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It used to be two or three gear ratios in an automatic gearbox was the norm. It’s now up to nine.
Land Rover will soon ship its Evoque CUV with a new nine-speed automatic transmission designed by driveline specialist ZF.
The British company said increasing the number of gear ratios to nine will help reduce emissions and improve efficiency
Land Rover will demonstrate this world’s first nine-speed automatic transmission for a passenger car at the 2013 Geneva Motor Show.
Known as the ZF 9HP, this transmission is designed for transverse applications, and is said by Land Rover to be one of the most efficient and technically advanced transmissions ever used in a production vehicle.
Increasing the number of gear ratios from six to nine will help reduce emissions and improve efficiency. Smaller ratio steps also give improved response during acceleration, with improved shift quality and refinement. A higher top gear improves efficiency by lowering engine speed, which also improves comfort and reduces noise when cruising at highway speeds.
The lowest ratio in the 9HP is lower than the existing six-speed transmission and is designed for off-road use, towing, and on-road conditions like steep gradients.
Whereas the existing six-speed transmission makes downshifts sequentially, the 9HP has a skip-shift function for much swifter downshifting to meet rapid deceleration demands. If the driver requests a downshift when the vehicle is traveling too fast for the selected gear, the transmission will remember the request and make the shift when the speed drops to an appropriate level. “Fast-Off” mode measures the rate of throttle release, anticipates further requests by the driver for high power, then holds the gear if necessary.
The torque converter incorporates a multi-stage damper system for smoother pull away and improved refinement. An innovative adaptive shifting system matches the driver’s mood within seconds, sharpening up during brisk driving and then seamlessly shifting to a more economical program when taking a more relaxed driving approach. Additionally, “Curve Mode,” detected acceleration/deceleration forces, and pedal position all control upshift timing.
Despite the extra three gear ratios, the 9HP is only 0.24 inches (6mm) longer and actually weighs 16.5 pounds (7.5kg) less than the outgoing Evoque six-speed transmission. The compact packaging is achieved by using a number of innovative design features: a new compact hydraulic vane-type pump; two patented dog clutches replacing bulkier conventional clutch packs; and a nested gear set.
ZF said this transmission can return savings of up to 16 percent in fuel consumption when compared to a six speed transmission; Land Rover has not yet revealed the official fuel consumption ratings of the Evoque with this new nine speed transmission.
The new nine-speed transmission will be produced at ZF’s Gray Court facility in South Carolina, USA.
The following is a promotional video produced by ZF that illustrates some of the internals of the 9HP transmission:
We can expect this transmission to show up as part of the driveline of other vehicles in the near future. ZF said the 9HP is compatible with hybrid technology and with start-stop features.