Hyundai launches its first proprietary 6-speed automatic

  • 14-Dec-2009 04:17 EST
Hyundai 6-speed auto trans.jpg
More than 600 parts comprise Hyundai's all-new, six-speed automatic transmission. The transmission's design and development involved 150 engineers working nearly four years on the project. The "super-flat" torque converter is supplied by Exedy Corp.

Hyundai doesn't need a license for its newest transmission as the six-speed automatic's 300 patentable items underscore a new direction for the automaker.

"This transmission is our first internally designed six-speed automatic. In the past, the company has licensed designs from others, but this six-speed automatic is a proprietary design," John Juriga, Hyundai-Kia America Technical Center's Director of Powertrain, said in an AEI interview recently at the Ann Arbor, MI, facility.

Although not the first six-speed automatic transmission used in a Hyundai vehicle—the Genesis offers a ZF-sourced six-speed—the new unit plays a key role in helping the automaker achieve a product milestone. The 2011 Sonata is expected to offer a claimed best-in-segment 35-mpg highway fuel economy rating, which Juriga said is due in part to the new transmission's 2.885:1 final drive ratio.  

There will be five variants of the new six-speed, known internally as the A6MF2. Its torque capacity and 5.45 total ratio spread are designed to accommodate a variety of gasoline and diesel engines, according to Juriga.

Gear ratios are as follows: First, 4.212; Second, 2.637; Third, 1.800; Fourth, 1.386; Fifth, 1:1; Sixth, 0.772. Reverse gear ratio is 3.385.

Ultracompact design

Compact packaging was a key design bogey. According to Ki Been Lim, Principal Research Engineer for Automatic Transmissions at Hyundai-Kia Motors' Corporate Research & Development Division in South Korea, the A6MF2's "super flat" torque converter is 12 mm (0.47-in) shorter and is 0.7 kg (1.5 lb) lighter than the torque converter used in the five-speed.

The converter is supplied by Exedy Corp. of Japan.

Overall the transmission is 12 kg (26 lb) lighter than its five-speed predecessor, said Juriga.

The A6MF2 has an adjustable hydraulic pressure control unit in the valve body.

"During the valve body assembly, having the ability to adjust valve body pressure to a desired pressure point helps us achieve desired shift quality character," said Juriga. "This is definitely unique. We've not done this with any of our transmissions in the past."

Among other technical highlights is a four-pinion differential gear vs. two pinion gears on the five-speed. And the electronic controls harness module for the valve body is designed as a single unit vs. the six individual clips on the five-speed's harness.

Durability testing entailed driving each of several Hyundai vehicles equipped with the A6MF2 a total of 120,000 mi (193,120 km). For a benchmark comparison, a Hyundai vehicle and a Toyota Camry were driven 160,000 mi (257,500 km) on city streets and highways.

Following the testing, both the Hyundai and Toyota transmissions were disassembled. "We found that our product, even after 160,000 miles, had no degradation in shift quality or in its functionality," said Juriga.

Customers voiced their thoughts about the new transmission during clinics.

"When we did the 2011 Sonata clinic, which included cars equipped with the six-speed automatic transmission, we picked Honda Accord, Toyota Camry, Chevrolet Malibu, and Ford Fusion owners biasing toward the gender mix and age mix of our market segment," Juriga explained. "A lot of companies do these clinics, but our engineers run the clinics, they collect the data, and they interview the drivers."

Eight weeks before the start of production a recurring theme was heard. Customers said the transmission was not responsive on all downshifts, according to Juriga. "Some companies would have said, 'OK, that's fine, but we'll wait to address that.' We made the calibration changes."

Juriga acknowledged the risk in making last-minute changes—unintended consequences being one potential result. "So you have to be very careful in what you do. But the objective was clear: You have to have the right product coming to the marketplace," he said.

In addition to being available on the Sonata, the A6MF2 will be offered on other future Hyundai and Kia vehicles, including the Santa Fe crossover and the Azera midsize sedan.

The 2011 Sonata also features Hyundai's new four-cylinder, 2.4-L Theta II engine with gasoline direct injection technology (reported in a separate AEI story).

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