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Automatic transmission In Audi A4 two various models of an automatic transmission are used for installation: first, developed VW a transmission «AG-4» for the four-cylinder engine without a turbo-supercharging, secondly, designed ZF a transmission «5 HP 18» for the six-cylinder engine. As it is already clear on a designation, it is a question in one case of a four-speed transmission, in other case – about five-step. Both transmissions cope in the elektronno-hydraulic way, and this management works depending on various entrance parametres (number of turns of the engine, speed of movement, loading and so forth) when the following transfer joins. Besides, management distinguishes a manner of driving of the driver and establishes points of a gear change from "sports" to "economic", thus it is not necessary to put in action any switch. All the system as a whole is called DSP – Dynamische Schalt-Programm (the dynamic program of a gear change). Besides, at a transfer choice the lay of land is considered – i.e. Automatics chooses a mode of the gear change different from movement on mountain road on equal road. Main principles of functioning The basic link of all automatic transmissions are so-called planetary complete sets. They consist of a gear wheel round which three other gear wheels rotate. From above the ring with an internal teeth is put on. Each pair from these elements is connected in a set of gear gear wheels and forms an own small two-speed transmission. In these transmissions the way of their switching is ingenious. Transfer switching is carried out at the expense of keeping or liberation of details of the planetary complete set. It becomes without interruption of a stream of force. Keeping and liberation provide lamellar couplings and lamellar brakes with a hydraulic drive. For reception of a multistage transmission two planetary complete sets are consistently connected. At a correct arrangement of transfers it is formed four- or a five-speed transmission with backing transfer. Coordination of work of complete sets of gear wheels is provided with transmission management.