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Double Clutch Shifting [Merged 11-8] clutching synchronizing

Posted by Jello_Rolls, Oct 23, 2002

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  1. Defiant

    Defiant DSM Wiseman

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    Well, just have a seat here, m'dear, let me show you how all these complicated things work, hehehehe..... oh, there's a barfbag there in the glovebox, if you need it.....:D
     

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    1995 Eagle Talon TSi AWD
    manual · 2G DSM
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  2. Kicka$$93laser

    Kicka$$93laser Proven Member

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    Hey thanks for all your help everyone, specially you Defiant, although i dont think ill be needin
    a barf bag, im pretty use to gettin thrown around in fast cars!! I LOVE IT!!
     
  3. lenz

    lenz Proven Member

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    i have heard people talking about double clutching when there racing but how do you do it and does it really help.
     

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    1992 Mitsubishi Eclipse N/T
    · 1G DSM
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  4. Defiant

    Defiant DSM Wiseman

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    Pay attention, I'm only doing this a thousand more times:

    1. It's ONLY for downshifting.

    2. If done correctly, with a modicum of coordination, it IS good for the synchros.

    3. It will take you a month of practice to get good at it. Once you do, you will never think about it, nor ever drive a stick again without doing it.

    4th gear. 50 mph. Coasting down. Press in clutch, shift to N. Let out clutch. Blip throttle, ignore the tach, just give it a blip. Press in clutch. Shift to 3rd. Let out clutch.

    That is double-clutching. You're bringing the gearbox guts up to speed with the rear end, the engine speed, and the speed all will be going in the next-lower gear. Your synchros will stir less than the cat at the foot of the bed in a sound snooze. And like the cat, they will greatly enjoy the rest.
    As you get practiced at it, work on learning 5th to 4th -not too tough- then the important one, 3rd to 2nd. THIS is the one that matters most- the 2nd gear synchro is blown on virtually all DSMs, from ham-handed gorillas blanging the poor bastards down into second like a Vandal ramming his dick into a conquered king's virgin. Like Chevy drivers with rockcrusher gearboxes, if you will.
    When you do it right -and you will KNOW- it's amazing. The downshift slides in as though the cables have come adrift of the shifter arm.
    You want to get the shift down finished before the engine and gearbox have slowed down from the blip, but don't try to think about it, it'll screw you up worse than trying to "fix" a golf swing. Be the machine, pissant, and the machine will do your bidding.
    Then you'll be able to ask about heel-and-toe, double-declutch downshifting at speed.
     

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    1995 Eagle Talon TSi AWD
    manual · 2G DSM
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  5. Defiant

    Defiant DSM Wiseman

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    I've still not seen F&F, and I don't know what they're calling double-clutching in the movie. But from what I've seen float up on the boards, it has less to do with reality than Pandora Peak's jugs.

    One other thing: NEVER downshift to first on the road. Autocrossing, yes. Road, no. Second will move the car from a stop, you'll just have to live with losing first place. And your engine will live, too.
     

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    1995 Eagle Talon TSi AWD
    manual · 2G DSM
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  6. dsmrunnah95

    dsmrunnah95 Proven Member

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    The other form of double clutching uses the same principle as the one that Defiant stated except it's going up through the gears instead of downshifting. Let's say you have it in first, put it in neutral, tap the throttle, put it in second. These methods were used for older cars that didn't have enough power to pull the low part of the gear.
     
  7. Defiant

    Defiant DSM Wiseman

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    ? ? ? err... you have to double-clutch upshift if the transmission is a pure crashbox, with no synchromesh. It's not a matter of power -early engine designs were known for high torque at low speed- it's getting the gears to mesh without grinding. You'd never tap the throttle on upshifting, as that cancels the effect you're trying for, which is to get the layshaft gear cluster to _slow down_ enough to let the next-higher gear engage.
     

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    1995 Eagle Talon TSi AWD
    manual · 2G DSM
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  8. darkrage

    darkrage Proven Member

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    I had a friend who thought "double clutching" was tapping the throttle with the clutch pedal up inbetween switching gears.... his tranny was gone about 3 weeks later


    do what I just told you but dont hit the throttle, and that is real double clutching, it helps save your synchros
     
  9. Mr Mike

    Mr Mike Proven Member

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    If your syncros are already bad, double clutching can keep the gears from grinding. My fifth gear syncro is bad so when I shift up to fifth I just put it in neutral first, let the transmission whine down for a second or two, and then put it into fifth. Otherwise it grinds going into fifth everytime.
     
