A theoretical question, do the clutches in DCT/PDK wear in same manner as of those in manual transmission cars?
As the load is shared by 2 clutches, does it mean after say 100k miles, individual DCT clutch will wear 50% compared to a manual clutch at same mileage (assuming similar computer logic is used to change gears in manual car).
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DCTs can have wet or dry clutches, so the wear will be different depending on what type of clutch is fitted. What DCT does do is remove the driver from the equation, so the massive factor in determining clutch life in a manual transmission - the driver's treatment of the clutch - is taken out of the equation. A precise, consistent, mechanically sympathetic clutch operation can be guaranteed over an extended period of time, which will improve clutch life. Also, most DCTs auto rev-match on downshifts, which reduces clutch wear to near zero.
There are people reporting 100+k on DCTs used regularly for track days that are still performing fine on their original clutches. That's quite hard to envisage with a manual transmission.
In terms of wear patterns, in theory, the clutch for odd gear numbers will be subject to take up of drive from rest, and so will have a slightly harder time than the clutch for the even gear numbers which will only ever have to deal with gear changes under perfect rev matching conditions.
Evidence suggests DCTs suffer more from software / electronic issues than mechanical wear.
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>> DCTs can have wet or dry clutches, so the wear will be different depending on
>> what type of clutch is fitted. What DCT does do is remove the driver from
>> the equation, so the massive factor in determining clutch life in a manual transmission -
>> the driver's treatment of the clutch - is taken out of the equation. A precise,
>> consistent, mechanically sympathetic clutch operation can be guaranteed over an extended period of time,
I don't think that's true. The manual for our DSG Roomster cautions against "holding the car on the accelerator".
Yet that is how some people drive autos, by using the creep. The only way that can be achieved on a DSG is by slipping the clutch. That will cause wear and generate a lot of heat. If you are unlucky enough to buy a used car formerly owned by someone with that habit, it might well have a short life.
That is the weakness of the design. It is a system for rapid and accurate gear changing originally used on high performance cars that has been adopted, because it is more fuel efficient than a fluid torque converter, for everyday cars.
Huge effort has gone into simulating the driving experience offered by a TC auto, but it is unsuitable to be used in a way that some lifelong auto users are habituated to.
Last edited by: Manatee on Sun 12 Feb 17 at 07:04
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>> Yet that is how some people drive autos, by using the creep. The only way
>> that can be achieved on a DSG is by slipping the clutch.
My manual Roomster will creep quite effectively in traffic in first gear without any need to slip the clutch.
Presumably there is no way of doing that in a DCT version with an assurance the clutch is not being slipped?
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Whether it is slipping or not presumably depends on the load. I was rolling along in traffic in ours on Friday. I used tip mode to keep it in first, it changes into second almost as soon as it is rolling otherwise.
Clearly, holding on an incline would slip the clutch.
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What about stopping with the brake or hill hold assist would this disengage the clutch or should it go to neutral / park?
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I suspect the same is true for early Honda Jazzes with CVT. There is a "start-clutch" mechanism with is, I believe mechanical. There are numerous cases regarding wear, or build-up of muck, on the plates causing a judder on starting movement. It was so prevalent that Honda extended their warranty on this element. Later CVT transmissions fitted have reverted to a torque converter starting "clutch".
I nearly always put our Jazz CVT into N if stopping for more than a moment or two.
Our car has a very slight judder on take off, which flushing and replacing the correct Honda CVT fluid has failed to cure.
It's liveable with, though (so far) as otherwise I really like the CVT driving experience and associated fuel economy.
Last edited by: Roger. on Sun 12 Feb 17 at 13:03
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>> What about stopping with the brake or hill hold assist would this disengage the clutch
>> or should it go to neutral / park?
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That's the recommended way. Aplying the handbrake and leaving the selector at D leaves the clutch dragging, at least for a few seconds.
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>> I don't think that's true. The manual for our DSG Roomster cautions against
>> "holding the car on the accelerator".
This means revving the engine to stop it moving backwards when stopped on a slope.
The actual clutch wear is minimal in any creep scenario in a DSG - just because the clutch is slipping doesn't mean it's wearing at any significant rate.
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I'm glad FF said that, I'm not a tech but I must say, I was thinking that the design would take care of the (existing) driving habits of people, and that they wouldn't introduce something which had such an obvious "defect" without having "solutioned" it properly.
These companies spend millions on R&D...
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I dont disagree that allowing the car to move slowly along on tickover on a level road is unlikely to do.much harm.
OTOH the manual specifically says do not hold the car on the accelerator, something which some people will do, especially if they have not read the manual or thought about why it says that.
You're right in a way Smokie, the gearbox is programmed to deal with this, i.e. if
it gets too hot it shuts down. They still tell you not to do it.
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I don't believe the clutches in a DSG 'box do "wear" in the same way as a manual gearbox clutch. I have two DSG cars, one on 118k and one on 67k with 4wd and a frequently used towbar. There are no signs of anything wearing out on either car's drivetrain.
I recently read an article on a 2006 Golf GTI DSG with 308k miles on the clock; it has had two replacement DSG ECUs but never needed any other transmission work.
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Is that not like all the contra-indications when you get a drug from the chemist? They list just about every ailment known to man - so if you suffer something they can say "I told you so"... :-)
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DCT clutch wear - DP
