Continuously Variable Transmissions

Scott: Hi, everybody, and welcome to the podcast. I'm Scott Benjamin, the Auto Editor here at howstuffworks. And I'm here as always with Ben. How are you doing today, Ben?

Ben: I'm doing super well, Scott. How are you doing?

Scott: Also super well. Super well. That's a good one. I've never heard you use that one.

Ben: You know, I just pulled it out, but I - I don't know. I - I think it works. How do you feel about it?

Scott: I feel okay.

Ben: Great intro, by the way.

Scott: Oh, I appreciate it. I'm trying them out, and I think it's going smooth, so.

Ben: Knocking them out of the park, my friend.

Scott: Anyways, I'm not smooth with the transitions like you are, so I'm just gonna say we're gonna talk about some transmissions today.

Ben: Transmissions. Okay. So -

Scott: Yeah, transmissions.

Ben: - that's perfect. Let's get into it because we've done some speculative podcasts, but let's get into some nuts and bolts. First, I guess, for everyone out there who happens not to know, what is a transmission and what does it do?

Scott: You know what? I'm sorry, Ben. Here's what I'm gonna do.

Ben: What?

Scott: I'm gonna back up for just one second, okay?

Ben: All right.

Scott: Excellent question.

Ben: Okay.

Scott: I'm gonna back up and say that this is a listener request. I - I neglected that. I just peeled off a Post-it note, and I - I saw my notes here that say that it is a listener request. And I feel we need to tell them that.

Ben: Yeah.

Scott: It was actually from two listeners, and these are going way back, s sometimes happens. Someone named Zack and also someone named Rajan wrote in and said that they would like to hear some information about CVTs, in particular.

Ben: Continuously variable transmission.

Scott: See, you know what I'm going - going for there.

Ben: Okay.

Scott: Continuously variable transmissions and actually they had questions about a lot of different transmissions. We're gonna focus on CVTs, in particular in this episode.

Ben: Okay.

Scott: So - so Zack and Rajan, this one's for you and also for everybody else.

Ben: Thanks for writing in, guys. We love listener mail.

Scott: Oh, by the way, Rajan's from India.

Ben: India?

Scott: Yeah. Mumbai, India.

Ben: That is awesome.

Scott: Yeah. Pretty cool. We have listeners all the way out in India.

Ben: Yes. And we think all of them are fantastic, wherever you're from.

Scott: Of course.

Ben: I guess everybody listening to this is from the internet in one way or another.

Scott: I guess it's just pretty amazing to me to understand that what we do here, what we're recording, is truly going around the world and everybody's really paying attention.

Ben: Well, everybody loves cars, man.

Scott: I don't know. That's interesting.

Ben: Okay. Most people love vehicles.

Scott: Okay. Let's - enough - enough patting ourselves on the back. That's - that was pretty cool, though, I thought. So anyways, we can get right into it, and we'll talk about CVTs if you'd like.

Ben: I'd love to.

Scott: Okay.

Ben: Yes, break it down for me.

Scott: Well, you had a question for me. Right?

Ben: I did. I did. Just - just to establish some parameters. What are transmissions and what do they do on a car?

Scott: Simple enough.

Ben: All right.

Scott: Transmission, every vehicle has one, really. Almost every vehicle has one. All they do, really, is just they change the - the speed - the ratio coming from the engine speed to the wheels. I probably just goofed that up, but close enough. What - what it does is it makes the power coming from the engine useable at the wheels because if you didn't have any gearing in between - it's - it's a gear box, really - and if you didn't have any gearing in between you would have basically one gear between the engine and - and the wheels. And it would be whatever speed the engine is going.

Ben: So does this modify torque?

Scott: It does. It does. You're right. So it's - it's a twisting force that is then converted - well, it remains a twisting force all the way to the wheels, actually. But it - it is modified into useable rat ios that can be helpful for accelerating, climbing hills, going down hills, just top speed, any driving situation, really, because you need all these different ratios in order to do that effectively.

Ben: Now, you know where I'm going with this.

Scott: I think I do. Yeah.

Ben: That - that's a basic transmission.

Scott: That is a basic transmission. Yeah.

Ben: What makes a CVT different?

Scott: CVT, and it's really popular right now. We'll talk about that in a minute, too, but a CVT is a continuously variable transmission. And what's - what's unique about a CVT is that it doesn't have any stepped gears, any - any specific hard set of gears where this is always gonna be the ratio when you're in this gear.

Ben: Oh, okay.

Scott: Continuously variable transmission, just as the name suggests, it's continuously variable. It has an infinite number of ratios, and we'll describe how that's possible in a minute, but an infinite number of ratios that are accessible at any point, really. It's able to adjust to your driving pattern or - I guess I should say more to the - to what you're asking it to do.

