Manual gears: Double clutching vs 'single clutching'? - Page 2
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Thread: Manual gears: Double clutching vs 'single clutching'?

  1. #11
    Handbrake Released blackbird's Avatar
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    Most domestic FWD manual transaxles I've worked on in the last few decades haven't used pilot bearings (which is a small bearing that is pressed into the end of the crankshaft). The manufacturers have worked around this requirement by using larger front input shaft bearings to handle the increased side loading on the input shaft.


    Quote Originally Posted by ProDigit View Post
    I want to learn about how much damage it would do, even with rev matching, if I press the clutch 1 time, vs dual clutching.
    From what it appears people telling me, there's little wear doing this.
    But does this work the same way for old manual transmissions as it does for "dual clutch manual" transmissions?
    You technically "damage" your engine just by starting it as there's microscopic wear. Same thing with any shifting and clutch use. Sure, parts are technically wearing down, but if you're using it as designed and with proper maintenance most modern engines and transmissions should have no problem going 150-200k miles or more.

    I can't say for certain what long-term affect double-clutching will have if you did it on every shift, but I can say GM doesn't design and require it on their new fully synchronized manual transmissions. We can play a game of "what if" though.

    What if you double-clutch and it slightly prolonged synchronizer life so they might last 250k miles instead of 200k miles, but the increased wear on the clutch release components like the throw-out (release) bearing being used twice as much causes that bearing to wear down more, the clutch disc eventually doesn't fully release, and that causes way more severe, way faster internal trans damage? Or engaging and disengaging the clutch twice as much causes more wear on the crankshaft's internal thrust bearing, which counteracts the side loads placed on the crankshaft by the clutch mechanism. I doubt it would be a problem on the Cruze's engines but some other older engines from other automakers would have problems with "crank walk" where that bearing wears down and allows the crankshaft to start moving sideways.

    There's probably a lot of scenarios and I haven't torn into any of these transaxles to see what they look like at really high mileage and what their common failure mode and wear items will be. I'd still suggest shifting normally, be gentle and not slam gear changes, and if you do race the car on a track maybe use double-clutch for multi-gear downshifts.



    By the way, not sure what you mean by "dual clutch manual" transmissions. I'm not sure if you might be getting confused by how the word clutch is being used. When someone says "double-clutch" they're using the word clutch as a verb to describing and action of pushing the clutch pedal twice. In a dual-clutch automatic transmission the word clutch is a noun and describing the actual physical part, of which means two separate clutch discs/packs (i.e. the actual friction material assembly).

    There are dual-clutch automatics which have similarities to a manual trans but have two physically different clutches, with one clutch or clutch pack connected to half the gears in the trans and the other clutch connected to the other half. It's difficult to describe in text but you can search on the internet for some nice visual schematics.
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  3. #12
    ProDigit is offline [OP]
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    Lol, yes, dcts is what I meant.
    Not to get confused here, I'll refer to the part as DCT, and the action as dual clutching.
    The first time i heard about DCTs was on the cruze automatic.
    Now I hear there are DCT manual gears as well.
    I wonder how these DCTs respond to double clutching.

  4. #13
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    Quote Originally Posted by ProDigit View Post
    Lol, yes, dcts is what I meant.
    Not to get confused here, I'll refer to the part as DCT, and the action as dual clutching.
    The first time i heard about DCTs was on the cruze automatic.
    Now I hear there are DCT manual gears as well.
    I wonder how these DCTs respond to double clutching.
    Huh?

    The Cruze was never a dual-clutch automatic. It's a traditional planetary automatic gearbox with a torque converter.

    Cars like the VW GTI/Golf R, Ford Focus, Mercedes CLA/GLA, Acura TLX, BMW M3, and lots of other expensive sports cars have dual clutch automatic transmissions. Such a transmission is all computer controlled - it's an automatic transmission with a series of clutches to swap cogs rather than a torque converter and planetary gearsets. Most of these transmissions are very jerky in traffic and at low speed, but they shift extremely quickly and are excellent for performance applications.

    This has nothing to do with rev-matching or "double clutching" on a manual transmission.
    Last edited by jblackburn; 05-31-2018 at 03:30 PM.
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  6. #14
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    In driving manual transmission cars since... since I learned to drive in the '70s, I got the feeling that, when downshifting, revving the engine with the clutch disengaged, that is, without double clutching, also eased the selection of the lower gear, eased the work of the synchronizer. Not really sure it's true of this car, yet. I am a gentle, economy-focussed driver most of the time. And, the driving conditions around here don't require aggressive downshifts for the most part.

    A separate consideration: Revving the engine before releasing the clutch saves wear on the clutch and avoids shock to the mechanicals and body of the car.

    I had a 2001 Sentra that had a positively-regarded 5 speed manual transmission. When I changed out the gear oil for Amsoil Synchromesh, the shifting speed and ease was greatly improved. If you want to extend the life of your manual transmission, as well as your enjoyment of driving, I'd recommend this product. Other, more experienced people here also recommend this.
    Last edited by 17Hatch6MT; 06-01-2018 at 06:51 AM.

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