According to ZF Friedrichshafen CEO Stefan Sommer, nine gears in a transmission is the “natural limit,” and should be the magic number to end the race to add more gears.
Efficiency gains in automatic transmissions have gone from an arguably secondary concern a few years ago to one of the foremost weapons in the fuel efficiency battle. It wasn’t long ago that four- and five-speed automatics ruled the roost, but with purse strings tightening, regulators and customers alike are demanding better fuel economy.
“There is no hard line, but you have to consider the law of diminishing returns. The question is whether adding even more gears makes sense,” Sommer told Automobilwoche. Going beyond nine gears adds more weight and technical complexity to the transmission, which will detract more fuel efficiency than it gains.
Julio Caspari, head of ZF in North America has said in the past that the race to add more gears is more a demand from marketing, rather than actual efficiency gains, as the most efficient transmission today is only 11 percent from being a “theoretically perfect transmission.”
[Source: Automotive News Europe]