Fig. 6.24. Transmission diagram of the 4Matic model: 1 – cardan shaft (to the rear axle differential); 2 – transfer case; 3 – gearbox with cylindrical gear transmission for the front axle; 4 – cardan shaft (to the front axle differential); 5 – front axle differential; 6 – front wheel drive shaft
All-wheel drive in the new 4Matic version is carried out via a permanently connected single-stage transfer case 2 (Fig. 6.24) only mechanically with a constant distribution of torque in the ratio: 65% to the rear axle and 35% to the front.
The function of equalizing the torque between the axles is performed by a central differential with a double planetary mechanism. The drive to the front wheels is carried out by a reducer with a cylindrical gear transmission and improved anti-noise characteristics, which also functions as an oil pump and provides the lubrication system of the transfer case.
The differential lock function is performed by the electronic anti-slip system ETS, which regulates the amount of torque on individual wheels, reducing it by braking and simultaneously increasing the traction force on other wheels.
In addition to this, the ESP electronic stability control system, which has proven itself in other Mercedes models, monitors all four wheels on 4Matic models when sensors detect a critical wheel grip situation – for example, when cornering or overtaking on slippery surfaces.
In addition, the so-called Brake Assist System (BAS), which has been standard on all Mercedes model series since 1997, is integrated into this comprehensive control system. This concerns control in emergency braking situations. Harsh braking in a critical situation is assessed by an electronic device based on the speed at which the pedal is pressed. From this point on, the electronics take over control to ensure the most effective braking until the driver begins to control the force on the pedal (see also section "Brake system").
Diagnostics and troubleshooting of ETS, ESP and BAS systems are in any case the domain of specialists. Even a routine oil change in the transfer case and front axle differential is no longer necessary. Both units use a working fluid with a lifetime service life.
Article text obtained from the website (MercedesMAN)