Production of ZF’s eight-speed (8HP) and nine-speed (9HP) automatic transmissions at a facility near Greenville, SC, signals an industry trend to increase the number of gears in passenger vehicles.
“Our intention is not driven by having the highest number of speeds,” Michael Hankel, Member of the Board of Management at ZF Friedrichshafen AG, said in an interview with Automotive Engineering International. "We are working on the highest efficiency for transmissions."
The best configuration, the best ratio spread, and the best combination of gears were key drivers behind the development of the new automatic transmissions, according to Hankel, who oversees ZF’s passenger vehicle powertrain and chassis technologies, as well as electronics systems, for global markets.
“We now have the eight-speed for midsize and larger vehicles and for north-south applications. And we have the nine-speed for east-west (longitudinal) applications,” Hankel said prior to grand opening ceremonies for invited media, politicians, and other guests on July 26.
The newly opened 950,000-ft² (88,000-m²), $385 million plant in Gray Court, SC, is slated to employ 1200 workers in the coming months. By 2016, the facility’s footprint will increase to approximately 1.4 million ft² (130,000 m²) for a total investment of $600 million. When the plant is fully built-out, the workforce is projected to be 1650.
The South Carolina project represents the largest single venture in ZF’s 98-year history. Annual production rates will be 400,000 8HP and 800,000 9HP transmissions. Chrysler and Land Rover have been announced as initial customers for the 9HP. Chrysler is also a customer for the 8HP, which is also manufactured in Saarbrucken, Germany.
As the world’s first nine-speed automatic transmission for passenger vehicles, the 9HP is offered in two model ranges: the 9HP28 (172 lb/78 kg including oil) with up to 147 lb·ft (199 N·m) of torque and the 9HP48 (189.5 lb/85.96 kg including oil) with up to 354 lb·ft (480 N·m) of torque.
Dimensions for the 9HP48—the model that is currently available—are 14.4-in (366 mm) by 16.8-in (427 mm) by 20.5-in (521 mm). The 14.4-in dimension is what allows the nine-speed to be packaged between the engine output and the shock tower.
Gear ratios for the 9HP48 are: 4.70 (1st), 2.84 (2nd), 1.90 (3rd), 1.38 (4th), 1.00 (5th), 0.80 (6th), 0.70 (7th), 0.58 (8th), 0.48 (9th), and -3.80 (reverse).
The 9HP’s 9.81 total gear spread correlates to a 10-16% fuel consumption savings—in comparison to a standard six-speed automatic transmission—when the vehicle is traveling at a constant speed of 75 mph (121 km/h), according to ZF. In the European drive cycle, the acceleration value from 0 to 62 mph (100 km/h) improved by 2 s, with up to 10% lower fuel consumption when compared to a six-speed automatic. The fuel-consumption savings are based on internal simulations verified by independent testing firm TÜV SÜD.
Designed for passenger vehicles with a front-transverse engine, the 9HP is also all-wheel-drive compatible and is start-stop-capable without extra components such as an oil pump.
ZF’s 9HP is the first application of interlocking dog clutches in a passenger car power-shift transmission, the company says. It features a planetary gear set with four simple gear sets and six shift elements, and its use of two interlocking dog clutches—rather than multidisc clutches—equates to a reduction in internal drag losses. In different open/closed combinations, the dog clutches are used for eight to seven and seven to eight; five to four and four to five; and reverse to first and first to reverse. Use of the dog clutches is patented technology from ZF.
The 9HP is also ZF’s first transmission to use an in-house developed ECU.
Although ZF does not develop and produce all of the various electronic parts used for its driveline and chassis products, Hankel pointed out that in-house electronics component production can equate to design integration benefits as well as other advantages.
“After (Japan’s) Fukushima nuclear disaster, we saw bottlenecks where we might be at risk with our customers. Therefore, we think a sound portion of the electronics should be in our own hand. So one of the basic ideas behind this is to control the supply chain to a certain extent by our own activities,” Hankel explained.
ZF engineers have been on a fast track since the nine-speed was shown as a concept study at the Frankfurt Motor Show in 2009. The South Carolina plant’s first shipments of the 8HP and 9HP to customers began in June 2013.
“One of the most important issues of the 8HP and 9HP is the huge progress (shown) in terms of fuel efficiency and CO2 emission reduction,” said Hankel, who recently wrapped a five-year stint as CEO of the steering systems joint venture with Bosch, ZF Lenksysteme GmbH.