In the picture below, you can see a seven-speed double-clutch gearbox, this however, is not really our subject. Apart from the fact, that it can handle a great amount of torque, because in the AMG-version, it is powered by (according to Daimler) the strongest four-cylinder which is a 2-liter and produces 265 kW (360 HP). Indeed, this is also not our subject, except for the fact that an engine like this could of course, overtax the front-wheel drive.
Why then is the double-clutch gearbox the first part of the all-wheel drive that can be seen? Because this all-wheel drive, derived from the transverse-mounted front-wheel drive, can only be had from Mercedes with this gearbox. One reason could well be, that Mercedes only fitted this drive-train with an additional rear-wheel drive relatively late. An advantage is however: It is solidly integrated into the gearbox, thus relatively slender.
If up front, the torque is transferred to the cardan shaft, the control unit must be integrated into the final drive of the rear axle. In a front-wheel drive, this takes a bit of the pressure off the front axle. Before we go on to the regulation, we would like to mention, that some drive shafts, like this one here, have at least one universal joint, so that in the event of an accident, they can more easily fold out of the way.
This now, is the multiple-clutch, which runs in oil, shortly before the rear axle. If you stop the above pictures at number 3, you can recognise the hydraulic pump behind the small group of discs. This has a certain resemblance to the first Haldex constructions. Only that this pump builds up the pressure after only a few degrees of angle and can thus, assign the torque to the rear axle variably. 06/15