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ZF: 9-Speed Limit for Transmission Efficiency
There is no fuel economy gain to be won by adding more than nine forward gears to an automatic transmission, declares ZF Friedrichshafen AG CEO Stefan Sommer.
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There is no fuel economy gain to be won by adding more than nine forward gears to an automatic transmission, declares ZF Friedrichshafen AG CEO Stefan Sommer.
He tells the Automobilwoche Congress in Berlin that the weight and complexity of more ratios would offset any further improvement in powertrain efficiency. Nevertheless, previous media reports say General Motors, Ford and Hyundai are developing 10-speed automatics.
ZF has said that its 8- and upcoming 9-speed gearboxes are 11% and 16% more efficient, respectively, than a conventional 6-speed automatic.
Julio Caspari, who heads ZF's North American unit, told Automotive News earlier this year that a "perfect" transmission would be 11% more efficient than the best gearbox currently in production. But he also inferred that adding more than nine gears may be a marketing rather than performance-driven goal.
ZF began producing an 8-speed automatic three years ago and is scheduled to launch its 9-speed gearbox in 2013. Chrysler Group will use both transmissions in its high-volume models.
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