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ZF goes straight to eight
Not to be outdone by Lexus, ZF reveals an all-new eight-speed automatic transmission
4 May 2007
GERMAN driveline and chassis component supplier ZF Friedrichshafen AG, better known simply as ZF, has revealed an all-new eight-speed automatic transmission.
Presented to 1000 engineers at last week's 28th annual International Vienna Motor Symposium, the brand-new self-shifting gearbox is claimed to realise fuel consumption savings of up to six per cent, compared with the second-generation six-speed transmission it has supplied to BMW, Audi, Jaguar, Land Rover, Volvo and Ford Australia since 2006.
The latest ZF auto features four planetary gear sets, five shift elements and, in terms of gear ratios, betters both the current ZF six-speed auto it will replace as well as Mercedes-Benz's own seven-speed 7G-Tronic auto.
Not to be outdone by Toyota, it also matches the world-first eight-speed automatic transmission that was launched in the new Lexus LS460 this month.
Along with reduced fuel consumption, ZF says its eight-speeder also reduces power losses and requires the same installation space as its predecessor.
"Our main development target was to find a transmission concept which allows for significant additional fuel consumption reduction and thus offers tangible added value to our customers and drivers without making any compromises in terms of performance," said ZF's executive vice-president, technology and group executive of the car driveline technology division, Dr Michael Paul.
"The number of gears was not given top priority." ZF claims the new auto is up to 14 per cent more fuel-economic than a traditional five-speed auto, thanks largely to the employment of four planetary gear sets and five shift elements, only two of which are opened in each gear to "considerably lower drag losses".
Also helping to lower fuel consumption and CO2 emissions is a higher total ratio and the use of "modern torsional vibration damping systems" in the torque converter, while the new ZF also comprises a small vane cell pump mounted parallel to the axle.
The new auto's power-to-weight ratio is also higher because it can transmit a higher input torque at the same weight, compared to the ZF6. However, ZF says that in terms of shift comfort, response and speed, the ZF8 "operates at the already very high level of the second generation of the automatic six-speed transmission".
ZF says its modular design will again suit a wide variety of vehicle applications, including all-wheel drive and hybrid powertrains.
"The automatic eight-speed transmission offers the possibility of implementing both a micro hybrid with a crankshaft starter generator and a full hybrid in the form of a parallel hybrid," says ZF. "All known hybrid functions can thus be implemented in combination with the new automatic eight-speed transmission." While there's no word on exactly when the ZF8 goes into production, expect the future generations of a wide variety of models to employ it, including Ford's Falcon and Territory, BMW's 1/3/5/7/8/X and Z Series, Jaguar's S-Type, XJ and XK, Land Rover's Range Rover Vogue and Sport, Audi's A4/A5/A6/A8 and Q5/Q7, and Volvo's S80/XC90.
ZF, which employs 55,000 workers at 120 facilities in 25 nations, says its invests five per cent of its annual sales (which in 2006 amounted to $993 million from a staggering total of $19.4 billion) in research and development.
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