Consumers used to have two transmission choices: manual or automatic. In the late 1930s, the general public didn’t know or care how many speeds the magnificent early Hydra-Matic Drive automatics had. And they didn’t understand their mind-numbing complexity. They just knew they didn’t have to shift manually anymore and that was wonderful.
In a session at the recent SAE World Congress titled: “The Coming Onslaught of New Transmission Technology,” it appears little has changed from the early days. Automakers are introducing an avalanche of new powertrain technology, and the transmission folks are doing their best to keep consumers blissfully unaware of the mechanical and hydraulic acrobatics going on between the crankshaft and the wheels.
Except for the improved fuel economy and reduced emissions these engineering gymnastics deliver, of course.
CAFE and emissions rules are causing engine cylinder counts to drop but transmission gears to increase. While 2-, 3- and 4-speed automatic transmissions were good solutions for decades, 7-, 8-, 9- and 10-speed automatic step transmissions will be necessary in the future, says Charles Gray, director-Transmission and Driveline Engineering at Ford.
Electronic controls will help prevent these transmissions from shifting too often and being overly busy, but GPS systems, topographical maps and machine intelligence also will be employed in the future to anticipate loads and schedule gear changes to maximum advantage.
When looking at the vehicle electrification trend and a global carbon-dioxide reduction strategy, CVTs make a lot of sense, says Yutaka Fujimoto, director-Powertrain, Nissan Technical Center North America.
Even though CVTs are not as mechanically efficient as competitive transmissions, their infinite gear ratios enable engines to spend more time in their most efficient operating ranges, in which case they can deliver the highest-efficiency engine/transmission solution. “It doesn’t make sense to think of the transmission by itself,” Fujimoto says.
However, as transmission engineers seek to create the most-efficient, smoothest-shifting transmissions while they are being connected to increasingly rambunctious and power-dense engines with fewer and fewer cylinders, cultural and regional preferences further complicate their jobs.
CVTs are popular in Asia, and with Asian automakers, because of their efficiency, relative low cost and smoothness. Typical driving patterns involve mostly slow urban traffic and long stoplights. But U.S. and European drivers who do more long-distance high-speed driving find most CVTs boring.
Meanwhile, dual-clutch transmissions have superb mechanical efficiency and are popular with European drivers, and European automakers, because of their efficiency and sporty driving characteristics. But DCTs can feel abrupt and shudder slightly during launch like manual transmissions.
European and Asian consumers, most of whom are used to manual transmissions, don’t see this as a problem. On the other hand, Americans who grew up driving automatics with buttery smooth torque-converter launches complain DCTs feel harsh, especially lower-cost dry-clutch versions.
Hyundai is a bit of a transmission renegade in the sense that it is an Asian automaker committing heavily to DCTs for global markets. However, John Juriga, director-Powertrain, Hyundai America Technical Center, says the Korean automaker is applying numerous technologies to mitigate harshness while enhancing fun-to-drive characteristics.
In a nutshell, transmission engineers are slaving away in the trenches to meet 2020 and 2025 CAFE targets, yet they get none of the credit or glory the engine folks do.
With some pain in his voice, Ford’s Gray says one of his colleagues describes the transmission as a “filter” for the engine. One can imagine the colleague is thinking of the angry, jumbled kilowatts coming from the crankshaft as fine liquor that just needs to be gently “filtered” one more time before sipped, instead of corralled and tamed like a wild animal with a chair and bullwhip before it gets to the wheels.
Where will the number of transmission gears end? Ford’s 10-speed automatic looks like the top number for now, but you just know there is a chief engineer somewhere saying: “Let’s turn it up to 11.”
So, for those about to shift, we salute you. Thanks to the efforts of thousands of modest engineers working in the shadow of the great engines they serve, you will be saving the planet with every gear change without even knowing it.
