Continuously variable transmissions (CVT).

Dear Car Talk

Dear Car Talk | Nov 01, 2004

Dear Tom and Ray:

What is CVT, or continuously variable transmission? I am thinking about getting a new car, and I am looking at the Mini Cooper. But I only know how to drive an automatic (and I can't find anyone who will teach me how to drive a manual on his or her own car!). Will paying an extra $1,300 for a CVT on the Mini Cooper solve my problem? Thanks much in advance! -- Kari

RAY: Yes, that will solve your problem, Kari. The CVT is an automatic transmission; it's just a different, more efficient kind of automatic transmission.

TOM: In the really old days, automatic transmissions had two gears. Then three, then four and now five, six and soon, even seven. You can see where the trend is going here, can't you, Kari?

RAY: Well, a continuously variable transmission has an infinite number of gears. Instead of having "fixed" gears, like First, Second and Third, with specific gear ratios, a CVT simply "slides" along a continuum, from higher ratios to lower ratios depending on what the car needs at any given moment.

TOM: Here's a simplified explanation of how it works: Imagine that you strung a rubber band around an ice-cream cone (no ice cream -- that would lead to a messy transmission rebuild). Anyway, as the cone turns, it turns the rubber band, which moves the wheels. Now, when the rubber band is at the top, the widest part of the cone, that would give you your highest gear ratio, for starting and climbing hills. And as the ice-cream cone turns, the rubber band moves smoothly to the thinner part of the cone. That's where you'd get the lowest ratios -- for cruising on the highway, for instance.

RAY: And since, theoretically, it can always adjust itself to the perfect gear ratio at any time, it's more efficient than a standard automatic transmission, and gives you better gas mileage. And no jerky shifting.

TOM: But most importantly to you, Kari, it operates just like an automatic transmission, from the driver's point of view. That is, you put it in Drive, step on the gas and fuggedaboutit. Enjoy your new Mini.

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