tion display (
page 197).
The transmission will shift from the
current gear range directly to gear
rangeD.Shifting into optimal gear range
Press and hold left shift button1.
The transmission will automatically
select the gear range suited for optimal
acceleration and deceleration. This will
involve shifting down one or more
gears.
Warning!G
On slippery road surfaces, never downshift
in order to obtain braking action. This could
result in drive wheel slip and reduced
vehicle control. Your vehicle’s ABS will not
prevent this type of loss of control.
iTo avoid overrevving the engine when down-
shifting, the transmission will not shift to a lower
gear if the engine’s max. speed would be ex-
ceeded.
iIf you press on the accelerator when the
engine has reached its rpm limit, the transmis-
sion will upshift beyond any gear range limit
selected.
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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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205 Controls in detail
Differential locks*
at the same speed, independent of the in-
dividual torque. Please be aware that en-
gaging the differential locks will
significantly reduce the steering ability of
the vehicle.
For your safety and the safety of others
and to prevent damage to the vehicle, the
differential locks must not be engaged
when driving on paved roads. It is impor-
tant to understand that during
on-road/paved driving, differentials are
absolutely necessary for providing the es-
sential control and steering ability of the
vehicle. The differential locks, therefore,
must not be engaged when driving on
paved roads and should only be used to
the extent necessary to negotiate off-road
conditions which cannot be handled by the
systems (automatic 4-ETS, the ESP
®, man-
ual switch position “LOW” of transfer case)
this vehicle comes equipped with.
Switching differential locks*The rotary switch for the differential locks
is located on the upper part of the center
console.
You can select between three locking
modes.
1Rotatable outer adjustment ring with
indicator lamp
2AUTO mode: center differential is auto-
matically locked
3Center differential is completely locked
4Center and rear axle differential are
completely locked
!If the differential locks are engaged, accel-
erate gently when setting the vehicle in motion.
To avoid damage to the transmission, the vehicle
may only be operated on a dynamometer (single
axle dynamometer) if

the axle not being driven is jacked up
or

the associated propeller shaft is disconnect-
ed.
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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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255 Controls in detail
Driving systems
Driving systems
The driving systems of your vehicle are
described on the following pages:

Cruise control (page 255) and
Distronic* (
page 260), with which
the vehicle can maintain a preset
speed.

Distance warning function*
(
page 272) is only available with
Distronic*, which warns of stationary
obstacle or slower moving vehicles that
you are closing in on too quickly.

Downhill Speed Regulation (DSR)
(
page 273), which supports you
when you are driving downhill.

Off-road driving program (page 277)
(vehicles without enhanced off-road
package*), which supports you when
you are driving off-road.

Air suspension program
There are two components available.

Vehicle level control (page 279),
which controls the vehicle level.

Adaptive Damping System (ADS)*
(
page 278), which adjusts the
vehicle suspension characteristics.

Parktronic* (page 288) and rear view
camera* (
page 293), which serve as
a parking aid.
For information on the ABS, BAS, EBP,
ESP
®, and 4-ETS, see “Driving safety sys-
tems” (
page 101).
Cruise control
The cruise control automatically maintains
the speed you set for your vehicle.
The use of cruise control is recommended
for driving at a constant speed for extend-
ed periods of time. You can set or resume
cruise control at any speed above
20 mph (30 km/h).
The cruise control function is operated by
means of the cruise control lever.
The cruise control lever is the uppermost
lever on the left-hand side of the steering
column (
page 24).
iThe cruise control should not be activated
during off-road driving.
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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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347 Operation
Driving instructions
Driving instructions
Drive sensibly – save fuel
Fuel consumption, to a great extent,
depends on driving habits and operating
conditions.
To save fuel you should:

Keep tires at the recommended infla-
tion pressures.

Remove unnecessary loads.

Remove carriers* when not in use.

Remove the crossbars* when not in
use.

Allow engine to warm up under low
load use.

Avoid frequent acceleration and decel-
eration.

Have all maintenance work performed
at the intervals specified in the
Maintenance Booklet and as required
by the Maintenance System. Contact
an authorized Mercedes-Benz Light
Truck Center.Fuel consumption is also increased by
driving in cold weather, in stop-and-go traf-
fic, on short trips and in hilly areas.
Drinking and driving
Pedals
Warning!G
Drinking and driving and/or taking drugs
and driving are a very dangerous combina-
tion. Even a small amount of alcohol or
drugs can affect your reflexes, perceptions
and judgment.
The possibility of a serious or even fatal
accident are greatly increased when you
drink or take drugs and drive.
Do not drink or take drugs and drive or allow
anyone to drive who has been drinking or
taking drugs.
Warning!G
Make sure that absolutely no objects are ob-
structing the pedal’s range of movement.
Keep the driver’s footwell clear of all obsta-
cles. If there are any floormats or carpets in
the footwell, make sure that the pedals still
have sufficient clearance.
During sudden driving or braking maneu-
vers, the objects could get caught between
the pedals. You could then no longer brake
or accelerate. This could lead to accidents
and injury.
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354 Operation
Driving instructions
Road salts and chemicals can adversely af-
fect braking efficiency. Increased pedal
force may become necessary to produce
the normal brake effect.
Depressing the brake pedal periodically
when traveling at length on salt-strewn
roads can bring road-salt-impaired braking
efficiency back to normal.If the vehicle is parked after being driven
on salt-treated roads, the braking efficien-
cy should be tested as soon as possible af-
ter driving is resumed.
For more information, see “Winter driving”
(
page 420).
Warning!G
On slippery road surfaces, never downshift
in order to obtain braking action. This could
result in drive wheel slip and reduced vehi-
cle control. Your vehicle’s ABS will not pre-
vent this type of control loss.
Do not engage the transfer case in position
LOW when driving on ice or packed snow. At
speeds below 18 mph (30 km/h) vehicle
steering is adversely affected by the
Off-road – ABS (
page 102).
Warning!G
Make sure not to endanger any other road
users when carrying out these braking
maneuvers.
Warning!G
If the vehicle becomes stuck in snow, make
sure that snow is kept clear of the exhaust
pipe and from around the vehicle with the
engine running. Otherwise, deadly carbon
monoxide (CO) gases may enter vehicle in-
terior resulting in unconsciousness and
death.
To assure sufficient fresh air ventilation,
open a window slightly on the side of the ve-
hicle not facing the wind.
Warning!G
The outside temperature indicator is not de-
signed to serve as an ice-warning device and
is therefore unsuitable for that purpose. In-
dicated temperatures just above the freez-
ing point do not guarantee that the road
surface is free of ice.
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