2008 MERCEDES-BENZ GL550 differential

207 Controls in detail
Differential locks*
Start the engine (page 42).
To select the required locking mode,
rotate adjustment ring2 to the
desired position3 or4
(
page 205).
The indicator lamp on the adjustment
ring1 at the respective symbol
comes on.
Example illustration
5Center differential is completely locked
!If the differential locks have been manually
engaged, the tires will scuff on the road surface
when cornering because the differences be-
tween the individual wheel rotation speeds will
not be compensated for.
iThe differential locks are reset to AUTO
mode after the ignition has been switched off for
longer than 10 seconds.
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346 Operation
In the “Operation” section you will find
detailed information on operating, main-
taining and caring for your vehicle.
The first 1000 miles (1500 km)
The more cautiously you treat your vehicle
during the break-in period, the more satis-
fied you will be with its performance later
on.

Drive your vehicle during the first
1000 miles (1500 km) at varying but
moderate vehicle and engine speeds.

During this period, avoid heavy loads
(full throttle driving) and excessive
engine speeds (no more than
2/3 of
maximum rpm in each gear).

Shift gears in a timely manner.

Avoid accelerating by kick-down.

Do not attempt to slow the vehicle
down by shifting to a lower gear using
the gear selector lever.

Select gear ranges3, 2 or1
(
page 197) only when driving at
moderate speeds (for hill driving).After 1000 miles (1500 km) you may
gradually increase vehicle and engine
speeds to the permissible maximum.
All of the above instructions, as may apply
to your vehicle type, also apply when driv-
ing the first 1000 miles (1500 km) after
the engine, the transfer case, the center
differential or the rear differential has been
replaced.
iAlways obey applicable speed limits.
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356 Operation
Driving instructions
Read this chapter carefully before you be-
gin off-road travel.
Familiarize yourself with the vehicle char-
acteristics and gear changing before you
attempt any difficult terrain off-road driv-
ing. We recommend that you start out with
easy off-road travel.Special driving features for off-road
driving
The following driving features are available
for specific kind of operation:

Off-road – ABS (page 102)

Off-road – ESP® (page 106)

Off-road – 4-ETS (page 108)

Hill start assist system (page 196)

LOW RANGE mode* (page 201)

Differential locks* (page 204)

Downhill Speed Regulation (DSR)
(
page 273)

Off-road driving program (Vehicles
without enhanced off-road package*)
(
page 277)

Air suspension (page 278)Off-road driving rules

Engage the off-road driving program
(
page 277) or LOW RANGE mode*
(
page 201) before driving under
off-road conditions.

If necessary, activate differential
locks* (
page 204).

Make sure you select a vehicle level
(
page 279) appropriate to the topo-
graphical conditions. Always make
sure the vehicle has enough ground
clearance.

Fasten items being carried as securely
as possible (
page 295).

Always navigate gradients with the en-
gine on and with the transmission en-
gaged in a gear. Switch on the DSR
(
page 274) to help maintain a preset
speed.
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359 Operation
Driving instructions

Shift automatic transmission to
position1 (
page 197).

Drive slowly.

Avoid excessive engine speeds – drive
with moderate engine speeds
(max. 3 000 rpm).

Utilize the engine’s braking power
when descending a slope, observe the
engine speed (do not overrev the en-
gine). Apply the service brake as need-
ed.

Check the brakes after a lengthy down-
grade drive.Traction in steep terrain
The maximum vehicle climbing ability is a
100% grade which is equivalent to a slope
angle of 45 degrees. Keep in mind that the
climbing ability of the vehicle depends on
terrain conditions.
Be easy on the accelerator and watch for
continuous wheel traction when driving in
steep terrain.Driving across a hilltop
Decelerate just ahead of a hilltop (do not
shift automatic transmission to
positionN), to prevent the vehicle from
speeding up too much after climbing a hill.
Use the momentum of the vehicle to drive
across the hilltop.
After climbing a hill, driving in this manner
prevents the vehicle from:
losing ground contact when cresting
hills

losing its forward momentum

speeding up too much after climbing
the hill
iFor maximum engine speed, see “Instru-
ment cluster” (
page 26) and see “Engine”
(
page 553).
Warning!G
Never turn the vehicle around on steep
inclines. The vehicle might roll over. If the
vehicle cannot complete the attempted
climb, back it down in reverse gear.
iThe hill start assist system supports you
when driving uphill.
For more information, see “Hill start assist sys-
tem” (
page 196).
iThe 4-ETS helps greatly when starting out on
a steep incline when the front wheels have then
the tendency to slip due to the weight shifting
towards the rear axle.
The 4-ETS recognizes the situation and limits the
torque for the front wheels by braking them.
Simultaneously the torque for the rear wheels is
increased.
iVehicles with enhanced off-road package*
are equipped with automatic locks for the center
and rear axle differential to improve vehicle
traction.
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363 Operation
Driving instructions

Avoid high engine speeds.

Shift automatic transmission to
position1 (
page 197).

Drive next to the ruts rather than
through them if at all possible.

If the ruts are too deep to drive in, drive
with one side of the vehicle on the
grassy center strip if the route permits.Returning from off-road drivingOff-road driving increases strain on the
vehicle.
We recommend that you inspect the vehi-
cle for possible damage after each off-road
trip. Recognizing any damage and a subse-
quent timely repair reduces the chance of
a possible breakdown or accident later on.
Proceed as follows:

Switch off the off-road driving program
(
page 278) or the LOW RANGE
mode* (
page 201).

