Mercedes-Benz is one of the few automakers in the world that can produce automatic transmissions in-house. Mercedes-Benz has been developing its own automatic transmissions for more than 50 years. In the 1990s, when 3AT became a street product and 4AT was still high-end, Mercedes-Benz began to work on the research and development of 5AT.
The 5G-Tronic is also equipped with a torque converter and an electronically controlled lock-up clutch. The lock-up clutch creates a virtual rigid connection between the engine and transmission input shaft to lock up in high gears, preventing slippage between the impeller and turbine, reducing power loss, and improving transfer efficiency in a wide range of operating conditions. The use of a large number of electronic control components makes the 5G-Tronic shift more freely, with better fuel economy, longer service life, and higher reliability.
After 2000, 4AT was the mainstream among the models on the market at that time, and 6AT was still very "tall", and only very few models would be equipped. Although 5G-Tronic is still a high-end product, in the fall of 2003, the world's first 7AT gearbox was born. The 7G-Tronic is a vertical 7-speed manual transmission with a maximum torque of 735Nm, matching V6 and V8 gasoline and common rail diesel engines, and is suitable for rear-wheel drive and four-wheel drive models. Once the dual clutch actuator was launched, it quickly replaced the 5-speed automatic transmission that was equipped at that time, and was assembled on its rear-wheel-drive platform models.
In addition to adding 2 forward gears to the gear, the 7G Tronic dual clutch also has 2 reverse gears, and the fastest reverse speed can reach 80km/h. In addition to increasing the range of transmission ratios, the difference between the various transmission ratios is also closer than that of the 5-speed automatic transmission. In addition to the relatively large deceleration in the first 2 gears, which is conducive to starting and increasing the speed, the connection from the 3rd gear has gradually become closer, especially after the 5th gear (overspeed gear), the drop ratio is extremely small, which is relatively better at high speeds. Smoother thrust, but also fuel economy and comfort.
Unlike traditional automatic transmission clutch actuator that can only be engaged in high gears, in the 7G Tronic dual clutch, the lock-up clutch can be engaged from the first gear, which can further reduce power loss and improve transmission efficiency. For added comfort, the torque converter lock-up clutch features slip control for extremely smooth engagement, minimizing possible shock during shifts.
In 2010, Mercedes-Benz carried out a comprehensive renovation of the 7G Tronic dual clutch, and the upgraded 7AT was named 7G-Tronic Plus (enhanced version). 7G-Tronic Plus has updated the torque converter, added a torsional vibration damper and an electronically controlled lock-up clutch, and replaced a brand-new transmission oil, which makes the vehicle shift more quickly and comfortably. Transmission efficiency has increased by 31%.
In 2010, as competitors successively launched models with 8AT, Mercedes-Benz, which has been leading the development of automotive technology, issued a rhetoric such as "We are developing a 9AT gearbox!" In 2013, after a lapse of three years, Mercedes-Benz fulfilled its promise three years ago. The newly developed 9G-Tronic, code-named 725, won the title of the world's first longitudinally mounted 9AT gearbox, once again becoming the target of other car manufacturers and also China spare parts manufacturer.
Due to the tighter gear ratio, the power connection between gears is more compact, especially in low gears, the 1st to 3rd gears are smoother than the previous 7G Tronic dual clutch. The maximum input torque that can be tolerated can reach 1000 Nm. Even if it is matched with a large-displacement engine, there is no problem at all. Such an indicator is enough to meet most of Mercedes-Benz's models, even AMG's performance version models, which is far from the maximum. A 9-speed front-wheel-drive platform automatic transmission with a torque of only 480 Nm can match!