The first nine-speed automatic transmission with torque converter, the 9G-Tronic, has made its world debut in the Mercedes-Benz E 350 BlueTEC.Set to become one of the most fuel-efficient six-cylinder diesel models in its class, NEDC fuel consumption in the E-Class is reduced to 5.3 liters of diesel per 100km. The 255ps V6 diesel engine emits CO2 emissions of 138g/km. As a result, the new models undercut their predecessors in terms of both consumption and CO2 emissions. The higher number of gears and the broader gear ratio spread also help to increase drive comfort and enhance the conversion of engine power into traction.
The reduced fuel consumption has primarily been achieved as a result of the high level of efficiency of the transmission. As part of this, the broad ratio spread of 9.15 for gears one to nine enables a reduction in engine speed and is a decisive factor behind the high level of energy efficiency and ride comfort.
Despite two additional gears and a maximum transferable torque of up to 1,000Nm, the new automatic transmission requires as little installation space as its predecessor and, in addition, is lighter. The two-piece housing design has been retained: the torque converter housing is made of lightweight aluminum, while the transmission housing with weight-optimized plastic oil pan is made of a lighter magnesium alloy.
The nine gears have been implemented with four planetary gear sets and six shift elements. Three speed sensors monitor operation and provide the transmission control system with corresponding data for effective shifting. Here it is possible for several gears to be jumped when accelerating or decelerating.
The new automatic transmission is fitted with two pumps to ensure the supply of 2nd-generation synthetic fuel economy engine oil. The smaller mechanical main pump, featuring an off-axis design, is located next to the main shaft and is chain-driven and fed by a separate electric auxiliary pump. This design enables the flow of lubrication and coolant to be controlled actively on demand and also means that the 9G-Tronic can benefit from a start/stop system. Hydraulic efficiency has also been increased as a result of the addition of a direct control system.
The 9G-Tronic is suitable for rear-wheel and all-wheel drives as well as hybrid and plug-in hybrid drive systems and will be used in almost all model series and engines in the coming years. The market launch will take place in September 2013.
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