Double Clutching?

[Zeusimo]

So I Was With My Friend, She Was Driving Her Car And Using The Clutch Twice To Shift Once

 

As In Clutch Pedal In, Neutral, Clutch Pedal Out, Clutch Pedal In, Next Gear, Clutch Pedal Out

 

Is There A Point To This? :blink:

 

I Just Push Clutch Pedal In, Next Gear, Clutch Pedal Out...

[izzo]

dunno why she does that, maybe her dad was a truck driver lol

[Leprechaun311]

You do this when your syncros are weak, or getting a mild crunch and there is nothing else you can do (have tried all the exotic synth oils and such).

 

Also, good practice matching revs, as when your clutch cab;e goes BOING this is close to what you'll be doing on each shift to get home (without a flat bed).

 

I bought a roadster with a weak 2nd syncro, and have to double-clutch both 1-2 and 3-2. Now when I get in any other car I can't help myself.

[datzenmike]

It's the job of the synchro to speed match the spinning gear parts so they can engage without 'grinding'. Double clutching isn't really necessary on an up-shift as the lower gear is spinning faster than the next so all you have to do is shift slowly and it will naturally slow down and when close, engage. A very fast up-shift will force the synchro to slow the input shaft. Double clutching is more effective when down shifting. Letting out the clutch in neutral and revving the motor will spin the input shaft up closer to a match in speed and takes some of the effort off the synchro.

[I'm BLUE]

I do this most of the time (75% or when I can),,, works well with WORN transmissions ,,, I believe it pro-longs life of good condition ones ,,, it can't hurt but wear the clutch a bit ,,, ollz

 

I have a ranger with a light bark feel (light light grind in 3rd) ,,, if I don't double clutch it ,,, I feel it ,,, If I do double clutch it ,,, almost never feel it ! I always double clutch in 3rd on my truck ,,, or at least when possible ,,,

 

I also REV Match on mostly down-shifts and try to on upshifts if not in hasty traffic ,,, much smoother ,,,

 

I learned this from a truck driver haha ! drove a dump-truck with no synchro's ,,, I got to try it ,,, interesting experience !!! ,,, I have been sold since !

[littlejason]

Yeah. I do it on downshifts, really just to preserve synchros, not because I'm racing or whatever. However, it drives me insane when I ask my wife a million times "please come to a complete stop before shifting to 1st." The choice is yours.

 

Edit: Oops, too slow. Sounds like you already know exactly what I'm saying.

[Jayden71]

When I taught CDL school I had to teach doublee clutching. Big truck transmissions,(9, 10 13 15 and 18spd) do not have synchros in them. Synchros cannot go a million miles or handle the demands of heavy driving. However once you learn to double clutch you quickly learn to speed shift and only use the clutch for starting and stopping.The 13spd i currently drive can handle up to 550hp and 1850 ft lbs of torque

[RadioRedline]

http://www.youtube.com/watch?v=W7bt1E30y0A

 

GRANNY SHIFTING NOT DOUBLE CLUTCHING LIKE YOU SHOULD!

 

Radio

[HRH]

Vin Diesel sucks. I'd save double clutching for trucks or straight cut gear boxes (dog box, racing transmissions). Other than that, it's a waste of time save prolonging the transmission on vehicles that have less than new synchros. I should probably do it with the hardbody, but I just don't care that much. Eventually I'll rebuild the transmission just like I've rebuilt the rest of the truck. (Slightly grunchy shift usually 1st to 2nd from time to time.)

 

However, I can easily rev match and shift the truck without using the clutch. However, my Datsun guru and I had a discussion on whether this practice actually hurts the synchros on gearboxes equipped with them. I'm not entirely certain.

 

And Zeusismo, why the fuck haven't you gotten rid of your shift key yet?! Break the habit! If I was at your house right now I'd be rapping your knuckles with a ruler!

[Yosemite_Sam]

http://www.youtube.com/watch?v=W7bt1E30y0A

 

GRANNY SHIFTING NOT DOUBLE CLUTCHING LIKE YOU SHOULD!

 

Radio

 

 

I was about to go and find this, but you beat me to it.

[RadioRedline]

You almost Had me?! You never had me...You never had your car...

 

Lol

 

Radio

[justin 620]

"Whether you win by an inch, or a mile. Winning's winning."

[Guest 510kamikazifreak]

Oh god,now they are talking like fast and flurry...

abort this...crap...

[flatcat19]

Oh god,now they are talking like fast and flurry...

abort this...crap...

 

Yessir!

[metalmonkey47]

My syncro in 2nd is gone, so during a down shift into 2nd, I usually rev match (double clutch) Works great with no grind!

[wayno]

I haven't double clutched in over 30 years, after you blow a few clutch discs doing compression skids, you learn not to do that. Depends on the tranny when it comes to shifting without the clutch, a very few can take it, like the borg warner T10, shifted without a clutch for a year, the clutch pedal assembly kept breaking, due to the 3500lb pressure plate(3 finger clutch cover), got tired of it and went back to the stock type, beleave it or not, the starter lasted the whole time I owned the car, a 1965 Nova SS with a built 350, 13 sec. 1/4 miles. Yahoooooo

[Stupid_fast]

Meh double clutch only when you have to , my ZX trans grinds into 5th so I double clutch up! Also any lower gears downshifting I always double clutch down, 2nd will make some nice chatter/whinning if I don't double clutch down from 3rd, same with 1st. (if I need 1st ... slow speed ~10mph corner? faster pull-away)

 

Same with even a great condition S2000 or 350z trans, blocks you from going into 1st if going over 15mph(input shaft turning too quick ... synchro acts as clutch), hard to get into while traveling ~10mph ... So if needed clutch in and give it some revvs, goes right in. Helps smoothness of driving and probably saves some wear.

