The boss of transmission company ZF Friedrichshafen believes that the numbers are not with shifters that offer any more than nine speeds.
Speaking with German paper Automobilwoche, Sommer said that reaching beyond nine speeds adds unnecessary weight and complexity without any decent gain in fuel efficiency.
"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," he said.
Julio Caspari, head of ZF in North America, has also hinted that the race to add gears may be driven more by marketing and a perception among buyers that "more is better".
Caspari told industry paper Automotive News that, in terms of efficiency, ZF's current eight-speed transmissions are separated from "theoretical perfection" by a margin of just 11 percent.
Chrysler is also expected to manufacture the new 9HP transmission under license in the US for its new front-wheel-drive models.
ZF says the 9HP auto will handle between 270 and 480Nm of torque, while bringing fuel consumption improvements of up to 16 percent over the more common six-speed option.
According to ZF, its current eight-speed transmission, introduced in 2009, offers an 11 percent improvement over a standard six-speed auto.