ZF announces world’s first nine-speed auto

GERMAN gearbox giant ZF has unveiled details of the world’s first nine-speed automatic transmission, claiming fuel economy benefits of up to 16 per cent while offering shift times “below the threshold of perception”.

The news comes soon after announcements from Ford and General Motors announced that they are each developing their own eight-speed automatics in-house.

The ZF ‘9HP’ transmission is intended for transverse front-wheel drive applications and has been developed to be compatible with idle-stop systems. In addition, its torque converter can be replaced by an electric motor for use in hybrid drivetrains.

It can also be fitted with a transfer case that adds all-wheel drive capability designed to keep the rear wheels isolated from the transmission unless extra traction is required – thereby reducing frictional losses and offering a five per cent fuel saving compared with permanent all-wheel drive.

ZF says the 9HP’s design, and powerful programmable and updatable electronic brain with “open software and interface structure”, makes the transmission flexible enough to be used in a broad range of vehicle types.

Like the widely acclaimed ZF eight-speed auto used in many German luxury cars, the 9HP can make multiple shifts when required, for example changing straight from third to fifth.

The transmission can prioritise comfort and smoothness, maximum fuel economy or become, as ZF puts it, “extremely sporty”.

Software can be used to tailor the character of the transmission and suit the type of car it is fitted to – or where offered with driver-configurable settings – as well as the driver’s mood and driving style.

ZF announced two variants of the transmission will be available, for engines with torque outputs from 280 Newton metres and capable of withstanding up to 480Nm.

Timing of the transmission’s debut in a production vehicle is yet to be announced.

Having nine gear ratios enables very low first and second gears for quick acceleration and an extra-tall top gear for cruising at low engine revs to save fuel. ZF claims that only 1900rpm is required cruising at 120km/h compared with 2600rpm for an equivalent vehicle with a six-speed transmission.

The 9HP’s small gear steps also give the engine a better chance of running in its fuel consumption sweet spot for any given road speed.

Chrysler – which a year ago announced plans to build a ZF eight-speed automatic in the US under license from 2013 – and Mazda have both mentioned plans to integrate nine-speed transmissions into future models while BMW has considered – and rejected – 10-speed transmissions.

ZF’s latest development shows how far automatic gearbox technology has come in recent years. In 2006 Lexus debuted the world’s first production eight-speed automatic – by adding an extra two ratios to an existing six-speed unit – in its LS430 limousine, outdoing the seven-speed ‘7G-Tronic’ unit that had been fitted to high-end Mercedes-Benz models since 2003.

In 2008 the first seven-speed dual-clutch automatic transmissions emerged from BMW’s M division and Volkswagen Group.

Traditional objections to autos – even in manual-obsessed Europe – are being addressed by the new wave of transmissions, which offer greater driver interactivity through steering-column mounted paddles and are increasingly able to provide greater fuel efficiency over their manual counterparts.

According to ZF, the proportion of automatic transmission-equipped cars in Germany has risen from 15 per cent in 2000 to 28 per cent in 2010, a trend reflected across Western Europe.

ZF predicts that Western European sales of vehicles fitted with dual-clutch transmissions will have risen 1200 per cent in the decade to 2016.