The use of continuously variable transmissions (CVT) has recently received increased attention due to their many benefits, like better fuel efficiency and quick acceleration. Surprisingly, CVTs aren't new technology.
"I saw my first CVT back in the 1960s on a little car made in Holland," Keith Johnson, senior automotive training instructor for American Honda Motor Co., Inc. says. "The company was DAF—now owned by Volvo—and the car's name was Daffodil 32. The CVT is a really unique concept, and has been tried by various manufacturers with varied success."
Before manufacturers started experimenting with CVTs in cars, Johnson says he saw the principle applied to very low horsepower applications like snowmobiles in the 60's and 70's back in Minnesota.
"Those belts were rubber, and in a situation where you would have people racing the snow mobiles, the belts would burn up because it couldn't handle the horsepower.
"When you start increasing the horsepower in a car engine, that belt mechanism has to be built sturdier." Johnson says most belts are now made of metal links like a watch band. Those little links are actually what make the CVT operate.
WHAT'S THE DIFFERENCE?
According to Jim Groat, technical development training manager for Ford Motor Company, a CVT works so well because it allows the engine to be in its most efficient power band a larger percentage of the time.
"The motor is not constantly trying to work harder to meet its power band, and so it really saves energy," he says.
Natae Cutler, product education and development for Toyota, explains that the spin rate of the engine can be selected to produce required power, but the spin is no faster than necessary, so that it maintains fuel efficiency and reduces exhaust emissions.
"With a CVT, it allows for the power to be revved really high while it lowers the engine spin rate to reduce losses associated with fast moving internal engine parts," she says.
It is important for fleets to keep in mind, when servicing CVTs, each manufacturer has its own modified version.
"We simply use a planetary gear unit that gives similar effects of a CVT. We don't have the belts and the pulleys that can loosen up or be damaged within the vehicle," Toyota's Cutler explains.
Yellow Cab Company in San Francisco is among the early adopters to run fifteen Ford Hybrid Escapes in their fleet. Each Escape has Ford's hybrid modified version of their CVT. Adnan Atallah, shop manager at Yellow Cab Company, says their warranty is up at 100,000 miles; that's still a good three to five months away for Yellow Cab.
"We haven't done any work on the modified CVTs, so we don't know how hard or how easy it is to work on. We change the oil, check the brakes—most of the preventative maintenance items are still the same. We just send it to the dealer when it pertains to the CVTs," he says.
Groat says Ford's CVTs are really very simple to work on.
"There are a few main components. Once you understand the principle on how they operate, CVTs are very easy to work with."
"They do require some special tools, as do most automatic transmissions," Groat says. "There is a large tool that is used to put together the variators on the transmission that would need to be purchased to service the internal components of the transmissions. Most of the failures that are likely to occur have something to do with the valve body, and that doesn't really require the assistance of special tools."
BACK TO SCHOOL
Despite the small number of CVTs Yellow pare his techs for additional training once the warranties expire.
"For some training information, we will go back to the dealer for seminars and general information. For larger components, we expect Ford's training personnel to come here and do their training in house," he says.
Groat explains that offering training information on vehicles has become an industry standard.
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