Lateral thinking: ZF's new nine-cog auto unveiled

German transmission specialist ZF has the production-ready version of its 9HP auto transmission on the starting blocks for an upcoming automotive transmission conference.

Held in ZF's home town of Friedrichshafen, the International VDI Transmissions in Vehicles 2011 Conference will be the setting for the new (production) transmission to be revealed to the public for the first time. ZF claims the new, super-compact box can deliver fuel savings of up to 16 per cent over six-speed units in a similar front/transverse application.

First glimpsed in concept form at the 2009 Frankfurt motor show, the 9HP unit will come in two model lineups covering a torque spread 280 to 480Nm.

ZF attributes much of the 9HP's fuel saving potential to an exceptionally broad ratio spread of 9.84 between low and high gears, and the heights it scales at its top end. By the time it's up in ninth gear, it's running a very long-legged 1900 rpm at 120 km/h – down from 2600 in its six-cog predecessors. Exceptionally close ratios ensure the engine is always in or near its fuel-efficiency sweet spot.

The key to fitting all this into such a small space lies in complex nesting of its four gearsets and six shift elements laterally within the case, rather than placing them in simpler longitudinal fashion. A major side benefit here is that it makes gear-skipping possible, extending its sporting potential and helping cut fuel consumption.

To help maximise its potential through diverse uses, ZF has left the 9HP's operating software and interface electronics open-source, allowing vehicle manufacturers maximum leeway in developing and tweaking it for their own use through future vehicle concepts.

The variability of its shifting points and shifting dynamics gives auto makers and end customers loads of room to move in the way they set the transmission up to divide its priorities between comfort, fuel efficiency and sporting dynamics.

Although it's built to be shoehorned into the relatively small space typical of transverse FWD installations, it's set up for maximum diversity in the ways it can be used. A modular 'construction kit' design allows it to cost-effectively integrate a broad range of starter and hybrid technologies, and to be expanded for AWD application.

For AWD drivetrains, auto makers can add an additional transfer case. In the manner of Volvo and Honda AWDs, the 9HP's AWD Disconnect system decouples the rear axle drive when it's not needed, saving a claimed five per cent over permanent AWD counterparts.

For parallel hybrid drivetrains, manufacturers can order the unit with an electric motor in place of the torque converter. Its design also makes it conducive to auto stop-start systems. The 9HP's design reduces energy-gobbling friction shift elements to just one, helping ensure quick restart response times.

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