Ben: The driving conditions.

Scott: Driving conditions, that's a better - that's a better way to say that.

Ben: How, exactly, does that work? That seems very difficult.

Scott: Well, there are three different types. There are three different types of CVTs.

Ben: Okay.

Scott: And we're gonna focus on the most common type, which is the pulley type. The pulley type is the kind that you'll find in automobiles right now.

Ben: Okay.

Scott: There are several other different types. There is a - I'm gonna mess up the name of this, but I have a hard time saying this word, Ben.

Ben: All right.

Scott: Toroidal, which is T-O-R-O-I-D-A-L, toroidal -

Ben: Toroidal. Okay.

Scott: - CVT, which has no pulleys. It uses discs and power rollers. And it's really - I mean, you're gonna have to look these up just to see what they - what they look like. We've got an article about CVTs on our site, so check it out. You can find a good graphic of these there. And there's also a hydrostatic CVT, which uses variable displacement pumps or hydrostatic motors, so it uses the - it converts the rotation of the engine into - well, flow power, not flow power, but - but fluid flow. I don't know of a better way to say that.

Ben: Yeah.

Scott: But it - it uses pumps and fluid in order to - to make the whole system work. And again, check out - check out the site and you'll understand this. I - there's no way I can describe it right here what's going on.

Ben: You have to see it.

Scott: You do have to see it. Yeah.

Ben: Okay.

Scott: Anyways, hydrostatic motors, it's a little more complex than that, of course.

Ben: But luckily, for us, we're on the pulley.

Scott: The ones we're talking about are the pulley. Thanks for getting me back. The - the pulley system, now, let's see if I can describe this right. There are two - it's real simple. It doesn't have a whole set of gears like a - like a normal automatic transmission would. And we're not even talking about manual here because, really, a CVT is like an automatic. You don't shift a CVT other than if there is an option to do that, and some of them have the support shifting sections. We'll talk about that a little later, too, but basically, it's an automatic transmission. And there - really, it's so simple inside. There's a drive pulley and a driven pulley. Now, the drive pulley is connected to the crankshaft, which comes out of the engine. And the driven pulley is the one that transfers that energy to the drive shaft.

Ben: Okay.

Scott: So the crankshaft is the - the drive pulley. The one that connects to the drive shaft is the driven pulley and is the output. Between those two - and this is where it gets a little complex here - between those two for automotive purposes, there's a metal belt. It's a metal belt, which is kinda unique. The belt is fashioned of several bands that run together, maybe a dozen bands. And those are - and that's held together - all those bands are held together with these - it looks like metal keys, almost. And there's thousands - I'm gonna say 1,000, but it's probably more than that, I'm guessing, because there are that many of them in this belt. It's a very heavy belt, real heavy duty. And that's what runs between the two pulleys, and we'll describe the pulleys in a second, too, but I wanna tell you that a lot of CVTs that use this pulley system - they don't have to be in cars, by the way. CVTs have been around for a while. They've been in power tools, drill presses, tractors, snowmobiles, motorcycles, but they've all used rubber belts in between the pulleys. And so now, the difference is CVTs in cars, in order to handle all the torque and the power that - and just for durability, they use the steel - steel belts.

Ben: Wait, wait, wait one second.

Scott: Yeah?

Ben: Now, I - I have to ask you to step back for a second.

Scott: Uh-huh.

Ben: How recent or old is this technology? You said it's been around for a while, which kinda surprised me.

Scott: It - it's been around a long time. You wanna take a wild guess? Do you know? Do you know the answer or are you just messing with me? Because if you know -

Ben: I'm messing with you a little.

Scott: - if you know, come right out with it because it's - it's unbelievable when you hear it.

Ben: Okay. Call shenanigans on me if I'm wrong.

Scott: Yeah. Go ahead. Go ahead.

Ben: Leonardo da Vinci, really?

Scott: Really. Really.

Ben: That blows my mind.

Scott: 1490 is when Leonardo da Vinci, who we've talked about many times on this program how he's just - he's just u nbelievably advanced, early thinker. He sketched a step-less continuously variable transmission in 1490 if you can believe that.

Ben: I mean, I'm trying my best to believe it.

Scott: I have no idea what it looks like. I haven't seen this - the sketch or how it compares to what we actually have now.

Ben: So it had to be made of wood or something.

Scott: I don't know. I don't know. Stone. I don't know. Really, I don't know. Probably wood. Probably wood and - but I don't know - I mean, I'm guessing vines or something in between the pulleys. I don't - maybe it wasn't a pulley system. Maybe there's some other type of system. I don't know.

