Mercedes-Benz GLK-Class Service Manual page 57

Planetary gear differential
1 Side output drive gear with sun gear
2 Planet carrier with dual planetary gear set
4 Ring gear with transfer case drive shaft
When the vehicle is driving straight ahead, the input
and output shafts of the planetary gear set rotate at
the same speed. The planetary gear set rotates as a
block.
Relative movement between the sun gear and planet
carrier only takes place when there is an rpm differ-
ence at the wheels of the front and rear axle (e.g.
when cornering).
The planetary gears then roll between the sun gear
and ring gear, balancing the rpm.
The planetary gears are helically geared to reduce the
noise produced when the planetary gears turn.
56 v Introduction of the New GLK-Class (USA), Introduction into Service Manual for Model Series 204
6 Rear axle drive
7 Retaining ring
i
On vehicles with permanent all-wheel drive, a
central differential is required between the front
axle and rear axle to compensate for differences in
wheel speed. On vehicles with 4MATIC, this func-
tion is performed by the planetary gear differential.