Pic. 6.9. Compact five-speed automatic transmission in the context: 1 - torque converter; 2 - multi-plate clutch; 3 - planetary mechanism; 4 - locking gear of the parking mode; 5 - flange of the cardan shaft; 6 - intermediate lever controlled by the gear selector on the center console
For the five forward gears in the new generation automatic transmission, only three planetary gears are used 3 (pic. 6.9) and six elements of multi-plate clutch 2 to transmit torque without interrupting the flow of power. Until now, the same number of gears required four planetary gears and seven clutch elements.
Instead of the multi-plate clutches used for these purposes (clutches) and band brakes, Mercedes engineers used multi-disc clutches and multi-disc brakes in the new generation of automatic transmissions. The advantage is that during the entire service life of the unit, the quality of their work remains optimal. Reducing the number of planetary mechanisms made it possible to make the automatic transmission more compact: neither five-speed automatic transmissions of this class from other manufacturers, nor four-speed automatic transmissions can even come close to the Mercedes automatic transmission in this parameter. Its length is only 600 mm, which is 150 mm shorter than other comparable automatic transmissions. Mercedes' four-speed automatic transmission is about the same size, but it has one gear less and lacks a lock-up clutch torque converter. The new automatic transmission differs in terms of mass. Its weight, equal to 80 kg, is almost a third less than its analogues. This result was achieved thanks to the use of sheet metal in the production of the Mercedes automatic transmission case instead of heavy cast and forged structures.
Pic. 6.10. The disassembled five-speed automatic transmission clearly demonstrates a noticeable reduction in the number of parts compared to previous samples
Thanks to a modern design, the new automatic transmission consists of only 630 parts (fig 6.10). This is 45% less than comparable five-speed models.