9G TRONIC automatic transmission

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9G-TRONIC is the world's first nine-speed automatic transmission in the premium segment to feature a hydrodynamic torque converter. With nine forward gears, this automatic transmission combines dynamics, efficiency and comfort at an entirely new level.

It impresses with swifter and smoother gearshifting actions. At the same time, it contributes towards reducing fuel consumption. The wider gear spread allows a reduction in engine speed. This results in enhanced ride comfort and a reduction in the noise level.

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More efficient, more comfortable, more dynamic.

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The further improved torque converter which was already in use on the 7G-TRONIC PLUS makes use of double turbine torsion damper and centrifugal pendulum technologies to sustainably lower the torsional vibrations in the drivetrain. This makes for comfortable driving with low engine speeds even in higher gears, whilst also lowering the fuel consumption.

Optimisations in all areas – from the transmission components, the automatic transmission oil and the lowering of the working pressure, right up to the implementation of a modified piece of software – extend the life expectancy and maintenance intervals, while also improving comfort and raising efficiency.

Despite having two additional gears, the 9G-TRONIC transmission is just as compact as the 7G-TRONIC PLUS and is even one kilogramme lighter. The converter housing is made of an aluminium alloy, while the transmission housing is made out of an even lighter magnesium alloy with a weight-optimised plastic oil sump.

The nine gears are achieved with only four simple planetary gear sets and six shift elements. Three speed sensors monitor the functioning, and supply the transmission control with the necessary data for highly effective gearshifting. Two pumps ensure a reliable and energy-efficient supply of long-lasting, shear-resistant second-generation Fuel Economy low-friction oil to the transmission. The mechanical main pump has been drastically reduced in size, is driven by a chain and is supplemented by a separate electrical auxiliary pump. This design allows needs-based active regulation of the lubricating and cooling volume, whilst also making it possible to equip the 9G-TRONIC transmission with a Start/Stop system.

All components for the shifting, lubricating and control processes are fully integrated in the transmission housing and thus improve the control quality and reliability of the 9G-TRONIC.

Direct coupling of electrical actuators to the appropriate hydraulic slide valves makes changing gear quicker and more comfortable. The control unit integrated in the vehicle's electronics architecture analyses the input signals of the transmission as well as requests from other control units; this data then allows the system to control gearshifting in the best possible way.

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