Ben: So 1490, that would make this hundreds and hundreds of years old.

Scott: 520 years old, at this point, something like that.

Ben: Man, yeah.

Scott: I mean ballpark. But I guess when you get down to it, though, it really wasn't built or - or in production. It's not really serving the purpose that it should.

Ben: Okay. Just conceived!

Scott: Yeah. That's right. It was conceived at that point in - you know what? I'm gonna go earlier than this. I got - I got a note here that says 1958 there was a car that used a CVT in the Netherlands, but I'm gonna go back even further, Ben.

Ben: Let's go back even further.

Scott: There's - there was a company called Zenith Motorcycles, and they originated in 1904.

Ben: Okay.

Scott: And Zenith Motorcycles had a device that they called a graduagear. It's like - almost like gradual without the L at the end, graduagear.

Ben: Okay.

Scott: And it used a variable pulley system that would vary the length of the - of the drive belt by moving the rear wheel forward and backward in its slot. And this apparently gave Zenith Motorcycles a - such a - an advantage at the time in this - in this hill climb competition that they were in or hill climb competitions. It gave the rider such an advantage that they were banned from competition. It was that much better than everything else that was out there.

Ben: Weird. That's -

Scott: A standard - standard shift.

Ben: That's weird. It's like you heard about the - I think they're German. There's a swimsuit company whose swimsuits have been banned from professional competitions because the improvement is that noticeable.

Scott: Isn't that something? I mean, I say great. Move on with - with technology.

Ben: Yeah.

Scott: But they held them back, I guess, but it didn't hold them back from producing the motorcycle. They still produced the - the motorcycle until, I believe it was 1950.

Ben: Okay.

Scott: So after - after World War II they were still producing motorcycles just for a short time and then they went out of business. But early on, they were banned from competition because they had this advantage.

Ben: And this - this technology, as you said earlier, is - is pretty widespread, still. Right? It's a -

Scott: Yeah.

Ben: It was in power tools, you said?

Scott: I'll tell you it's in power tools. It's in snowmobiles. A lot of people know this from snowmobiles. It's from tractors.

Ben: Okay.

Scott: Drill presses, again, motorcycles. I think there's probably other applications of this. We're just not seeing them here. But it's - it's really kinda cool. I'll just give a super basic description of what it is. It's two pulleys that have cone shapes to the inside edge of those - of those pulleys. And they're, of course, positioned right next to each other. The belt runs between them. The belt always remains at the same tension. It never gets slack. It never gets tighter.

Ben: Okay. Yeah.Scott And when - when speeds go up, one of the sets of pulleys expands and - and the belt rides down further in that - in that groove. And it goes higher up on the groove in the other pulley - set of pulleys.

Ben: Huh.

Scott: So it's this kinda seesaw back and forth motion, so at higher speeds, the pulley - on one set of pulleys, it will be riding deeper into that groove, that V-shaped groove that the pulley creates. And on the other set of pulleys, then it will always be at the top end. And I don't mean always, but if it's low on one end, it's high on the other end.

Ben: Right.

Scott: And then, it - it balances itself out, and it just goes back and forth between the two.

Ben: So there's a - there's something here that - that kinda presents a question to us, or heavily implies this question. If this technology has been around for so long, is it the norm?

Scott: It is becoming the norm. And that is evident in that there are some manufacturers that now will offer only manual transmission or a CVT. You can't' get an automatic transmission in some models, not that the manufacturer doesn't offer an automatic transmission, but that's the - that's your option. You either get a manual transmission, a six-speed standard shift, or you get a CVT. And -

Ben: Now we -

Scott: Oh, go ahead.

Ben: Well, I was just gonna - I was just gonna say with the reference to the manufacturer in the Netherlands, is this technology more common in one car market than the other, like Japan or Europe or anything?

Scott: Actually, not. And as far as I can tell right now, and I - I couldn't say for certain whether there are more cars on the road with CVT in - in Europe or in Japan or wherever. I can tell you, though, that since - well, let's - I guess I can just start right here at the beginning. In 1989, there was one vehicle sold here in the United States that had a CVT. And that was -

Ben: Just the one?

Scott: Just the one that was in 1989, the Subaru Justy GL, and it just never took off, never - never really gained any popularity. And I don't know if it had anything to do with the CVT or not. I couldn't say. It's just -

Ben: It could have been any of a number of factors.

Scott: Exactly. Exactly. Now you've got companies like Nissan and their supplier, Jackho, who makes their CVT. That's their transmission supplier. They, to date, have sold over one million CVT-equipped vehicles, so you can see that they're everywhere.