  10. Defiant

    Defiant DSM Wiseman

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    I've heard that called "double-kicking", but I don't know if that was just a local term my dad had picked up in the 40's. You use (well, I use) the same method on a motorcycle when I downshift- I don't use the clutch to downshift (I clutch upshifts) on the bike until actually stopping, but goosing the throttle just as you're coming off the higher gear and just before you get the next lower (sequential gearboxes, no real neutrals between gears on bikes, and no synchros on dog clutch gearboxes) engaged, you give it a slight blip so that when you hit the lower gear it doesn't break the rear tire loose.
    In a car, if you put in the clutch and downshift, blipping the throttle before you let the clutch back out will also keep the traction tires from breaking loose, and is less wear on the clutch friction disk when you let the clutch back out. But it's still making the synchros work as you're sliding into the lower gear and the synchros are having to brake (not slow down, but speed up) the cluster gear in order to let the selector collar engage.
     

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    1995 Eagle Talon TSi AWD
    manual · 2G DSM
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  11. TalonESi

    TalonESi Proven Member

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    I've always wanted to know what the difference is between this and just pressing the clutch in and giving it a blip before switching gears, instead of putting the transmission into neutral.
     

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    1995 Eagle Talon N/T
    manual · 2G DSM
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  12. Defiant

    Defiant DSM Wiseman

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    You're not bringing the transmission up to speed in doing this: it'll rev-match the motor, which saves the friction disk wear, and keeps the traction tires from losing traction, but the synchros are still having to bear the force of bringing the cluster gear up to speed with the driveline, which is still connected to the road. By going into neutral, letting out the clutch and then blipping it, you're speeding up the gears to the speed of the driveline and taking the strain away from the synchros.
    The car was doing fifty, the transmission gear train in 4th was doing fifty, but the transmission gear train was _not_ doing 50 in third; double-clutching "fakes" the third-gear geartrain up to 50, instead of making the synchronizers do it by friction.
     

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    1995 Eagle Talon TSi AWD
    manual · 2G DSM
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  13. TalonESi

    TalonESi Proven Member

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    Cool, nice explaination Defiant, I understand.
     

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    1995 Eagle Talon N/T
    manual · 2G DSM
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  14. rookieupgrade1

    rookieupgrade1 Proven Member

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    Well said. Best description I have seen so far.

    :laser:
     

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    1993 Plymouth Laser N/T
    · 1G DSM
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  15. Bad93ex

    Bad93ex Proven Member

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    how do you double cltuch anyways?
     
  16. got_no_sol

    got_no_sol Proven Member

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    let's say you're going 40 in 3rd.....

    depress the clutch, take to neutral, let off clutch, rev to whatever your rpm in 2n'd will be,
    press the clutch in - shift to 2nd, let go of clutch...

    With some practice you can do this in one fluid quick motion - just takes some practive... :thumb:
     
  17. Bad93ex

    Bad93ex Proven Member

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    I usually just try avoiding 2nd now because of the grind.
     
  18. Defiant

    Defiant DSM Wiseman

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  19. Defiant

    Defiant DSM Wiseman

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    Double-clutching will help your synchronizer rings last 250K miles. At least, it has the ones in my Datsun roadster, which also "doesn't need it".

    130K in the '93, 80K in the '95, so far.

    Once you learn it, you'll never go back.
     

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    1995 Eagle Talon TSi AWD
    manual · 2G DSM
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  20. Grimis

    Grimis Proven Member

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    my father also used this in his rig, driving truck for 34years, can use it both ways. Cuz if you think about it, about the movie, Why would he be worried about Double Clutching when Down shifting :confused: :confused:
     
  21. got_no_sol

    got_no_sol Proven Member

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    That was a truck, These are newer cars. There is no need to double clutch up shift in a dsm.
     
  22. temfate

    temfate Proven Member

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    Double Clutching is just a little easier for a tranny. It prevents some damage as Defiant has pointed out, and when your tranny already grinds in sometimes will help it not to.

    As far as the spupidity of pressing in the clutch only to let it out for a speed boost. What you are feeling in the speed you LOST while pushing down on the clutch. Slipping it will desingage the true speed of the engine from the wheels, thus when you release it this speed difference manifests itself as a jump. This will do nothing more than slow you down in a race, kill your clutch, and kill you drivechain in general...
     
  23. kpt4321

    kpt4321 Proven Member

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    You don't need to double clutch to upshift in any vehicle, and I urge anyone who thinks otherwise to prove to me why.
     
  24. Aikouka

    Aikouka Proven Member

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    It can also be used in RWD (not AWD) vehicles to start drifting.

    All the times I've read this thread, I've always wanted to make some F&F comment/blurb about "granny shifting" :p.
     
  25. VOTBLINDUB

    VOTBLINDUB Proven Member

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    instructions are here
     

    Attached Files:

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    1998 Mitsubishi Eclipse N/T
    automatic · 2G DSM
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