CVTs worth a dang?


#1

So, I’m starting to think about thinking about someday in the next decade or so maybe kinda thinking about replacing the plastic saturn I have. I’ve heard CVTs offer decent mileage. Are they reliable? Powerful? Or does the RPM get kinda locked down in the 1000s?? CVT geeks, pile on, here!!


#2

THEY ?
Too broad of a term as many different CVTs exist.
The one on my 06 Escape hybrid is excelent.


#3

The one in my 15 Forester is very good. I get 30-35 MPG on a trip, 20-30 in the city. It has a few problems, but those are software issues. For example, it sets too low an RPM at low speeds (20-30 MPH) and at 1200 RPM, the engine tends to lug. But a bit more throttle usually solves this.

interesting to drive under cruise control, say at a fixed 70 MPH and watch the RPMs go up on an up hill and VV on a down hill.

The other issue is: if you are driving at, say, 30 MPH and need sudden speed and floor the throttle, there is a noticeable lag before the CVT gets to the correct ratio. I attribute this to the fact that the chain has to slice all the way from one end to the other, whereas an ordinary automatic just has one gear shift to do.


#4

Only way to tell is to drive one. My MKZ has a ‘CVT’, by way of two electric motors, a gas motor, and a gearbox (like the Escape). Non-hybrid CVTs are usually the cones and belt variety, which have been improving. As for reliability, not as good as some of the older auto trannys, but these days if they’re not being replaced by a CVT it’s by a 6/7/8/9 speed AT with unknown reliability.


#5

My wife has a Nissan Sentra with a CVT transmission. I did not like them but it’s the car she wanted. Funny thing…her little car could go anywhere in the snow (8 inch snow fall) and ice with just “all-season” tires (bought new in the late fall). I now have a new found respect for CVT transmissions and she gets great gas mileage. I would never have bought one but my wife took a chance and it seems to be paying off for her.


#6

I was provided with a Nissan Sentra for a road trip to and from a conference which was a 600 mile round trip. The Sentra had the CVT. It seemed a strange at first, but after a few minutes, neither me nor my research associate thought anything about it. The only thing that bugged us about the Sentra was,that the dash lights were too bright and we didn’t think there was anyway to dim them. Later, after the trip was over, I learned that you twist the button that when pushed in, resets the trip odometer.
In some ways, the CVT takes me back 65 years,to the Chevrolet PowerGlide and Buick Dynaflow transmissions that didn’t shift, but depended completely on the torque converter for torque multiplication. The GM Hydramatic which was available on the other GM cars as well as the Nash, Kaiser, Hudson and Lincoln(yes, Ford bought transmissions from GM) were 4 speed units with a fluid coupling instead of a torque converter. The PowerGlide and Dynaflow were smooth, but had a lot of slippage. The Hydramatic had much less slippage but was jerky. Today, the CVT doesn’t slip and the gear changes,on the multispeed transmissions are very smooth. I think whether a car has,the CVT. or the multispeed transmission probably doesn’t make much difference.
One. comment I read about the PowerGlide and Dynaflow transmissions was that Chevrolet and Buick used these transmissions because both the Chevrolet and Buicks had enclosed driveshafts and the Hydramatic with its jerky shifting would have the.jerkiness amplified by the torque tube driveshaft. The other GM cars had open driveshafts. I don’t quite believe this because Nash and Rambler used the GM Hydramatic from 1950 through 1957 and these cars,had torque tube driveshafts. I have ridden in and driven Ramblers of this time period and the transmission shifts weren’t any worse than the GM cars. I probably could have gotten used to either automatic transmission, but in the family in which I grew up if you couldn’t shift gears, you wouldn’t be driving.


#7

“Ford bought transmissions from GM”

That scenario still plays out

In the world of big trucks, for the most part, there are really one 2 major choices

Eaton-Fuller manual transmission, and lately, automated manual

Allison automatic transmission, made by GM

As far as I know, many of the Ford big trucks even now use an Allison

By big, I don’t mean pickup trucks. I mean class 7 and 8


#8

Ford doesn’t maker class 7 and 8 trucks anymore. Of course neither does GM or Chrysler.


#9

:frowning:


#10

@triedaq, frictional CVTs slip all the time because the belt that meshes with the cone has finite thickness and it travels linearly before it wraps around and rotate with the cone. The part of the cone that meshes with the belt rotates and the inner edge turns slower. Since the inner part of the belt is traveling linearly with the outer edge and the inner edge of the cone is slower than the outer edge, you have differential slip

Unless someone makes a feasible business case on ratcheting CVT, my money is on automated manual.


#11

But Allison is still very much in business’s.


#12

A transmission shop near me LOVES CVT transmissions. Repairs them weekly.


#13

oldtimer

looks like Ford is still building a class 8 truck

http://www.fleet.ford.com/fleet-showroom/?brand=Ford&md=F-650-750&yr=2016&sg=commercial-trucks&selected=capability

According to my sources, 37000lbs GVWR is considered class 8


#14

CVTs would have to have a ten year record of reliability comparably to automatics (which are excellent) before I’d consider getting one. Everything I’ve read about them so far suggests that more development needs to be done.


#15

“the belt that meshes with the cone”

That may be true for some CVTs, but I can tell you that Subaru’s CVT uses a wide roller chain.
I believe that there are others that also utilize a chain instead of a belt, but I have to plead ignorance of which ones these might be.


#16

Here’s Subaru’s video of its CVT in action:
https://youtube.com/watch?feature=player_embedded&v=p14iUl5YH3E

Notice they still have a torque converter. The CVT lets the engine run at optimal rpm. I’m betting they are cheaper to make than a 6/7/8 speed AT.


#17

GM doesn’t own Allison Transmission anymore, probably why Ford buys from them. They sold to Carlysle Group and ONEX in 2007 and it went public in 2012 and YOU can own stock under ALSN if you wish.

CVT’s have been sold in cars for over 50 years. Remember the DAF Daffodil? Had a Variomatic CVT developed in 1958. Honda introduced one in the Civic in '95, Nissan in '92 and they switched over wholesale by '06. Audi in 2000, GM in '02, Ford in '05, Chrysler in '07. Many have died horrible deaths. Others, like the Nissans, seem to be going strong. Don’t own one but I’m curious like the OP.


#18

@Mustangman

Ford installed Allison transmissions back in the day, when GM still owned them. In the 1990s for sure.

Up until recently, we had a 1997 F800 or something along those lines in fleet. It had a non-Ford diesel engine . . . Cummins, I believe . . . and it had an Allison 3000 series automatic transmission. The hilarious thing was that the service information referred to a Ford diesel engine and a Ford automatic transmission. I guess they didn’t want the purchaser to know the drivetrain wasn’t Ford


#19

That roller chain does not mesh with a sprocket. It is clamped by four cones. There are advantages to using a chain as opposed to a push belt. It can do smaller radius so the ratio spread can be higher. It requires a somewhat lower clamping pressure. Speaking of which, it requires clamping pressure because the clamping provides the friction for force transmission, not the interference between roller and sprocket. And just as in a belt CVT, it has differential slip.


#20

It seems to me that the Japanese preferred the smoothness of CVT despite their disadvantages. Even if they are reliable, they have yet to match the ratio spread of modern multiple speeds automatics. They probably don’t pile on enough mileage to see them fail like the Americans and Europeans do.

Europeans are more familiar with manuals and are more comfortable with automated manuals direct response. Audi tried their hands with CVT before they returned to dual clutch automatics. Many small cars have automated manuals.

When I was a part time motorcoach driver in California, some preferred the ZF 10 speed automated manual while others preferred the old school 6 speed Allison.