My Insight’s CVT is doing fine, but I’ve only just passed 50K on it. I had high hopes for the dual-clutch designs; however, (except for the Porsches and Ferraris) they’re also having teething problems.
And lets not forget the Buick Dynaflow which was introduced in the late 1940s. It had a 5 element torque converter which provided a variable ratio with no gear shifting. It was probably the first CVT. A slush box if ever there was one.
Tell me more about the Buick Dynaflow. In 1962 I was in 8th grade and had a fresh science teacher just out of school. He had just bought a new Buick and he said the reason was that it didn’t shift and was or was like a CVT. Some claimed that wasn’t true, but I saw it and watched drive and he was no slouch. Had researched all the cars before he bought.
As far as replacing instead of fixing is concerned, I would venture to say except for the linkage and actuators, most transmissions, regardless of their makeup are replaced and not fixed at dealerships. At least in this area, the several transmission shops we had have gone by the wayside as they have increased in complexity and changed. The usual independent isn’t going to touch them and now it’s back to a dealer whom…will replace instead of fix. How different is it where you are ? Until transmissions are replaced by electric drive motors, transmissions including CVTs are pretty specialized. I found out for a lot of items that it isn’t just the complexity of the units, but the inter connectivity where removing and replacing a simple part on or in a transmission requires you move or remove so many other drive train components, replacement becomes less expensive.
Heck, there are some dealerships that have trouble dealing with simple starting problems on a car under warranty. Are you Going to trust them to remove and fix a transmission ? I don’t think even the manufacturer does. I can’t speak for an Insight , but the Prius CVT is not I believe the typical belt unit used in regular cars.
“the Prius CVT is not I believe the typical belt unit used in regular cars”
Are car makers actually still using belts in their CVTs?
I know that Subaru uses a wide steel roller chain, and I would be very surprised if the other car makers weren’t also using chains at this point.
Be it a chain or belt, they aren’t positive drive transmissions. The belt or chain are still clamped between four cones to transmit power and they slip all the time. Not to mention the power required to operate the high pressure pump that keeps the belt or chain clamped and negating any efficiency gain. I have no problem with CVT if they are positive drive mechanisms. Otherwise, I ain’t buying it.
The Buick Dynaflow had a two speed planetary gear box with a multielement torque converter. The 2 speed was essentially a Powerglide design without the automatic shift valve body. The gear selector was placed in Drive or Low depending on the need for extra torque or engine braking.
The multielement torque converter worked as follows. The engine drove the pump which was on the rear side of the TQ encloser. A stub nose also drove the line pressure pump which engaged the multidisc clutch for direct or the band for low gears in the box. The TQ pump slung oil to the outside of the enclosure. This oil first encountered the 1st turbine blades. Pressure imparted to this element drove a ring gear at the center of the 2nd turbine. The ring gear rotated against planet gears with the sun gear held stationary by a roller one way clutch. The planet cage was connected to the 2nd turbine hub and drove the gear box input shaft as did the 2nd turbine. After the oil left the 1st turbine blades, stator #1 redirected the oil to enter the 2nd turbine to also push it along. The oil exiting from the 2nd turbine was rediricted by stator #2 (lower stator) to enter the pump vanes in a forward direction so the pump could reenergize the oil flow without turbulance.
As the input shaft gained speed, the 1st turbine would begin to overrun the planets so the sun roller clutch would freewheel. The stator #1 following the 1st turbine would also freewheel on its oneway clutch. Now the unit worked as a regular TQ with pump oil applying force to the second turbine and oil being redirected by the lower stator #2 back into the pump. As the 2nd turbine rotated faster, the lower stator #2 would also freewheel on its oneway clutch and the TQ now would act as a fluid coupling.