 

The reasoning for the lower gears is that I live in the hills, all the roads around here are steep. There are some really hard hills that I roll up instead of stopping on. Too hard to get going, or e-brake wont hold the car ! Sometimes 1st is required. Won't accelerate in 2nd at 10mph up some of these hills here.

 

 

And lol @ the fast & furrius, almost blew those intake welds! I wonder if they are JB-welds?

 

 

Nevermind JB-weld is too strong... JB quik?

[albyneau]

There's a shred of truth in nearly every post here~ save the straight cut gears.

First, the gear tooth angle has nothing to do with syncronizer function, and everything to do with load bearing capabilities, power transmission, and noise. An examination of any syncro design will prove testament. Straight cut gears "push" eachother into rotation, decreasing contact area, and increasing the load to contact patch area- hence the noise. Second, the cross-sectional strength of a straight-cut gear is reduced compared to beveled gears. Beveled gears "swipe" eachother into rotation, reducing noise, load, and wear (due to shear strength of fluids). Additionally, the gear teeth are "wider" when measured (or loaded) at a bias, or diagonal~ so the effective load is pushed through thicker metal. Gear lubes ( and most all lubricants for that matter) do relatively poorly under perpendicular loads (film strength) as opposed to shear loads. Shear loads (as in bevel or helical cut gears) not only push oil out on the alee side, but pull it IN to the contact patch on the aweather side. Straight cut gears make a helluva noise, but transfer loads with less power loss due to shear. One's for power, the other longevity.... 'Nuff said bout gears...

 

Double clutching has only one benefit~ to aid in the matching of input/output RPM's when shifting. There are only two scenarios where this benefit proves itself worthy: one is when the design/condition of the synchros is insuffficient to control the rotating mass of the powertrain involved, and the other when said rotating mass (as in bigrig) is so large additional technique to smoothly transition gear changes. See *inertia* http://en.wikipedia.org/wiki/Inertia

 

As a P.S. in regards to above scenarios~ liberal and attentive operation of the throttle becomes as much of the equation as clutching techniques~ so should we as well refer to it as "double-gassing"... ? :lol:

 

Peace~

Scott

[dirtydiesel]

Yeah. I do it on downshifts, really just to preserve synchros, not because I'm racing or whatever. However, it drives me insane when I ask my wife a million times "please come to a complete stop before shifting to 1st." The choice is yours.

 

Edit: Oops, too slow. Sounds like you already know exactly what I'm saying.

 

 

the only time i use first gear is in my friends honda cuz she dont have second. and when my diesel truck is loaded and on a tall incline. fuck first gear...i just dont touch it

[HRH]

I mention the straight cut gears because a lot of racing dog boxes don't have synchros.

 

And even though I hate F&F, I actually have seen the welds on a manifold blow. In fact, it was a homemade intake, but wasn't round, it was flat. It actually ripped the flap around the welds just like a box top. Engine braking created back pressure on the weak portion of the intake and pushed it up for the rip, and then it just sucked back down on throttle. Needless to say, that guy trailered it home.

[bananahamuck]

There's a shred of truth in nearly every post here~ save the straight cut gears.

First, the gear tooth angle has nothing to do with syncronizer function, and everything to do with load bearing capabilities, power transmission, and noise. An examination of any syncro design will prove testament. Straight cut gears "push" eachother into rotation, decreasing contact area, and increasing the load to contact patch area- hence the noise. Second, the cross-sectional strength of a straight-cut gear is reduced compared to beveled gears. Beveled gears "swipe" eachother into rotation, reducing noise, load, and wear (due to shear strength of fluids). Additionally, the gear teeth are "wider" when measured (or loaded) at a bias, or diagonal~ so the effective load is pushed through thicker metal. Gear lubes ( and most all lubricants for that matter) do relatively poorly under perpendicular loads (film strength) as opposed to shear loads. Shear loads (as in bevel or helical cut gears) not only push oil out on the alee side, but pull it IN to the contact patch on the aweather side. Straight cut gears make a helluva noise, but transfer loads with less power loss due to shear. One's for power, the other longevity.... 'Nuff said bout gears...

 

Double clutching has only one benefit~ to aid in the matching of input/output RPM's when shifting. There are only two scenarios where this benefit proves itself worthy: one is when the design/condition of the synchros is insuffficient to control the rotating mass of the powertrain involved, and the other when said rotating mass (as in bigrig) is so large additional technique to smoothly transition gear changes. See *inertia* http://en.wikipedia.org/wiki/Inertia

 

As a P.S. in regards to above scenarios~ liberal and attentive operation of the throttle becomes as much of the equation as clutching techniques~ so should we as well refer to it as "double-gassing"... ? :lol:

 

Peace~

Scott

 

 

 

 

...........He said

..perpendicular..

[moparvwfreak]

i really should do this in my Passat. 2nd gear grinds almost all the time when i shift into it. but only 2nd gear. alot of people complain about that in the 02x series transmissions. hell even the one in my jetta grinds 2nd. but right now i have bigger issues to solve, like a blown oil cooler..... AGAIN!

[BURLEIGH]

Yeah, I just "double gas" it when down shifting...

 

Clutch in, foot on brake, heel blibs throttle, shift down, clutch out... I only do this to get the engine speed to match the gearing though to keep the vehicle from "lurching" around a hard corner when I get back on the throttle...

[ripetomatoes]

Yeah, I just "double gas" it when down shifting...

 

Clutch in, foot on brake, heel blibs throttle, shift down, clutch out... I only do this to get the engine speed to match the gearing though to keep the vehicle from "lurching" around a hard corner when I get back on the throttle...

 

heel-toe technique ftw!