Mercedes-Benz has built in excess of 22 million automatic gearboxes since 1961 and has now unveiled its latest automatic gearbox - called the 9G-Tronic - which it claims will set new standards for both fuel efficiency and driving comfort in the premium segment. The nine-speed gearbox will first be fitted to the E 350 BlueTec, which Mercedes-Benz claims is the most fuel-efficient six-cylinder diesel model in its class.
The new gearbox makes use of lightweight materials - the torque converter housing is constructed from aluminium while the transmission housing is made of an even lighter magnesium alloy. Other elements such as the oil pan are now made of plastic to further reduce weight. The 9G-Tronic gearbox may have two additional gears to accommodate, but thanks to the compact design takes up no more space than its predecessor. An advanced lubrication system also means that the 9G-Tronic can incorporate from a start-stop system.
Another innovation in this new gearbox design comes in the form of the minimal amount of planetary gear sets and shift elements. Mercedes-Benz engineers, thanks to some intensive computer-based system analysis, were able to use just four planetary gear sets and six shift elements in total. Three speed sensors continually monitor the operations and provide the transmission control system with the data allowing it to perform more efficient gear shifting, including the ability to skip several gears when accelerating or decelerating.
Thanks to the increased number of gears, the 9G-Tronic allows for reduced levels of noise and vibration inside the car as it allows the engine to operate at lower revs, which also has a positive impact on fuel efficiency. Mercedes-Benz states that, at 120km/h, the E 350 BlueTec's engine operates at just 1,350rpm.
Anything else?
The new 9G-Tronic gearbox will come fitted as standard to the E 350 BlueTec and in time will be added to most of the Mercedes-Benz range thanks to its ability to cope with transferable torque of up to 1,000Nm. It is also designed to be suitable for rear- and all-wheel drive models, as well as hybrid and plug-in hybrid drive systems.