Transmission engineers are shifting to higher gears
Automakers are spending billions of dollars to squeeze efficiency from a car part most people never think twice about — the transmission.
Over the next five years, many new vehicles will have transmissions with up to 10 speeds, replacing the mostly six-speed transmissions in cars now. Though designed for refinement and performance, the transmissions aim mostly to help meet stricter federal fuel economy and pollution standards.
“We are trying to extract efficiency out of every subsystem of the vehicle,†said Mircea Gradu, vice president of transmission and driveline engineering at Chrysler Group. “There are very aggressive targets that are in front of us.â€
This year, Chrysler has already added eight-speed transmissions to some of its Ram trucks and a couple of Chrysler sedans. It plans to put a nine-speed gearbox in the Jeep Grand Cherokee and Dodge Dart.
General Motors Co. and Ford Motor Co. launched a joint project last month to create nine-speed and 10-speed transmissions for their cars and trucks.
By 2020, transmissions with more than seven speeds will be found in 54% of new vehicles, up from just 2% in 2010, according to forecasts from research firm IHS Automotive.
The transmission investments give automakers “bang for the buck,†Gradu said, with as much as 10% fuel savings.
“Transmissions are among the lower hanging fruit,†said Roland Hwang, transportation program director for the Natural Resources Defense Council.
The new gearboxes allow engines to operate in a sweet spot for the task at hand, whether speeding up a highway onramp, cruising at 65 mph or towing a boat. At highway speeds, an eight-speed transmission reduces the engine’s revolutions per minute from 2,000 in a six-speed gearbox to about 1,700 rpm, depending on engine size.
Drivers should notice a smoother ride because engines won’t work as hard. The jumps, or steps, between gears will be smaller, making shifts less abrupt. Extra gears also keep the engine from needlessly lugging or revving.
The transmissions provide another example of government regulations spurring industry innovation, Hwang said.
“Not only are you saving money on gasoline, but you are also getting technology that will give you a better driving experience,†he said.
Gabriel Shenhar, the senior auto test engineer at Consumer Reports, agrees.
“We have driven many of the eight-speed transmissions, and they are terrific,†Shenhar said. “They shift imperceptibly and are very quick. The transmission is almost reading your mind, figuring out the terrain you are driving through and knowing your position on the gas pedal.â€
When he first noticed automakers adding gears, Shenhar sensed a marketing ploy.
“Five years ago, we thought this was just one-upmanship,†he recalled.
Then, a seven-speed transmission was the most advanced, Shenhar said. But Toyota soon installed an impressive eight-speed transmission in the Lexus LS.
“Now, we think the new multispeed transmissions are terrific and set a new benchmark,†Shenhar said.
Craig Renneker, Ford’s chief transmission engineer, was another skeptic. He admits that he once didn’t believe that nine- and 10-speed transmissions were feasible. Now he’s designing them.
Several improvements paved the way for more gears, reducing drag on moving parts. Engineers have improved the flow of lubricants inside gearboxes, limiting friction. They also are able to use thinner oil and to better control its viscosity.
At the same time, Renneker said, new software allows for more precise shifting and more complicated transitions between gears.
At a transmission conference in a Detroit suburb earlier this week, engineers from all the major automakers and suppliers met to discuss the looming fuel economy regulations and automotive improvements. They debated the “hot question†of whether transmissions would continue to add gears beyond the current 10 speeds.
“Are we done with the speed race?†he asked. “The short answer is, we just don’t know at this point.â€
