How 85 billion gearset concepts led to a nine-speed revolution

History · Published 9 October 2026 Swipe more like this →

In short: To design the 9G-Tronic, engineers examined 85 billion gearset concepts. The goal was to increase efficiency without adding weight or space. The result is a patented, highly integrated system that uses a complex mix of parallel and serial power flows to achieve unprecedented gear distribution.

The Mercedes-Benz 9G-Tronic, internally known as NAG 3, represents the third generation of the company's modern automatic transmissions. Developed at the Stuttgart-Untertuerkheim headquarters, it was designed to succeed both the 5G-Tronic and 7G-Tronic models. To achieve its nine speeds without increasing manufacturing complexity, engineers moved away from purely serial power flows, instead utilizing a patented concept that combines parallel and serial epicyclic gearing.

Efficiency was a primary driver for this development. By utilizing a wider gear span to allow for 'downspeeding'—lowering the engine speed level—the transmission can reduce fuel consumption by 6.5%. This design also improves noise-vibration-harshness comfort, reducing exterior noise by up to 4 dB(A). For example, in a 2013 Mercedes-Benz E 350 BlueTEC, 120 km/h is reached in 9th gear at an engine speed of approximately 1350 rpm.

The 9G-Tronic is highly integrated, which has implications for maintenance. Components like the oil filters in the plastic oil pan and the mechatronic module—which houses the sensors, control unit, and electrohydraulic shift plate—are designed to be replaced as entire assemblies rather than individual parts. Despite this complexity, the unit is 1 kg lighter than its predecessor and occupies the same installation space. While it offers superior gear distribution compared to 10-speed transmissions from Ford/GM or Aisin/Toyota, some critics note the relatively small steps between the 5th and 6th, and 6th and 7th gears.

The technology has branched into specialized versions. The MCT 9G, used in the Mercedes-AMG E 63 4Matic+, replaces the torque converter with a wet clutch to optimize accelerator response and weight. Meanwhile, the Jatco 9AT version is licensed for use in Nissan and Infiniti vehicles, featuring a limited input torque of 700 N⋅m.

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