Pros and Cons of a CVT?

Duke wrote: I have never - and I mean *never* - driven a CVT that I liked. I actually prefer to feel the up and down shifts to the rubbery, lazy action that most CVTs seem to have.

For a toaster, really, it does not matter. However, the rubbery, lazy action pretty much describes it. The wife has a Versa and I did test drive the Scion IQ, both feel like acceleration is via a pulled rubber band; lots of throttle modulation to find a steady state cruise.

The Versa is going on 10 months now, and I have to say I notice it less, but also comment on how it totally tranquilizes me while driving. I never feel like pushing that car. And that fine with the wife unit.

the new accords have a cvt and i'd say it drives a lot better than any others ive driven, even feels..."sporty"

belteshazzar wrote:

carguy123 wrote: Every CVT I've driven has been in the "emulate X# gears like an automatic" mode.

this bothers me more than any other aspect. BE YOURSELF TRANNY!!!

This is wrong on multiple levels.

I'd love to try a CVT in a car. That is a CVT that's acting like a CVT. I like the concept, but have no idea if I'd like the execution.

I have the CVT on my '08 Patriot and it doesn't bother me at all. In fact, I really like it. I think I have about 60k on it so far. I may look into the trans oil change though as was recommended here. Try it out for yourself to see if you like it honestly. There seems to be some noise on your thread, so real-world experience might be more advisable.

-Hamid

SyntheticBlinkerFluid wrote: I want to know reliability, cost to repair, ease of maintenance, etc.

That's about like asking "what's the reliability of automatic transmissions?" There's far too many of them to make a blanket statement.

My own automotive CV transmission experience has been with Hondas and Toyotas. We've got a fleet of Hondas here at work, all with 120k-160k miles on them, and as far as I know, not a one has been in for transmission work. The Toyotas I know have less miles, but none have been in for transmission work either.

As for sucks to drive, and the comments about attempting to emulate a geared transmission, I'd disagree with both. I've never driven/ridden one that behaved anything but like a CV transmission. No shifting points, they all fully exploited the benefits of being continuously variable. With the cars, the engine would be placed in maximum fuel mileage range for steady cruising, and brought to peak power rpm when floored, and somewhere in between for other conditions. Again, since there was/is no lurching and no changes in engine rpm, you don't feel like you're accelerating. It's very smooth and subtle.

Anybody here have experience with the Subaru Justy CVT? IIRC that one was a true CVT.

I hated every one I've used, but I know that's not the feedback you are looking for. I also know it's not totally apples to apples, but the Altima I rented once for 1k miles had a 4 cylinder with the CVT. It got 30 mpg on my trip, all highway. My Acura TL-S, a heavier car with a much more powerful V-6 and a 4 speed auto, routinely got 31mpg in the same conditions. What's the benefit of the CVT again?? Now, I do hear that the CVT in the new Accord is supposed to be the best ever in regards to driving satisfaction, but I've not driven one myself.
Theoretically, they should improve fuel mileage, but so far I haven't experienced that in any of the 3 that I've driven, and coupled with the total lack of driving satisfaction, I won't be buying one any time soon.

carguy123 wrote: Every CVT I've driven has been in the "emulate X# gears like an automatic" mode. My daughter has a Nissan and she couldn't even find someone to tell her how to put it into the real CVT mode.

Simply put it in "D". It will only emulate a regular transmission in manual shift mode (paddles or move the shifter to the side on some models) or if it's in "Sport" mode.

Curmudgeon wrote: I had occasion to send a used car to our Nissan dealer for a CVT repair (same JATCO transmission), Nissan specifically states the fluid MUST be changed at 60K to keep the warranty in effect. We are not to try to repair a CVT in the shop under warranty, we get a complete unit. There's a final drive? bearing which can be replaced but that's about it.

Not true, the Nissan manual simply states the fluid deterioration date should be checked every 96,000kms (about 60k miles). This is done with a scan tool, the fluid should be changed once the number reaches 210,000. I was in training last week and the Western Canada Nissan trainer said he's never seen one reach that number, the closest was 209,000.
There is a bulletin for the 07-12 Altima for diff bearing replacement.
Speaking of failures, the Nissan trainer quoted the CVT failure rate was at about 1% if ignoring a rash of Rogue transmissions in 2008 and 2009 (Half of those were not even bad, there is a recall with a reprogramming to fix the problem, which was simply a noise on de-acceleration).

Another thing to note is that NIssan warranty's CVT for 10 years/200,000kms (120k mi).

Now I'm not saying I like them and how they drive, but there's a lot of mis-information in this thread. If I were looking for an appliance family car, the CVT wouldn't have any bearing on my decision.

Anybody got a link to a diagram/drawing of an automotive CVT? I have a good understanding of scooter CVTs and they don't require fluid (except in the final drive). If there is a fluid inside the CVT, I'd assume it is there as a friction modifier and coolant, but would effect efficiency negatively.

In reply to Run_Away:

I'm aware of Nissan's 10/120 warranty on the CVT's, the one I sent to our local dealer was a warranty situation. As it turned out, after speaking with the advisor and manager, the transmission was warrantied only because the owner, in an attempt to 'fix' the transmission, had the fluid changed at 64,000 miles. The car had ~ 69,000 miles at the time of repair, IIRC.

Run_Away wrote: Simply put it in "D". It will only emulate a regular transmission in manual shift mode (paddles or move the shifter to the side on some models) or if it's in "Sport" mode.

I wish it were that simple. Apparently there are 2 modes the transmission can be in and it comes set from the factory in the emulation mode.

carguy123 wrote:

Run_Away wrote: Simply put it in "D". It will only emulate a regular transmission in manual shift mode (paddles or move the shifter to the side on some models) or if it's in "Sport" mode.

