Glossary
4 wheel Electronic Traction System
4ETS
Working with the vehicle's full-time four-wheel drive, 4-ETS uses individual wheel-speed sensors to detect the onset of wheel slip. Then it individually brakes the slipping wheels as needed, providing the effect of locking the front, center and/or rear differentials. The 4-ETS system continually balances the torque split to direct power to the wheel or wheels with traction.

4 Wheel Drive and Automatic
4MATIC
4MATIC is the name of a complex electronically controlled all wheel drive system developed and used by Mercedes-Benz on some of its models. All Mercedes cars featuring this system also have an automatic transmission in standard equipment and that's where its name is derived from (4-wheel drive and automatic transmission).

Originally developed together by Mercedes and Steyr-Daimler-Puch engineers, the system is now at its third generation but it's still based on a rear wheel drive chassis on most of the models. The system employs locking central and rear differentials to provide additional traction in slippery conditions or during off-roading. On the G-Klasse the system uses three locking differentials (front, central and rear).

Four Wheel Drive
4WD
Four Wheel Drive is a system which transfers engine power to four wheels independently and is mostly found on SUVs and all-terain vehicles. By using differentials it can transfer almost any amount of power percentage to any of the four driving wheels.
Two Wheel Drive
4X2
This expression is used to describe a vehicle with only two wheel drive. The first figure is the total number of wheels, and the second is the number of driving wheels. In some countries it's essentially a different name for rear-wheel drive vehicles (RWD), unlike 2X4, which can be used for describing a front-wheel drive vehicle (FWD).