General Motors upped this week's total investment in its new six-speed automatics to $500 million with Thursday's announcement that it was investing over $330 million in an upgrade to its Warren, Michigan plant, which will produce compact FWD and AWD models of the new transmission.

All told, GM's investment in the design, development and production of the new model automatics now stands at $1.7 billion.

The Warren plant will produce the new Hydra-Matic 6T70 and 6T75 six-speeds (pictured at right) for GM's midsize sedans and crossovers, including the Saturn Aura, Pontiac G6, Saturn Outlook, GMC Acadia and Buick Enclave. The new transmission debuts in 2007 models.

As in the bigger versions of the six-speed, a low first gear improves launch performance while an overdrive sixth gear boosts highway fuel economy.

The the mechanical elements of the new transaxle were co-developed by GM and (gasp!) Ford, but the controls, calibrations and operation of the transmission are unique to each company.

[Source: GM]

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GM invests another $170 million in shift to six-speed automatics