The only disadvantage of this TQ was its lack of lockup clutch. These transmissions were usually behind a 322 CI or larger V8 engine. As fuel economy and efficiency were not demanded they worked fairly well. About the only time you needed Low was on the hills in San Francisco. In the years I drove a 1956 Buick Special, I never had a problem with the transmission. I did have to replace the rear pumpkin and drive shaft as a the splines wore off against eachother. It had a torque tube with only a front U joint. Thisbeast had manual steering and standard drum brakes. Maneuvering and stoping was a hand full but once it got rolling on Interstate 5 it was a cruising dream.
The other transmission with a multielement TQ of this ilk was the Turboglide, also termed the terribleglide.
@researcher–I had a 1954 Buick, but it had a 3 speed manual transmission. In 1955, Buick had a “switch the pitch” feature in the automatic transmission which gave the Buick better acceleration over the earlier manual transmissions. Your 1956 Buick, I think, had a 352 cubic inch engine which was standard throughout the entire Buick line. However, upscale models had higher horsepower ratings.
One interesting note–the Studebaker automatic transmission, introduced in 1951 did have a lockup torque converter.
Don’t get me started on the Buicks of the 1950s. I really liked the cars, torque tube drive, lever action shocks and all. I think, however, that Buick went to regular shocks all around in 1956. My 1954 had the regular shocks in front, but lever action shocks which could be refilled in the back.
I think that the best looking Buick of the 1950s was the 1957.
“The belt or chain are still clamped between four cones to transmit power and they slip all the time.”
I don’t think they slip (the friction cones would wear out quickly if they did), but there is internal friction in the steel belts. In this sense, meshing gear teeth also have slipping surfaces between them. I’d be interested in any data that shows the input/output ratio can change without the cones moving axially.
The automakers use CVTs for one reason- Better EPA fuel economy. Most owners don’t get the bettwr fuel economy because it feels like the car isn’t accelerating fast enough so you step harder on the gas.
Same problem with using a smaller engine with a turbo to get good fuel numbers. You only get them if you accelerate slowly enough to not use the extra power the turbo will give you.
There is no free lunch. More transmission speeds will deliver more fuel economy but they make the tranny heavier or more fragile (take your choice) and are more expensive.
I’ve never driven a car with a CVT that I liked. I once rented a Dodge Caliber on ski trip out west. Appalling car in just about every way. It only had 300 miles on the clock when I rented it, and it rattled and squeaked worse than my (at the time ) 12 year old Bronco. It was so underpowered that you really had to stand on the gas to get any real semblance of forward motion, and because it had the CVT, the revs just hung at 5000-6000 RPM until you eventually reached your desired speed. It was very noisy, which I don’t mind if there’s a nice exhaust/engine note, but this road-going appliance did have that either.
I also sold Nissans and Fords for a time. The Murano’s big claim to fame for a while was that it was the only car sold in the U.S. with a CVT. The Murano to me was a jack of all trades-master of none. It did a lot of things reasonably well, but it wasn’t exceptional in any way, and it was a bit overpriced IMHO. There were several training videos that we watched on how to explain to customers that the whole not-shifting thing was normal and it wasn’t an automatic that was slipping badly. Nissan has gone whole hog with CVT’s though. These days you can get a CVT on most cars in it’s line up. I think the only exceptions are the 370z, Titan, Frontier, GT-R, and Armada.
When the Five Hundred came out, you could get some trim levels with the CVT and some with the 6 speed automatic, which was a rarity at the time. That car never really sold well, as it was bigger than the older Taurus, which was a turn off for some people, and too modern for the traditional Crown Vic buyers, and it if you wanted one all loaded up with leather and everything, it was more expensive than either the Taurus or the Crown Vic. The press didn’t help either, as it was lambasted for being underpowered compared to the V6 Altima, and V6 Accord. Ford’s 3.5L wouldn’t show up until a few years later, and by then Ford gave it the Taurus name for two years until the all new Taurus debuted, when the 3.5L became standard, the CVT went away as it had garnered a less than stellar reputation and more powerful 3.5L V6 produced more power than the CVT was able to handle reliably.
