It wasn’t that long ago that a five-speed automatic transmission was considered a major automotive advancement. Now manufacturers are working together to develop 10-speed transmissions. Yet, six-speed transmissions still have their place.
The primary reasons for vehicles with more transmission speeds are fuel economy and performance. Automakers are under federal mandate to improve their corporate average fuel economy (CAFE) numbers, as well as greenhouse gas and carbon dioxide numbers, while consumers are demanding better performance.
It poses the question – what is the right transmission to buy? How do you choose among automatics, manuals and continuously variable transmissions, commonly known as CVTs?
According to one expert, the answer might surprise you. Michael C. Harley, editor-in-chief of AutoWeb and an industry veteran, says, “There really is no need for a consumer to worry about it. The end result is you are looking for smooth, fuel-efficient and reliable. For the average driver, the automatic transmission is most fuel-efficient.”
He acknowledges there is one exception. Diesel engines mated to manual transmissions have higher fuel economy numbers than their automatic transmission counterparts, Harley says.
Jeff Lux, Fiat Chrysler Automobiles vice president of transmission powertrain, thinks transmissions may have hit their peak in terms of numbers of gears. “If you would have asked me 15 to 20 years ago would there be more than four? More than six? My answer would have been no. There’s been a fair bit of technical work. We are probably approaching the limit. The benefit part of the curve gets pretty flat. I think we are reaching the end of a significant increase in the number of gears. They will do other things to extend the benefits for fuel economy.”
One of those other things would be start/stop technology. Basically, your car shuts off when, for example, you are stopped at a traffic light and take your foot off the accelerator. Step on the gas pedal and the engine turns back on. Shutting the engine off at idle saves fuel.
Technology has been developed to make start/stop more seamless for consumers, says Brad LaFaive, vice president for Global Sales and Business Development, Transmission Systems, at BorgWarner, which delivers powertrain components to manufacturers. “When we look at the future of transmission architectures, most all, if not all, are being designed to be start/stop to restart quickly and smoothly in a way customers will never notice,” he adds.
Harley, for one, understands the enthusiasts' desire for manual transmissions but downplays their significance when it comes to performance. “No matter who’s behind the wheel, [racing legend] Hurley Heywood or your grandmother, you can’t beat today’s automatic transmission.”
While there is a diminishing market for manual transmissions, CVTs play an increasing role. As Harley explains, they use a belt for unlimited gear ratios. They are noted mostly for their fuel efficiency because they can maneuver the engine’s speed for the best power and fuel efficiency.
Nissan says it sells, on a percentage basis, more CVTs than any other automaker in the American market. It has embraced the technology and plans to stick with it, says Steven Powers, who is a senior manager of engineering at Nissan’s Arizona testing facility. CVTs, he explains, work well in smaller front-wheel drive vehicles because they can be housed in smaller packages. That’s an important consideration because of the tight space of front-wheel drive architecture.
In addition to fuel efficiency, Powers says CVTs can be smoother than traditional automatic transmissions. He says smaller vehicles are limited to five- or six-speed automatic transmissions. They can’t have more gears because of packaging size. “When you have the lower number of gears, you have a bigger gap between the gears so your shift shock becomes worse. With CVTs you can achieve that smoothness,” he says.
He acknowledges CVTs might feel unusual to most consumers at first, because they lack the “click” of gear changes found with automatic transmissions. Nissan has designed a D-Step technology, first introduced in its 2016 Maxima, that replicates that shifting experience. “With the D-Step we can simulate as many gears as we want. We could have 20,” Powers says, adding that implementing that technology has had a negligible effect on the CVT’s fuel efficiency.
There’s another lesser-known advantage to transmissions with more gears: improved off-road capability. At Fiat Chrysler, the nine-speed transmission with the lower gear ratios helps make the new Jeep Renegade able to go off road, Lux says, because it provides a low crawl speed. “It’s a true off-road Jeep. That would have been more difficult with a six-speed transmission,” he adds.
At the end of the day, what matters most is the vehicle that feels most comfortable to you, whether your needs are for fuel efficiency or performance. “I don’t think the average consumer will notice transmissions beyond the automatic versus manual. Manufacturers have done the right job with aligning their transmissions with their cars,” says Harley.