In the thread on cam belts and chains Screwloose was very pessimistic about CVT suggesting you could go through two gearboxes in 30k miles
I said
Bit surprised to hear what Screwloose has to say about CVT. I thought the Merc A and B class autos were Autotronic CVT's and don't recall negative feedback.
Also hear that the Nissan owned JATCO plant in Mexico is tooling up to produce 800,000 CVT boxes this year.
Where's the problem or weakness?
Cheers. >>
Any takers?
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The weakness is that they just don't work. Ford's CVT was a disaster - as was Fiat's identical Speedgear [or whatever it was called] due to premature wear of the drive components. Just ask any autobox repairer.
Production was delayed about 20 years from announcement; [I've a feeling that it was Van Doorne that held the rights?] to try and get the durability of that steel-block belt up - without obvious success.
No-one is going to pay the thick end of £2000 for yet another gearbox on a 6 year-old Fiesta - let alone a Punto.
As for negative views on an A-Class - I've never heard a good word. They redefined awful.
Given Renault-Nissan's recent track record; I'm not surprised that they are going CVT - one more problem to deny won't make any difference.
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The CVT as used automotively has to contain elements which both roll and grip. This applies whether the operating principle is that of the swashplate roller drive (Perbury) or a belt fitted to expanding pullies (DAF et al).
So, what are you asking the lubricant to do - slip (as in allowing the belt to shuffle around on the pulley flange) or grip (as in transmitting the input torque to the load). Slip (as in allowing the Perbury rollers to shift on the camplate) or grip (as in doing some useful torque transmission).
I'm not surprised they don't work. Little ones have been used fairly sucessfully for alternator drives on military vehicles and the like but the prospect of transmitting meaningful torque through a device the size of a car gearbox given the ravages of everyday driving does not fill me with enthusiasm.
A sign of a marginal design is the need for special lubricants. These gearboxes have had a sucession of special oils made for them - no hope, I'm afraid.
659.
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Anyone had any problems with the CVT in the Honda Jazz. Would have considered one when the trusty yaris is no longer.
Mark
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Did they have that much trouble with 1990's Micra CVT then?
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The negatives on here do seem very negative.
I can't see the point of the lubricant argument. As far as I know, CVT's use a modified auto transmission fluid. What's so unusual about auto transmission fluid or indeed about new, improved lubricants?
The readers' reviews in a car magazine, what name I'd better not mention, of the A and B class Mercedes with auto are positive. As are those of the Qashqai CVT. And Nissan have just brought out their 2009 Maxima in the US: a 3.5 litre with Xtronic CVT.
Hopefully these new CVT's won't turn out to be the DMF's and DPF's of the future.
I can still remember my dad rejecting an automatic car when I was a kid on the grounds that they wouldn't work properly!
Edited by Optimist on 16/06/2008 at 18:49
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I have a 2002 A4 with a CVT. Don't do many miles these days but at 44k it has not been a problem. An oil change at 34k did improve the smoothness.
It is a petrol 2 litre so not too much torque, and because of the perceived history of problems I do drive it carefully. It has the original 6 plate clutch rather than the later 7 plate.
I love this car. Please don't make it a hypocondriac by writing nasty things about its internals.
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No trouble with a CVT Punto I had for some 40K miles from 2001. I am not sure how such gears work but they should be simpler than normal auto boxes and I would expect fewer troubles.
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they should be simpler than normal auto boxes and I would expect fewer troubles.
Heh, heh, heh....
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No, not really. As someone said above, with a petrol a CVT is fine. The Qashqai uses a "conventional" auto with the diesel 2.0. Which has the DPF, as it happens. The 1.5 diesel doesn't and doesn't have an auto option either. The Qashqai CVT is the petrol 2.0.
The problematic Ford allies a diesel to a CVT. Maybe they just don't get on. Belts may seem a funny way of transmitting power but are we really saying that two spinning discs brought together isn't?
Cheers.
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CVT and reliability do not belong in the same sentence.
An older model, but we had a 95N Volvo 440 2.0 with CVT (High Tech Automatic as it was marketed) The gearbox ruined a perfectly good car. If you didn't brake in the "correct" manner the engine used to stall. We no doubt got a good deal on it when we bought it because of the CVT. I actually wrote to the original owner/purchaser of the car and the gearbox problems were the reason he got rid despite remedial work by Volvo. Had the car been a manual or traditional auto it would have no doubt been more expensive, it was faultless in all other respects.
We chopped it in against a Toyota RAV4 at the time. We were also considering the Honda HRV but decided against it because it too was a CVT.
Never again.
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I remember posting on this subject several months ago. I made the point then that if CVT is so unreliable, shouldn't we all buy torque converter gearboxes (if we want an automatic, of course).
To that end - I asked the question then and I'll ask it again now - where can we find a list of gearboxes (cars) showing which have CVT and which have torque converter automatic gearboxes.
What Car - and similar magazines - simply show them all as automatic, without any subdivision.
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It's even more complex than you think, drbe. I seem to recall from HJ's review of the Nissan Qashqai that the CVT has a small torque converter to ensure the take-up of power is smooth and you get a "creep" in traffic. It's the internal machanics that makes the difference between the CVT and the more conventional auto box. They're both pretty complex set-ups, after all.
Screwloose seems so knowledgable about motors that I would rarely want to disagree with him. But I'll be interested to see how the 800,000 CVT boxes JATCO is producing this year do go.
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It's meaningless to say a gearbox is ok after 40k miles.
It should last 100k miles and 10 years plus.
Given what I know of the manufactruing problems and the inability og garages to change the oil and replace it with the correct one, I''ll stay away.
No £3,000 car is worth buying if gearboxes go and cost £4,000.
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Mobylette seemed to have it sussed years ago.
One pair of moving pulleys, and an engine swinging against a spring for belt tension.
An external belt, and 50cc coped with sixteen stone and puddles (as long as the splash guard was in place) ;>)
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Yes, I hired an Oriental thing of that sort in a small African capital once, cheap and handy way of getting around there being no traffic to speak of. It was fully automatic and 2-stroke. Some people used to start the engine by putting the thing on its stand, pedalling furiously and then doing whatever you did to let the clutch in, then dropping it on the road and wobbling off. I found it easier to pedal the whole thing down the road like a pushbike. The acceleration was better like that :o}. People used to sit by the road selling petrol premix from old wine bottles, or Winchester jars for bigger vehicles. Its transmission belts got twisted once when I was on the way somewhere, but a kind passer-by familiar with the things rolled up the sleeves of his immaculate white robe and dealt with it, refusing all payment. Ordinary Muslims are good people when not messed around.
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CVT's are more efficient than torque converter boxes, which compensates for their problems.
I wanted a C-Max - the auto choices were 2 litre petrol torque converter - 25mpg on urban cycle - or CVT diesel - 40mpg on urban cycle. Over 40,000 miles that's 600 gallons less - or £2000 plus at current prices. The diesel car tax will be £200 a year cheaper than the petrol next year too.
I've got an aftermarket warranty that includes the gearbox - that costs £300 a year. I'll keep the car a long time and look after it - changing the oil more frequently than Ford recommends. And I'll go on enjoying the super smooth power delivery and near-manual performance advantages of CVT.
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