While a six-speed manual is considered ample for any occasion, automatic transmissions are sprouting extra cogs like new spots on a child with chickenpox. The seven-speed auto seemed excessive and the eight-speed almost redundant, and yet the ZF 8HP, as use by several manufacturers including BMW and Jaguar Land Rover has proved that any concerns about constant hunting for gears or slow kick-down response were unfounded.
Buoyed by the successful applications, Land Rover has announced it will demonstrate the world's first nine-speed automatic at the 2013 Geneva Auto Show.
The ZF 9HP transmission, a first for a passenger car, has been designed for transverse applications. With Land Rover as the lead partner with ZF on the project, the aim is to reduce emissions and improve efficiency.
The smaller step between each ratio should help with response times during acceleration, and improved refinement by virtue of smoother shifting and lower engine speeds when cruising.
It's claimed that first gear in the 9HP is lower than the existing six-speed transmission. What's more, it's designed for off-road, towing and on-road use so has been built robust to ensure all-terrain ability.
Another detail is that the existing six-speed auto transmission downshifts sequentially, whereas the 9HP is able to "skip-shift" for faster downshifts to match rapid deceleration.
The torque converter houses a multi-stage damper for smoother departure and improved refinement. It also boasts adaptive shifting to interpret the driver's inputs.
Despite the extra three gears, the 9HP is only 0.24" (6mm) longer and actually weighs 16.5 lb (7.5kg) less than the outgoing six-speed transmission.
The new nine-speed transmission will be produced at ZF's facility in South Carolina, USA.