The World’s First 9-Speed Automatic Passenger Car Transmission

Economy with increased performance – ZF once again shows the automotive world that these two attributes aren’t mutually exclusive.

ZF is the first transmission manufacturer worldwide to develop a modern passenger car automatic transmission with 9 gears. It has been designed for vehicles with transverse engines and front or four-wheel drive and can thus be installed in 75 percent of all cars produced worldwide. This means that the transmission not only replaces the current longitudinally installed 8-speed automatic transmission, but it also represents an independent design for a transverse installation position. The concept study of this front-transverse transmission caught the industry's attention already at the IAA 2009.

Sporty and fuel-smart


Compared to today's standard 6-speed automatic transmissions for front-transverse motors, ZF's new 9-speed automatic transmission clearly improves both driving performance and fuel economy.
This combines a new ZF production highlight with reaction and shifting times so short that they are almost beyond perception. It makes double- and multiple-gear shifting a reality. Thus, the new transmission system is equipped with the same 'sporty genes' as already its 8-speed automatic transmission predecessors; in conjunction with the excellent shift comfort characteristics, they certainly entail ultimate customer satisfaction.

Transmission control 9HP



Due to reasons of cost efficiency and installation space optimization, ZF engineers did not use a fully-integrated mechatronics module for all sensors, actuators, and the electronic control unit (ECU) in the 9 HP. Instead, the ECU is installed separately from the now significantly smaller hydraulic control unit (HCU), namely on the upper side of the transmission housing. The sensors can be found inside the transmission, vehicle-side signals are connected directly to the male plug of the ECU.
In case of the 9HP, ZF develops and produces the complete ECU itself for the first time. A powerful embedded flash controller can realize complex control algorithms. Its calculation performance is comparable to the controller used in the 8-speed automatic transmission and can be increased by approx. 30 percent on demand. Thus, the 9HP will also be equipped for even more comprehensive software functions in the future. The layout of the ECU printed circuit board has been designed so that the different hardware requirements of the OEMs can be met without any problems.
As a construction kit, the ECU is suitable both for a pure shift-by-wire actuation (electronic shift system) and for a shift-by-wire/park-by-cable actuation (electronic/manual shift system):

Fuel consumption and driving performance of the 9HP28 in comparison to competitors.


In addition to the design improvements mentioned at the beginning, the consumption-optimized driving strategy of the 9HP also contributes decisively to reducing fuel consumption. In total, the 9HP in the front-transverse sector realized consumption savings that were not thought possible: Compared to the 6-speed transmissions of the first generation, the 9HP saves up to 16 percent fuel.
The 9HP technology moves on eye level with the double clutch technology with respect to fuel consumption, and shows significant advantages with starting acceleration, which can be improved by >2 seconds in comparison to 6-speed automatic transmissions.

In order to be successful on the market, however, it is equally important to provide comfort and an attractive driving performance for the end customer. What is also worth mentioning here is the speed reduction in the highest gear: It serves significantly better acoustics in the vehicle and increases driving comfort. ZF has designed all control components for shorter response and shift times in order to increase the performance. Direct multiple gearshifts further increase driving dynamics. In this process, shift points and shift dynamics can vary from an emphasis on comfort to very sporty which makes it possible to affect the performance of the vehicle according to the driver's wishes. Thus, the 9HP meets all requirements in terms of function and flexibility of modern automatic transmissions and shows the potential they also bear for front-transverse vehicles regarding their sportiness.