More gears in a transmission does two things, smooths out shifting during acceleration and increases fuel economy, which is sorely needed in tomorrow’s automobiles.
Since 2002, Ford Motor Company and General Motors have partnered to develop and manufacture six-speed automatic transaxles for their front-wheel drive vehicles. Some eight million vehicles have been sold with the co-developed transaxle under both Ford and GM hoods.
While the two companies have trailed behind other automakers in offering transmissions with more gearing, their continued partnership is now leading into new territory to develop nine- and ten-speed automatic transmissions for the next generation of vehicles.
The basic function of the transmission is to convert the motion of a conventional engine to a lower speed, and higher torque, to power the wheels and move the vehicle forward. The number of gears is important because it determines how hard the engine has to work to accelerate or cruise on the highway.
When the engine works too hard because the gear ratio from one gear to the next is too different, fuel is being wasted. On acceleration adding more gear ratios allows the engine to work in its most efficient range, maximizing fuel economy.
According to research firm LMC Automotive, more than 33% of vehicles built in the US will have at least an eight-speed transmission, but that transmissions with more than ten speeds will probably not be developed because of the complexity of such a system. [Semi-trucks have up to eighteen speeds, but require special training and a lot of room under the cab.]