Switch off the DSR (page 274).

Set the differential locks* to AUTO
(
page 205).

Lower the vehicle back to a level
suitable for road conditions, e.g. High-
way/High-speed level (
page 279).

Clean all exterior lamps and check for
possible damage.
!Check that the ruts are not too deep and
your vehicle’s clearance is sufficient. Otherwise:

your vehicle may be damaged

the underbody of the vehicle may come in
contact with the ground and you may get
stuck
Warning!G
If you feel a sudden significant vibration or
ride disturbance, or you suspect that possi-
ble damage to your vehicle has occurred,
you should turn on the hazard warning flash-
ers, carefully slow down, and drive with cau-
tion to an area which is a safe distance from
the roadway.
Inspect the tires and under the vehicle for
possible damage. If the vehicle or tires ap-
pear unsafe, have it towed to the nearest
Mercedes-Benz Light Truck Center or tire
dealer for repairs.
Damage to the vehicle may influence driving
comfort and pose the risk of accident to you
and other drivers.
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488 Practical hints
What to do if …
Display symbolDisplay messagePossible cause/consequencePossible solution
kLocking System Inoperative
Service RequiredThe differential locks* are
malfunctioning.Do not drive faster than 50 mph
(80 km/h).
Have the vehicle checked at an autho-
rized Mercedes-Benz Light Truck
Center.
Diff. Lock System
Overheated - Wait briefly.The differential locks* are too hot
and have been deactivated as a re-
sult.Continue driving with added caution.
The lock function is unavailable.
Wait for the lock system to cool down.
The differential locks will be reactivat-
ed as soon as they have cooled down.
Stop vehicle,
engage parking brake.A shifting procedure could not be
completed. LOW RANGE* is in neu-
tral position. There is no connection
between the engine and the drive
wheels.Do not attempt to continue driving.
You could otherwise damage the
vehicle’s drivetrain.
Stop the vehicle in a safe location or
soon as it is safe to do so.
Engage the parking brake.
Perform the shifting procedure again
(
page 202).
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562 Technical data
Fuels, coolants, lubricants
Capacities
Vehicle components and their respective
lubricants must match. Therefore only use
products tested and approved by
Mercerdes-Benz.
Please refer to the Factory Approved
Service Products pamphlet (USA only), or
inquire at an authorized Mercedes-Benz
Light Truck Center.
Warning!G
Comply with all valid regulations with re-
spect to handling, storing and disposing of
service fluids. Otherwise you could
endanger persons or the environment.
Keep service fluids out of the reach of
children.
For health reasons, you should prevent
service fluids from coming into direct
contact with your skin or clothing.
If a service fluid is swallowed, contact a
physician immediately.
ModelCapacityFuels, coolants, lubricants, etc.
Engine with oil filterGL 320 CDI9.0 US qt (8.5 l)Approved engine oils
GL 450, GL 5509.5 US qt (9.0 l)Approved engine oils
Automatic transmissionAll models9.5 US qt (9.0 l)MB Automatic Transmission Fluid
Transfer case single speedAll models0.5 US qt (0.5 l)MB Automatic Transmission Fluid
Transfer case double speed*All models1.6 US qt (1.5 l)MB Automatic Transmission Fluid
Front axleAll models1.2 US qt (1.1 l)Hypoid gear oil
Rear axleAll models1.2 US qt (1.1 l)Hypoid gear oil
Rear axle with differential lock*All models1.7 US qt (1.6 l)Hypoid gear oil
Power steeringAll modelsapprox. 1.3 US qt (1.2 l)MB Power Steering Fluid or approved
Dexron III ATF
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575 Index
Corner-illuminating front fog lamps* 147
Messages in the multifunction
display 478
Replacing bulbs 510
Crossbars* 295
Crossing obstacles 361
Cruise control 255
Activating 257
Messages in the multifunction
display 452
Cup holders 320
Cleaning 321
Front center console 321
Front center console,
Removing/Installing 321
Rear armrest 320
Curb weight 416
D
Date display, Setting 174
Daytime running lamp mode 145
Setting 175
Deep water see Standing water
Defogging windshield 221, 235
Defrosting, Front 221, 235
Defrosting, Rear 212Delayed shut-off
Exterior lamps 176
Interior lighting 177
Department of Transportation see DOT
Diesel engine
Preglow indicator lamp 29
Differential locks* 204
A few words about 204
Messages in the multifunction
display 488
Switching 205
Difficulties
While driving 65
While starting 59
Digital clock see Clock
Digital speedometer 155, 163
Dimensions, Vehicle 560
Direction of rotation (tires) 387
Displays
Digital speedometer 155, 163
Distronic* 263
Maintenance service indicator 422
Messages in the multifunction
display 449
Multifunction display 155Outside temperature 155, 163
Selecting 173
Symbol messages 466
Text messages 451
Vehicle status message 168, 449
Vehicle system settings, Control
system 159, 161, 168
Distance to empty (range), Trip
Computer 184
Distronic* 260
Activating 266
Cleaning system sensor 430
Control system 264
Deactivating 268
Distance warning function* 272
Distance warning function*
activating/deactivating 183
Driving hints 270
Messages in the multifunction
display 453
Sensor cover 430
Warning and indicator lamps 263
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