I wish it were that simple. Apparently there are 2 modes the transmission can be in and it comes set from the factory in the emulation mode.

That's car specific. That's not for all CV transmissions. None of the ones I've operated in automobiles behaved this way.

RossD wrote:

Curmudgeon wrote: As far as how they drive, it's weird but lots of people get used to it. AFAIK there is no 'approved' way to put Chrysler versions in any mode other than the factory programmed A/T emulation mode.

As an engineer and a car guy, that part made me pissed. Is there a production CVT that doesn't use friction as the power transmission means? (i.e. a gear) Friction style CVTs work great on slippery applications (snowmobiles...) but I just foresee lot of wear in the high mileage units... I don't know if this is really the case, however.

Any drive train, manual, automatic, CVT all work on friction.

iceracer wrote: Any drive train, manual, automatic, CVT all work on friction.

Care to clarify?

It seems like the question was about the distinction between a CVT, which uses a constantly moving/rolling friction contact to transfer all power, while a manual transmission with the clutch pedal out should have no relative motion at the friction point (clutch) at all, and more to the central point, all its gear-ratio paths are via toothed gears which do not rely on friction to transfer power.

Curmudgeon wrote: In reply to Run_Away: I'm aware of Nissan's 10/120 warranty on the CVT's, the one I sent to our local dealer was a warranty situation. As it turned out, after speaking with the advisor and manager, the transmission was warrantied only because the owner, in an attempt to 'fix' the transmission, had the fluid changed at 64,000 miles. The car had ~ 69,000 miles at the time of repair, IIRC.

Then I would say that particular dealership was being less than honest. Nowhere in any Nissan litterature does it state the fluid must be changed at X mileage, simply "inspected" via scan tool. This is for both for normal and severe use maintenance schedules.

carguy123 wrote:

Run_Away wrote: Simply put it in "D". It will only emulate a regular transmission in manual shift mode (paddles or move the shifter to the side on some models) or if it's in "Sport" mode.

I wish it were that simple. Apparently there are 2 modes the transmission can be in and it comes set from the factory in the emulation mode.

What type of Nissan? In my 4 years as a Nissan tech I've never come across this. The only CVT settings adjustible with a dealership-level scan tool I've found is the amount of engine braking allowed.

ransom wrote:

iceracer wrote: Any drive train, manual, automatic, CVT all work on friction.

Care to clarify? It seems like the question was about the distinction between a CVT, which uses a constantly moving/rolling friction contact to transfer all power, while a manual transmission with the clutch pedal out should have no relative motion at the friction point (clutch) at all, and more to the central point, all its gear-ratio paths are via toothed gears which do not rely on friction to transfer power.

Friction is what allows power to be transferred through through a clutch disk( manual) , clutch packs ( auto) , and belts.

Manual transmissions rely on friction for synchros to match speeds every time you shift even if the power is transferred through gear teeth once engaged.

A properly operating CVT should not have any slippage between the "belt" and the variable sheaves. Slippage generates heat, robbing power, and shortening life which is detrimental.

Unlike a scooter or snowmobile that pulls on a rubber/fiber belt, one version of automotive CVT pushes on the metal linked belt. The automotive version used hydraulics to control the sheaves rather than relying on springs and weights like a snowmobile.

How stuff works has a good primer on CVTs if you want to see more on the styles out there.

Run_Away wrote: What type of Nissan? In my 4 years as a Nissan tech I've never come across this. The only CVT settings adjustible with a dealership-level scan tool I've found is the amount of engine braking allowed.

I waited till my daughter got here so I could drive hers again and refresh my memory. My memory is right it came from the factory in some sort of emulation mode and it shifts like it has gears even tho it's a CVT. We checked that too.

Hers is an '08 Altima with the 4 cylinder.

BTW her boyfriend has the same model car only with the 6 cylinder and they say his turning radius is a lot wider than hers. Is that possible?

carguy123 wrote:

Run_Away wrote: What type of Nissan? In my 4 years as a Nissan tech I've never come across this. The only CVT settings adjustible with a dealership-level scan tool I've found is the amount of engine braking allowed.

I waited till my daughter got here so I could drive hers again and refresh my memory. My memory is right it came from the factory in some sort of emulation mode and it shifts like it has gears even tho it's a CVT. We checked that too. Hers is an '08 Altima with the 4 cylinder. BTW her boyfriend has the same model car only with the 6 cylinder and they say his turning radius is a lot wider than hers. Is that possible?

Alright, well I'll keep an eye out for that and ask my instructor next time I'm in for training. I've never seen that before.

As for the turning radius, I don't have the service manual here at home but the online parts catalogue shows the same part number for both 4cyl and V6 Altimas (I'm assuming both are sedans?) so it should be the same unless the knuckle is different.

Before you purchase one, go to a transmission shop and ask how much a rebuild is. One of three things will happen: either you'll pass out after hearing their estimate, they'll tell you that they can't do it (some aren't even really rebuildable since there aren't parts for them), or they'll just say "buy a used one."

After having run transmission shops for so many years, I pretty much vowed to never have another automatic. A CVT (from my end of the business) is even worse. Expensive, poor track record, poor parts availability for most, extreme lack of experienced rebuilders.... I would run - FAST.

carguy123 wrote: Every CVT I've driven has been in the "emulate X# gears like an automatic" mode. *snip*

I find it ridiculous that manufactures choose to make a CVT "act" like a regular auto trans. There must be lots of complaints about driving regular CVTs for them to do this.

And doing some noodling at work I find that a CVT is not much more expensive than a regular auto trans.