With Exceptions, Semiautomatic Transmissions Perform Semi-Well

Consider the automatic transmission. Since Oldsmobile first mass-marketed it in 1939, its hydraulics, bands and torque converters have been propelling motorists down the road with no more action by the driver than moving the shifter from P to D. Left feet remain at rest and right hands and arms are free to serve other needs, be it radio or coffee or close personal friend in the passenger seat.

What was once revolutionary has become routine for most American motorists. Indeed, figures from Ward’s Automotive Reports show that 89.4% of all cars built in the U.S. last year had automatics. The figure for light trucks--minivans, pickups and sport-utility vehicles--was 87.2%. (Compare that with the rest of the world, where only 12% of Western European, 45% of Asia-Pacific and 2% of South American vehicles use automatic transmissions, according to PricewaterhouseCoopers.)

Purists, die-hard four-wheelers and those who desire more control on bad driving surfaces make up the remaining--and dwindling--American market for manual transmissions.

Although the automatic transmission remains convenient--and certainly makes learning to drive easier--it has never been especially efficient or fast. It takes control of engine speed beyond what the throttle asks. Of course, you could shift your automatic from 2 to 1 to D, or even 2 to 1 to D2 to D, but the quickness of this clutchless shift is more than offset by the transmission’s primary limitation: Only so much power can be transmitted from engine to drive shaft so quickly.

After all, a certain amount of slippage is built in by use of a torque converter, which amounts to two fans in a bath of hydraulic fluid. The fan turned by the engine creates enough pressure to turn the fan coupled to the transmission. Enough slip exists so that the engine can idle at stop with the transmission engaged. As more torque is converted from the engine to the transmission, the gearing changes without driver intervention.

Modern torque converters lock at highway speeds to increase efficiency. Some lock completely, some don’t. Performance and smoothness of shifting have been improved during the ‘90s by the computerized controller, which monitors some driving conditions, but most automatics are still slower and less flexible to drive than a manual.

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Which brings us to the semiautomatic transmission, which in theory combines the best attributes of automatic and manual modes and is enjoying a modest revival these days.

Variations of the semiautomatic--which usually means no clutch pedal but you still have to shift--have come and gone.

Among the earliest was Chrysler’s Fluid Drive, which was available from 1940 to ‘53, and has been described as the technological ancestor of Porsche’s current Tiptronic, a sophisticated multi-mode automatic transmission. (Having driven a ’49 Chrysler with Fluid Drive on more than one occasion, I can say it was a lot closer to “Driving Miss Daisy” than driving Daytona.)

Another notable entry in this vein was Sportmatic, introduced on the Porsche 911 in 1968 and some later Volkswagens. The motoring press didn’t like it, and neither did the buying public.

Street versions of clutchless shifting--which have benefited from enhancements developed for the racetrack--vary in complexity and in the amount of control given to the driver in the semi-auto mode. Ferrari’s version, for example, offers four distinct modes, from full automatic to clutchless shifting, that are completely at the driver’s discretion.

Before the purists scoff, consider that Ferrari believes this transmission to be a performance enhancement because it prevents missed shifts and over-revving and is quicker than a human. It doesn’t use a torque converter, relying instead on a standard clutch operated by a computer--which even blips the throttle and double-clutches.

Although the Porsche Carrera Tiptronic isn’t as quick to speed as the standard six-speed manual, it is slightly faster from 50 to 70 mph. Its sophisticated electronics monitor car and driver, anticipates the latter’s actions and shifts accordingly.

Increasingly during the last nine years, exotic, luxury and near-luxury cars have adopted their own versions of automatic transmissions that also work in semi-manual mode or use computer controls to more accurately pick gears. Interestingly, the U.S.-made Lincoln LS comes with a five-speed manual as standard; SelectShift, Lincoln’s five-speed automatic with clutchless shifting, is an option on the V-8 model. This at a time when some European and Japanese high-end marques don’t even offer a manual transmission, at least not to the American market.

Oddly enough, among the few cars that do offer manual transmissions, more six-speed gearboxes are appearing.

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So with Americans’ appetite for automatic transmissions and desire for performance, you might think that something akin to Tiptronic would become available in moderately priced cars.

Alas, that doesn’t appear to be in the offing.

To be sure, Tiptronic is an option on the Passat, the popular mid-size from Volkswagen, Porsche’s frugal cousin. But where Japanese luxury marques Lexus and Acura offer multi-mode automatics on their top sedans, touring models and sports cars, nothing like it is available in their parent Toyota or Honda lines.

“It’s not moving down-market here in the U.S.,” says Pete Langlois, senior consultant for PricewaterhouseCoopers’ AutoFacts Group. “And it’s not particularly catching on in Europe, where it’s on high-end cars and some economy cars, but for very different reasons.”

European economy cars often have automatics because of development and manufacturing costs, he explains.

Langlois considers the interface on a lot of the multi-mode automatics to be nothing more than a gimmick: Performance isn’t any different from that of run-of-the-mill auto gearboxes; the driver just gets to be more involved.

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I prefer a manual transmission, though I have not had the opportunity to drive a Tiptronic Porsche or any of the similar gearboxes. I suppose I could be converted, but I enjoy shifting gears as part of driving my Mazda Miata roadster. For me, convenience is a distant second to control and road feel. I don’t even care for power steering in sports cars, not even on the BMW M roadster.

That said, however, when Mrs. G and I needed to replace our aging SUV, the vehicle we chose was an all-wheel-drive Subaru Legacy Outback wagon with automatic transmission and, unavoidably, power steering.

The advantage in this case is that the traction-control computer works with the automatic transmission’s computer to shift power as much as 80% to the rear, 20% to the front. That’s the opposite of the normal distribution. The manual transmission model always divides power 50-50 regardless of what the traction-control system senses at the wheels.

Porsche’s all-wheel-drive 911 Carrera 4 with Tiptronic is one of the most heavily computerized cars in the world. In its most sophisticated incarnation, it includes anti-lock brakes, individual-wheel braking, anti-wheel slip and a stability-management system that uses sensors to determine direction, speed, yaw, velocity and lateral acceleration.

If the computer doesn’t like what the sensors say, it brakes individual wheels to bring the car back on line. If braking isn’t enough, it’ll tell the engine’s computer to make adjustments. With the Tiptronic gearbox, the system can also use the transmission to stabilize the car by shifting power front to back or vice versa.

This is about as close to autopilot as you’ll see in this century.

Do you have a question or suggestion? Write to Dr. Gear Head, Business Section, Los Angeles Times, Times Mirror Square, Los Angeles, CA 90053. Fax: (213) 237-7837. E-mail: gearhead@latimes.com. Please include your full name, address and daytime telephone number.