Permanent All-Wheel Drive, Function - GF28.00-P-0002AVN

Model 257 (except 257.361) with transmission 725.0 

up to model year 2021 

Courtesy of MERCEDES-BENZ USA

Block diagram 

Automatically-controlled all-wheel drive (4MATIC) in general 

The automatically controlled all-wheel drive (4MATIC) is a permanent all-wheel drive with interaxle differential.

The separate transfer case is fastened to the transmission housing and features the following design-related advantages:

• In case of defects, the transmissions (automatic transmission and transfer case) can be replaced or repaired separately. However, the opportunity to replace defined component parts means that a complete replacement of the transfer case is not necessarily required.
• Due to separate oil circuits (of the automatic transmission and the transfer case), there is no mutual impairment due to debris (e.g. due to metal abrasion)

The lubrication system is designed as splash lubrication without external cooling. The pre-lock torque of 40 to 50 Nm serves to improve traction at low engine torque while also helping to avoid any vibrations in the drivetrain. The gear ratio is designed such that 55 % of the engine torque is transferred to the rear axle and 45 % to the front axle (on vehicles with single planetary gear set) or 31 % of the engine torque to the front axle and 69 % to the rear axle (on vehicles with double planetary gear set). The drive torque is distributed via a single-speed transfer case without off-road ratio to the drive axles (drive train).

Further subfunctions are described in separate documents: 

• 4MATIC transfer case, function 
• Front axle transmission output 4MATIC function 
• 4MATIC front axle transmission, function 
• Oil supply for 4MATIC transfer case function 
• 4MATIC electronic traction system, function