ZF: 9-Speed Automatic Matches Dual-Clutch Gearboxes

The 9-speed automatic transmission Chrysler Group LLC is introducing this year matches the efficiency of dual-clutch units, according to developer ZF Friedrichshafen AG.

ZF says the new gearbox delivers about 16% better fuel economy than a 6-speed transmission the same improvement possible with a dual-clutch design but with significantly better start-up acceleration.

Packaging nine gears into a transverse front-drive transmission layout demanded an unusually compact configuration. The ZF design puts two planetary gear sets on top of each other, so there are never more than three gear sets in a row. Hydraulically operated constant-mesh elements also save space.

The new transmission uses a combination of dog clutches, multi-disc clutches and multi-disc brakes. The dog clutches eliminate parasitic drag causes by open multi-disk clutches. ZF claims the configuration results in planetary gear sets that are more than 97% efficient.

Multiple clutches and brakes also permit gear shift times equivalent to twin-clutch transmissions, according to the company. The architecture also enables the ability to reprogram shift times, allowing the driver to select comfort or sport modes.

Chrysler will produce the 9-speed in two sizes that cover the carmaker's entire range of front-drive, transverse engines. An optional transfer case enables all-wheel drive. ZF says the configuration incorporates a decoupling system that contributes a 5% fuel savings by engaging AWD only when needed.

Chrysler says it may equip as many as 200,000 vehicles this year with the 9-speed, starting with the next-generation Jeep Liberty SUV arriving in mid-2013.