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Transmission Technologies

Photo of continuously variable transmission

Most conventional transmission systems control the ratio between engine speed and wheel speed using a fixed number of metal gears.

Rather than using gears, the CVTs use a pair of variable-diameter pulleys connected by a belt or chain that can produce an infinite number of engine/wheel speed ratios. Advantages include

  • Seamless acceleration without the jerk or jolt from changing gears
  • No frequent downshifting or "gear hunting" on hills
  • Better fuel efficiency

For more information, see How CVTs Work.

Potential Efficiency Improvement: 6%
Savings Over Vehicle Lifetime: $1,800*

Automated manual transmissions combine the best features of manual and automatic transmissions. Manual transmissions are lighter than conventional automatic transmissions and suffer fewer energy losses. However, most drivers prefer the convenience of an automatic.

AMT operates similarly to a manual transmission except that it does not require clutch actuation or shifting by the driver. Automatic shifting is controlled electronically (shift-by-wire) and performed by a hydraulic system or electric motor. In addition, technologies can be employed to make the shifting process smoother than conventional manual transmissions.

Potential Efficiency Improvement: 7%
Savings Over Vehicle Lifetime: $2,100*

* Fuel cost savings are estimated assuming an average vehicle lifetime of 185,000 miles, a fuel price of $3.44, and an average fuel economy of 21 MPG. All estimates are rounded to the nearest hundred dollars.

Data Sources

Potential fuel efficiency improvement:
Energy and Environmental Analysis, Inc. 2005. Automotive Technology Cost and Benefit Estimates. Arlington, Virginia, March.

Average light-duty vehicle fuel economy:
Heavenrich, R. M. 2005. Light-Duty Automotive Technology and Fuel Economy Trends: 1975 Through 2005. Office of Transportation and Air Quality, U.S. Environmental Protection Agency, Washington, D.C.

Average vehicle lifetime:
Calculated based on Transportation Energy Data Book, Edition 24. Oak Ridge National Laboratory, Oak Ridge, Tennessee, Tables 3.9 & 8.13.