ABD - AUTOMATIC BRAKE DIFFERENTIAL - Differential lock with standard disc brakes

ABD - Automatic brake differential or in German Automatisches Bremsdifferential, is an automatic lock (lock) of the differential of the drive wheels, which has a blocking effect not directly by self-braking bevel gears, but indirectly, by alternately activating the brakes on the side where the wheels slip. In this way, the driving torque equal to the braking torque on the opposite side is transmitted to the opposite wheel, in contact with the ground (the brake acts like a rotating support).

ABD significantly improves the driving properties on slippery surfaces, because the car is not left without drive, and stability in the curve. Construction is much simpler than the classic mechanical or 'hybrid' with viscous couplings in the function of blocking. However, in extreme driving, the brakes can overheat, as they take over the functions of closing the differential and braking at the same time. BMW uses the term EBS (Electronic Differentials). Pictured below is a classic differential, a differential with a mechanical shutter, and a differential with viscous coupling locks.

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