The automatic transmission is a system , which shifts gears based on various parameters, the most important of which is the vehicle's speed. One of the main advantages of the AT is the comfortable handling of the car. The automatic transmission ensures a smooth gear change, which the torque converter achieves. The latter consists in transferring the drive torque from the engine to the manual gearbox, one of the elements of the automatic gearbox.
The most popular automatic transmissions are:
- ZF 5HP 24/30 (BMW 5 E39, 7 E38, Z8, Aston Martin DB7, Land Rover Range Rover, Jaguar XJ8, Rolls-Royce Silver Seraph);
- GM 5L40-E (Cadillac CTS, STS , BMW 3 E46, 5 E39, X5 E53, Z3);
- Jeep 545RFE (Jeep Grand Cherokee, Commander, Wrangler, Dodge Dakota, Durango);
- Toyota A340 (Lexus LS , GS, Toyota 4Runner, Supra);
- Toyota A750 (Lexus LX, Toyota Land Cruiser);
- Mercedes 722.4 (Mercedes 190, 200-300 W124);
- Jeep A904 (Jeep Cherokee XJ, Wrangler TJ, Y);
- Mazda/Ford FN4A-EL/4F27E (Ford Transit Connect, Focus, Mazda 3, Mazda 6).
Another characteristic feature of the AT with the classic automatic transmission is that the drive torque over the working fluid is transferred from the engine to the moving wheels. However, one of the main disadvantages of this gearbox is the high fuel consumption.
The functional element of this type of gear is the planetary gear set, which includes:
- Sun gear;
- Ring gear;
- 2 or more planet gears;
- Planet gear carrier.
All planet gears rotate around their axes. This is achieved because the gears are connected to the planetary carrier.
The use of two or more planetary sets in different combinations in the automatic transmission system causes an increase in the number of gears. In modern vehicles, switching takes place via a computer. This, in turn, creates optimal conditions for engine operation, which particularly reduces the possibility of overloading.
However, modern versions with automatic transmission are not equipped with a clutch pedal. The selector lever of the classic automatic transmission therefore only has the following positions: forward, neutral, reverse and park.