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Notes From the Road

Shifting Gears
By Kevin Clemens

End of the Manual?
It's a good thing that automatic transmissions have gotten so good, because the traditional manual transmission has started to fade into history, mainly as a result of government regulations. More stringent standards for fuel economy and exhaust emissions threaten the practice of shifting for yourself. Engineers charged with meeting these standards would much rather program a transmission control computer for every conceivable driving need than let an unpredictable driver make those choices. Fortunately, there are now new technologies that are giving shifting for yourself a reprieve...albeit in a much different form.
Manually Controlled Automatics
Even the earliest automatic transmission could be manually controlled by the driver for better performance or to hold lower gears while descending steep hills. In the 1980s, engineers began to develop better manual controls for automatics so that a sporting driver could manipulate the shifting more readily.
Ultimately, this has led to sophisticated computer-controlled automatic transmissions that can be operated in fully automatic mode or can be switched into a driver-controlled manual mode. Manual shifts are accomplished through either a console-mounted lever (often pushed forward or back) or by upshift and downshift buttons or paddles located on the steering wheel. Although these advanced transmissions are still automatics, which mean they still rob some power during their operation, they now allow the driver significant vehicle control.
A new breed of transmission has been introduced recently, which is far more of a hybrid between traditional automatic and traditional manual transmissions. Instead of using a torque converter, which absorbs energy, a standard clutch from a manual transmission is fitted and its operation is fully automated. This new electro-hydraulic system eliminates the need for a clutch pedal, but allows full manual shifting and, with advanced computer control, fully automatic shifting.
The driver controls the entire system through upshift and downshift buttons on the steering wheel or with a console-mounted lever. While manual shifting with these systems is immediate and satisfying, in automatic mode sensitive drivers may notice a lack of smoothness in the shifts compared to the latest automatics. Still, these systems are usually far more involving for the shift-it-yourself enthusiast compared to driving manually controlled automatics.
Four, Five, Six, Seven
Today, manuals and automatics are available with five or six forward speeds. In one case, a luxury automaker now offers a seven-speed automatic. Why the increase in the number of forward speeds? The idea is to provide an optimum gear ratio for almost any combination of road condition and engine speed, to provide scintillating performance while also meeting the latest exhaust emissions and fuel economy standards.
A modern six-speed transmission for example - whether manual or automatic - might have overdrive ratios on the two top gears so the engine will rev more slowly at highway speeds for better fuel economy. For the enthusiast driver, this increase in the number of forward gears also means that the gear ratios of the lower gears can be "shorter" (giving higher engine revs at lower speeds) and more closely spaced to provide faster acceleration and higher performance. Performance and fuel economy: The best of both worlds!
A Shifting Future
In many ways, the elements for future transmission technologies are already in place. It's hard to imagine the need for more than six or seven speeds (although more than five seemed absurd just a decade or two ago). Technologies that provide nearly seamless shifting and higher efficiencies are already here. Refinement of the existing technologies to further improve control and shift quality will undoubtedly remain the primary goals for powertrain engineers during the upcoming decade.
For those who like to use a traditional manual transmission, sadly, availability will continue to decline. The good news is that the application of new automatic transmission technologies will still give those who want to the ability to shift for themselves.
Kevin Clemens has both undergraduate and graduate degrees in engineering and has authored several patents. A former Product Public Relations Director for Michelin Tires and Technical Editor at "Automobile Magazine," Kevin writes for "European Car" and other publications when not competing rallies in various parts of the world with his vintage automobiles.

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