Mercedes-Benz GL-Class 2008 Owners Manual - Manual (Page 205)

204
Controls in detail
Differential locks*
For more information on Off-road driving,
see “Off-road driving” (
୴ page 355).
Vehicles with enhanced off-road package*
are equipped with automatic locks for the
center and rear axle differential to improve
vehicle traction.
ț The center differential compensates
for differences in wheel rotation be-
tween the front and rear axle.
ț The rear axle differential compensates
differences between the rear wheels.
A few words about differentials and
differential locks*
When a vehicle negotiates a turn, wheels
on the outside of the curve must travel far-
ther and rotate faster than the inside
wheels. The differential, the operation of a
set of gears that allows the powered
wheels in a vehicle to turn at different
speeds, makes this essential function pos-
sible.
The drawback is that the differential also
sends most of the engine’s power to the
wheel with the least load or strain on it. For
example, if one of a vehicle’s powered
wheels sits on a patch of snow and spins
because there is no traction, all of the en-
gine’s power will go to that wheel because
the power will take the path of least resis-
tance. Meanwhile, the opposite wheel, sit-
ting on dry pavement where it could get
enough grip to start the vehicle moving,
sits idle because it receives no power.
The Electronic Traction System (ETS) ad-
dresses this problem and provides for
good control and steering ability by auto-
matically slowing the slipping wheel and
thus increasing the power to the other
non-slipping drive wheels to get the vehicle
moving. The ESP
® and ETS in this vehicle
feature such intelligent limited-slip differ-
ential technology, ideally suited for
on-road and light off-road driving. Transfer
case position LOW (
୴ page 201) also en-
hances off-road driving capabilities
(
୴ page 355).
More extreme off-road conditions may call
for another solution, engaging a differen-
tial lock or preventing the differential from
operating altogether. This vehicle comes
with two differential locks: transfer case
(center) and rear. Each can be engaged
simply by operating a rotary switch located
on the center console (
୴ page 205). When
the transfer case (center) differential is
locked, the combined (or average) speed
of the front wheels is identical to the com-
bined rear wheel speed. When the rear
differential is locked, both rear wheels turn
i At the front axles, the 4-ETS system
( ୴ page 107) compensates for any traction
problems.
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