Basic Function Of Automatically Controlled All-Wheel Drive - GF28.00-P-9900A

Vehicles with all-wheel drive 

Overview 

This document contains information on:

• General 
• Function 
  • Vehicles with transversely mounted engine and dual-clutch transmission 
  • Vehicles with longitudinally mounted engine and automatic transmission 
  • Electric vehicles 
  • Hybrid vehicles 

General 

Contrary to front wheel drive or rear wheel drive, the drive force is forwarded to all wheels in all-wheel drive. Traction increases and improved off-road capability is achieved.

For automatic controlled all-wheel drive, there is a distinction between the following equipment variants:

• Vehicles with transversely mounted engine and dual-clutch transmission
• Vehicles with longitudinally mounted engine and automatic transmission
• Electric vehicles
• Hybrid vehicles

Function 

Vehicles with transversely mounted engine and dual-clutch transmission 

Example illustration of drivetrain, shown on model 247 

Courtesy of MERCEDES-BENZ USA

The power take-off distributes the torque to the rear axle and is integrated into the dual-clutch transmission (1). The torque is output to the rear axle variably depending on the driving situation and the wheel slip of the front wheels. The power take-off compensates differences in RPM between the front and rear wheels which occur in all-wheel mode while cornering.

Depending on the following situations, torque is distributed to the rear axle:

• Dynamic cornering
• Wide open throttle acceleration
• Extremely varying road surfaces

Vehicles with longitudinally mounted engine and automatic transmission 

Courtesy of MERCEDES-BENZ USA

Schematic diagram of drive torque distribution, shown on model 167 

For vehicles with longitudinally mounted engine and transmission, the torque distribution is predefined by the transfer case (16). Active-selective brake application takes over the function of the differential lock and vehicle dynamics control. The automatically regulated all-wheel drive is usually a permanent all-wheel drive with fixed force distribution.

Electric vehicles 

Courtesy of MERCEDES-BENZ USA

Example illustration of drivetrain, shown on model 293 

In electric vehicles, all-wheel drive is made possible on the front axle or rear axle on a vehicle-specific basis by an additional electric machine (29, 30).

The type of electric machine (29, 30) varies depending on the model series.

All electric vehicles with all-wheel drive function are equipped with an additional electric drivetrain that can be controlled independently by the electric drivetrain of the non-all-wheel drive variant.

The electric drivetrain, that is also operated for all-wheel drive function, can be switched on and off for efficiency and range.

Hybrid vehicles 

All-wheel drive on hybrid vehicles is a mixture of the all-wheel drive function in the combustion engine and in electric machines.

Depending on the state of charge of the high-voltage battery, all-wheel drive is guaranteed either by the two electric machines or the combustion engine.

	Additional basic functions
	Basic function of all-wheel drive with dual-clutch transmission	Model all with transmission 700.4, 724.0/1 with code M005 (Vehicles with 4MATIC/all-wheel drive)	GF28.00-P-1000A
	Basic function of all-wheel drive with automatic transmission	Model all with transmission 725.0/1 with code M005 (Vehicles with 4MATIC/all-wheel drive) Model all with transmission 725	GF28.00-P-1001A
	All-wheel drive with electric drive, basic function	Electric vehicles with code M005 (Vehicles with 4MATIC/all-wheel drive)	GF28.00-P-1003A