Machine Design

Seven gears and counting

A seven-speed automatic transmission, said to be the world's first, makes its debut in select V8-powered Mercedes-Benz vehicles.

One notable feature — it will skip a gear if necessary, as when going from seventh to fifth, during downshifting for quick acceleration and, according to Mercedes, imperceptible shifts.

A hydrodynamic torque converter carries a special lockup clutch for maximum fuel efficiency. Also, while many cars lock up the converter in top gear only, this lockup clutch engages in all seven. A transmission computer networks to ABS and traction-control systems to recognize cornering and low-traction conditions. Based on feedback, the transmission may delay or speed up a shift to avoid any negative effects on stability or traction. The seven-speed transmission will be standard fare on the 2004 E500, S430, S500, CL500 coupe, and SL500 roadster.

 

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