Ben: Yeah.

Scott: They're populating - populating all of the continents, I guess. It's not just Nissan. It's GM, its Audi, it's Honda, Nissan, Chrysler. They're all getting into the CVT game relatively recently, I mean, in the last few years. But Nissan's really been kinda leading the way with this one. I wouldn't say that they were first, of course. They weren't. But right now, they may be the ones doing it the best.

Ben: I've gotta ask one - one other thing here that we - we actually - we did not - we did not talk about earlier. But what - what do you think makes this technology advantageous or disadvantageous, in comparison to an automatic transmission?

Scott: Well, it's - it's got a smoothness to it that automatics do not have because even in an automatic -

Ben: You can feel that shift.

Scott: Yeah, you still have step gears.

Ben: Yeah.

Scott: Yeah. You're right. You still feel that. And now, to a lot of people, that's not good. They don't wanna feel that smoothness because it feels like something's wrong. If you've - if you've driven a car before where there's slip in clutch or the gears are going bad or something, you know that slipping feeling. And that's what you get in a CVT-equipped vehicle. When you - when you step on the gas at - at a light, you'll hear the engine kinda spool up, the revs will go up, but the car doesn't really go anywhere. It slowly accelerates. It doesn't - it doesn't match the way that it feels like it should or that we're accustomed to it happening. So what - what's happening, though, is it's searching for the right ratio in order to take off. And then, it maintains that proper ratio throughout that whole drive cycle. So it feels really odd and it's extremely smooth, and to some people, that just doesn't feel right. Other people kinda blissfully unaware don't even - don't even know that they have the CVT and everything is just fine. They don't really care.

Ben: What do you see as the future of CVTs?

Scott: Oh, you know what? I've been thinking about this one because I knew you were gonna ask me this.

Ben: Yes. Yes.

Scott: I think - and honestly, you know what? I'm surprised at the way - I just can't believe the technology already that we have. It's pretty amazing. It really is when you - when you look at some of the details of these transmissions and what they can do and what they're capable of. They save fuel. They're extremely smooth. They're very - they're very simple, really, inside. There's not - it's not nearly as complex as a standard automatic transmission. What I would say? Future developments I can only guess, but I'm saying further simplification, maybe.

Ben: Okay.

Scott: Just refinement of what's already there if it can be further simplified. I don't even know if it can at this point, but never say never. And I'd also say further weight reduction because weight reduction is -

Ben: It's key.

Scott: - is so key right now. It's very key. I mean, it's critical when you're talking about downsizing engine sizes and vehicle weights. And this is all part of it. The transmission has to be reduced as well. Every little bit counts. So I would say further weight reduction is important and I guess use of new materials. I can only think that that would help in weight reduction and not so much simplification, but new materials might be one way to go.

Ben: It's kinda - in these - in these episodes I've noticed we're reaching toward this - some of the same recommendations again and again. And those are better materials, higher efficiency, less weight.

Scott: Yeah.

Ben: And you know what? Now that we think about it, maybe sometime in the future, we could - we could go - we could go a little bit deeper into that.

Scott: Sure. Yeah.

Ben: I mean, I'm just on a tangent.

Scott: No. All three are tied together. And the new materials tend to be lighter. The - of course, that's weight savings,

and weight savings increases efficiencyBen: Hey, Scott, are we - are we wrapping up on transmissions? You feel like it?

Scott: You know what? I do. I'm sure there's plenty of questions out there, so have at it. Ask me - ask me what you like. And, oh, also, let's just say go to the site, our website,, and check out the article, How CVTs Work, and that will clear up a lot of questions because if you do have questions, there are charts, graphs, advantages, disadvantages, a lot of - a lot of explanation that we just couldn't go into here. And I also have - I urge you to go online and - and there's a lot of animations of CVTs in action.

Ben: Uh-huh.

Scott: And that will clear up a lot of questions you have as well. I've watched many of these over, I don't know, the years, I guess. And to me, that just - just being able to see it in action, that really - it makes perfect sense to you once you watch it.

Ben: Okay, everybody. You heard it here first, hopefully, about how CVTs work, and as Scott has pointed out, you should definitely check out the information on the website. While you're there, you should probably check out his blog. Scott, I don't want to embarrass you, but that story about the Ferrari crash is pretty awesome.

Scott: Yeah. Yeah. There's some - there's some disturbing news about a classic Ferrari, so you might wanna check that one out.

Ben: Yeah. And there - there's always something on that blog that is just utterly fascinating. And if you have any questions, comments, or suggestions for a future episode, please do send us an email at High Speed Stuff at

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