BMW equips its 2010 and 2011 upper echelon Series 5, 6 and 7, and M sport models with six- or eight-speed automatic, or the sport Steptronic, transmission. BMW engineered each transmission to save fuel but provide exceptional acceleration on the road.
Six-Speed
BMW equips its V-8 and V-12 models with a ZF Friedrichshafen, six-speed automatic with the sixth gear achieving low revolutions while the vehicle is moving at high speeds to increase fuel-efficiency and save wear and tear on the engine. Its gear ratios are a first gear 4.17-to-1, second 2.34-to-1, third 1.00-to-1, fourth 1.14-to-1, fifth 0.87-to-1 and sixth 0.69-to-1, according to BMW.
Steptronic
The six-speed, Steptronic sport automatic is found on high-performance BMWs, such as the Z4 Roadster. It features two structures that allow the transmission to shift from one to the other to provide continuous and uninterrupted power to the wheels from the engine. The driver uses a shift lever or steering wheel paddles to shift. The Steptronic's gear ratios are 4.17-to-1, 2.34-to-1, 1.52-to-1, 1.14-to-1, 0.87-to-1 and 0.69-to-1.
Eight-Speed
The ZF eight-speed automatic provides more fuel and overall performance efficiency than the six-speed version and still maintains a smooth shift between gears. Fuel efficiency is increased by 11 percent. Its gear ratios are 4.71-to-1, 3.14-to-1, 2.11-to-1, 1.67-to-1, 1.29-to-1, 1.00-to-1, 0.84-to-1 and 0.67-to-1.
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