Choose a manual transmission for performance and economy or the automatic for convenience. It used to be that simple, but the world of transmissions has changed considerably in recent years, particularly as regards the latest wave of high-tech automatics. When researching new cars today you’ll run across a bewildering array of oddly named choices, including SMG, DSG, Xtronic, S-Tronic, Tiptronic, CVT and more. Traditional automatics now come with as many as six, seven or eight gears. Even the basic rules have changed. A manual transmission is no longer the most efficient and, in some cases, might not be the top-performing or even most fun-to-drive gearbox offered in a given line.
You’d think an advanced degree in mechanical engineering should be required before you’re permitted to buy your next car. But fortunately, it’s possible to understand the basics and advantages of the various types of transmissions without studying fluid viscosity, algorithm theory or toroidal rotation.
The traditional stick shift manual transmission is becoming rare. Still offered in sports and economy cars, manual shifting is simply losing popularity. Inching along in traffic can be annoying and it wears out the clutch prematurely. As fewer people request them, dealerships are rarely even ordering cars equipped with manuals. As modern automatics and other alternatives improve, there is often no advantage in fuel efficiency by taking gear changes into your own hand.
Traditional automatics have improved in a myriad of ways. Enhanced internal components help efficiency while the microchip provides more precise control to manage smoother and faster shifting. Adding more gears smoothes shift shock and enables more-precise engine tuning. How many gears do you need? There are some very smooth-shifting, four-speed transmissions and jerky six-speed units, so it’s more than just a numbers game. Many modern automatics offer manual controls that let you shift at will by pushing the shift lever or tapping a paddle near the steering wheel. There remains a wide variance in response speed among brands, however. Thus the test drive still remains a more important determining factor on which to choose than is merely reading the brochure specs.
A growing and promising technology is the CVT, which stands for continuously variable transmission. A CVT has an infinite number of gear ratios because it eschews gears for a system of belts and pulleys. Unfortunately, the earliest CVTs proved to be fragile, and a number of brands abandoned them. The latest offerings are proving superior, however. Nissan now offers the widest array of CVT-equipped vehicles and is the only major manufacturer equipping so many four- and six-cylinder cars with CVTs in both front- and all-wheel-drive models. Factory engineers can more easily adjust shift points on a CVT and many have a sport mode and manual-operation paddles that mimic quick shifts to provide additional driver control.
Because of the nature and efficiency of CVTs, virtually all electric and hybrid vehicles are equipped with them. However, CVTs are still limited to smaller engines or, in some cases, midsize V6 power plants. But it may not be long before we see them in more-powerful vehicles.
The automated manual gearbox is an old idea that is being completely revitalized. Past attempts rarely proved successful but the latest iterations are showing remarkable potential. BMW brought its SMG to this market in 2002 as a clutchless manual that could be operated with paddles or placed in a fully automatic mode. It has been improved over the years, but still suffers from jerky shifts that make it a poor alternative to an automatic.
Meanwhile, Volkswagen and Audi recently began offering the DSG transmission (Audi, has since changed the name to S-Tronic). Technically, DSG is a manual transmission with not one, but two clutches. However, there is no driver’s clutch pedal. A computer operates the clutches for you. It can be operated in three modes. A manual mode permits the driver to shift up or down at will using either paddles on the steering wheel or by pushing the shift-lever forward or rearward. The other two modes operate as full automatics, one being a sport mode that maximizes acceleration at the expense of fuel efficiency.
Having the second clutch allows the next gear to be pre-selected so the transfer can be very smooth and very quick. In testing, the DSG has out-performed a manual transmission driven by the best race drivers in shift speed and acceleration. According to the EPA, it can also produce better fuel economy than a manual. Is it the best of both worlds? Some people think so. In fact, many enthusiast drivers are finding the extra precision more fun to drive while the automatic mode eases a commute in heavy traffic. This type of transmission helps solve the dilemma of a shared car where one person wants a manual and the other prefers an automatic.
In coming years, dual- or twin-clutch transmissions will become more widespread across product lines. Volkswagen has announced its intention to make it the sole transmission in most of its cars in the not-too-distant future. Other manufacturers are bringing out similar transmissions within the next year or two.
Whether it’s a traditional automatic, CVT or clutchless manual, all are benefiting from a system approach to transmissions. A computer makes decisions based upon input from various components that adjust the throttle, suspension and electronic stability control. This enables all the mobility systems of a car to work in unison, enabling improvements not just to performance, comfort and economy, but also to safety. The result is simply a better overall driving experience.
