Earlier this year, it was announced that German transmission supplier ZF would develop the world’s first nine-speed automatic transmission for use in passenger cars. The company has recently released more info on that project, shedding light on the new transmission’s fuel economy benefits, its proposed applications and, of course, how it works.
Exhibiting at the International VDI conference, ZF announced that its nine-speed transmission achieves fuel savings of 16 percent over conventional six-speed autos used today. The nine speeds of ZF’s new transmission, called the 9HP, are made possible by four separate gear sets and six shifting elements. ZF claims that fitting these components inside a single transmission casing was a challenge, especially given the space restrictions of a front-transverse engine – the layout this transmission was designed for.
Using complex workarounds, the driveline experts were able to pull it off, resulting in a transmission with smaller gear steps that allows the engine to always run in its optimal speed range for best efficiency – 1900 rpm at 120 km/h (roughly 75 mph) as opposed to 2600 rpm in modern six-speed autos. In addition to aiding fuel economy, ZF claims the 9HP also improves comfort and driving dynamics.
On top of front-wheel-drive cars with transverse engine layouts, ZF also claims multiple applications for the 9HP, citing all-wheel-drive cars and hybrids as prime candidates. To better facilitate the adoption of its transmission in as many cars as possible, ZF has “construction kits” available that can adapt it to other applications. These options make it easier for manufacturers to incorporate the nine-speed transmission into their cars, with features like an additional transfer case for all-wheel-drive cars that can be decoupled to save fuel. Since the 9HP is already start-stop-capable, ZF claims that it is easy to hybridize, requiring only an electric motor in place of the torque converter.
Although no mention was made about possible customers for the 9HP, as we reported earlier, Chrysler has expressed interest in a nine-speed transmission for some time now. Since ZF is expected to supply the company with longitudinal eight-speed units, it only makes sense that Chrysler would turn to ZF when it wants an additional gear for its next transmission.