General Motors new Hydra-Matic 6T70 six-speed automatic transmission, an advanced transmission with clutch-to-clutch shift operation for front- and all-wheel drive vehicles, will make its debut in the new 2007 model year Saturn Aura midsize sedan.
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Co-developed with Ford, the new six-speed joins the already announced Hydra-Matic six-speed rear-wheel drive family of automatics and Allison 1000 six-speed automatic as part of GM’s plan to produce three million six-speed automatics annually by 2010.
The 6T70’s clutch-to-clutch operation allows for reduced complexity and compact packaging. A wide, 6.04:1 overall ratio spread helps the transmission deliver both performance and fuel economy, enabling up to 8% improved performance and up to 4% improved fuel economy when compared with current front-wheel drive four-speed automatics.
The joint development effort between Ford and GM allowed both companies to maximise time and engineering talent to answer a common need for a fuel-efficient transmission that meets the performance needs of high-output, transverse-mount powertrains.
Co-development of the transmission allowed it to reach production in less time and enabled each company to reduce development costs by as much as 50%. A common design and many common components are shared between GM and Ford six-speed variants, but each company developed its own controls and calibrations to tailor the shift feel of the transmission to fit their brand characteristics.
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By GlobalDataRated for engines up to 315 horsepower and 280 lb.-ft. of torque, the 6T70 helps maximise powertrain performance and economy through its wide 6.04:1 ratio – the spread in gear ratios between first gear and sixth gear. This configuration allows for a ‘steep’ 4.48:1 first gear, which helps deliver exceptional launch feel, and a 0.74:1 overdrive sixth gear – the ‘tall’ overdrive gear lowers rpm at high speeds, reducing noise, vibration and harshness. Fifth gear is 1:1 or direct drive.
Shorter steps between the gears, compared with a four-speed automatic, enhance performance and feel, as the transmission quickly finds the best gear for the vehicle speed and road conditions – there’s less “hunting” (shift busyness) on grades, for example. Also, the 6T70 offers the capability of driver shift control (DSC), which allows the driver to use tap-up, tap-down shifting to select the desired gear for specific road conditions, such as driving up a steep hill.
The Hydra-Matic 6T70 will be manufactured at GM’s Warren Transmission plant from summer 2006, when production of the Saturn Aura begins.