There was a lot of model overlap from around 2005 until around 2010 for Ford.
In the Nissan parts department (and others) they are referred to as belts. They are steel but unlike a chain which connects gear cogs, these "belts ride on pulleys. They are belts in every sense of the word.
subaru cvt transmission diagram
As far as Subaru is concerned, In at least some literature, it is still referred to as a belt.
The CVT in a Prius does not use a belt but a planetary gear set that requires a computer and electronic actuators to constantly vary the ratios. Other non belt heavy duty CVTs include those used in tractors (hydrostatic) transmissions. They are less efficient in some respects ( straight line driving) but more in others ( shuttle use) and very durable and can be used with higher torque motors then those which drive via belts.
@insightful, when you have a belt or chain with a finite thickness going straight trying to engage the cone with different parts have different linear velocity, because they all have different radii, there’s going to be slip. CVTs use a special fluid that temporarily becomes a solid when clamped between the cone and belt or chain and the 2 metal parts don’t make contact, theoretically. But the slip is there. That and the need for a high pressure pump is a deal breaker for me.
"Is a deal breaker…"
I’m sure that was said about the automatic transmission when it first came on the scene.
CVT transmissions have been continuously improved for the last decade now. That being said Nissan, among others is still dealing with CVT issues.It used to be that if your automatic transmission ran low on fluid or got a little contamination in the fluid the transmission would begin to skip or not even move the vehicle at all. You replaced the fluid and/ or just topped it up and away you went. No permanent damage. Not so with a CVT. In Nissan’s factory manual, if the tech hooks up his computer when a customer comes in complaining of transmission related problems the first thing they do its check the sensors for fluid level, temperature and contamination. CVTs are highly susceptible to damage caused by contamination, low fluid, even fluid temperature is critical. You can’t even check fluid level in one unless the fluid is at a very precise temperature. . Oh sure there are other DTCs to check, P0778 Pressure Control Solenoid B, P0863 TCM Communication among others which can be fixed. But if the tech sees a DTC on his screen P17FO CVT Judder (otherwise known as the DTC from the Dark Side), he stops trying to fix it and informs the customer that it has to be replaced. This with as little as 5000 miles on the clock. Nissan had no choice but to increase its warranty to 10/100,000 because of the failure rates in this transmission. All of this to say that this is obviously a flawed design that the manufacturers are putting on the market. Gone are the days of a robust transmission that can take abuse and every little thing doesn’t have to be just so. Why would Nissan and others put out a product they know to be flawed? It’s simple. CVTs have fewer parts, are simpler to manufacture and help with the corporate EPA mileage ratings. But the real reason is its cheaper to make one. If they save a few bucks on each one that translates to millions on the bottom line. Why would anybody buy such a delicate piece of machinery? Because the manufacturers pay advertising guys lots of money to think up a million excuses to make people think CVTs are OK.
Good news Mike! Here I’ve asked a number of dealers about that and they say “we just replace them”
Shops around here still have not geared up yet to rebuild them. I’m sure the day will come.
You’d think a CVT would be relatively simple to rebuild, compared to an 8-speed AT. Wonder how the part count compares…
from what I’ve read, friction cones must be replaced together with a belt or repair does not last
the almighty google was able to find only this:
I’m not sure if original parts can be sourced from dealer
I’ll stick with the automatic transmission over a CVT transmission because of the durability issue. I was thinking about getting a new car, but the CVT knocked all foreign cars out of the running, and then I found out about an idiotic idea called Stop/Start technology with many American cars. But at least, some of those cars will allow me to turn off the Stop/Start system. American cars would begin to rule the foreign cars if they dumped the Stop/Start systems. All of this so-called new technology is enough to make me want to keep my 1999 Mercury Mystique.
Plenty of ‘foreign cars’ that don’t have CVTs, just have to look.