GM's Next Six-Speed Autoshifter Promises Five-Percent Better MPG

By KBB.com Editors on August 20, 2009 6:35 AM

While the current-generation of GM's Hydra-Matic 6T40 automatic transmission (pictured here) does a most impressive job of enhancing the mileage-maxing potential of compact and mid-size vehicles, The General's powertrain engineers are already well along in the development of a new and improved 6T40 family that it anticipates will bump the transmission's overall operating efficiency by an additional five percent. According to GM, up to 60 percent of that extra gain will come from adopting even more precise control of the computer-programming side of the equation. The remaining 40 percent will be generated by improving the design of various hydraulic-related internal components like the main valve body, friction plates and variable-flow solenoid, elements that can sap energy without actually contributing to any forward motive force. Like the existing 6T40, this Gen II successor will retain its compact, lightweight overall design when it enters service in a year or so. In the meantime, GM is continuing an aggressive roll-out of six-speed automatics across its entire lineup. During the past four years, nine different variations of these more efficient gear changers have been added to the corporate mix. For 2010, 24 models will be equipped with some type of six-speed automatic and that number will rise to 34 by 2012 as part of GM's ongoing effort to meet increasingly stringent future EPA mileage requirements.

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