The Audi Quattro has another additional differential, the so-called middle or intermediate, located between the front and rear axles and designed to equalize the difference in rotation speed of the front and rear wheels.
Differential locks are activated at the moment when, for example, a wheel on one axle begins to turn on a slippery section of the road while the other wheels are on a hard surface and do not slip.
An undesirable difference in the rotation speed of the wheels of the two axles occurs. To prevent and equalize this difference, an additional automatic differential lock is designed, which in the current road situation automatically locks the slipping wheel, and transfers the driving force to the other axle, where there is good traction of the wheels with the road.
The rear axle differential lock operates on a similar principle.
This blocker is primarily designed for smooth starting and acceleration of the car.
Rear axle differential lock engagement procedure
The differential lock is activated by pressing the "DIFF" button on the center console next to the parking brake lever. It can be engaged or disengaged both before starting to move and while driving at speeds of up to 25 km/h.
Pressing the button only turns on the device. The lock is activated only under appropriate conditions, when there is a large difference in the rotation speed of the rear wheels. As soon as the vehicle speed exceeds 25 km/h, the lock is automatically turned off.
At the same time, remember that when the vehicle speed drops below these values, the system does not turn on automatically.
The operation of the differential lock is monitored by a control lamp located on the panel in front of the "DIFF" key. It lights up when the locking device is actually engaged.
At the same time, the "ABS" control lamp lights up, since when the differential lock is activated, the "ABS" anti-lock braking system is switched off. After the lock is switched off, the lamp goes out. If this control lamp does not light up when the locking device is switched on, check the serviceability of the electrical equipment.
(Read the original source on the website: audimanual)