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Do you shift w/o using your car's clutch?
Posted by: Jp!
Date: July 17, 2007 06:00AM
I haven't owned a manual shift transmission vehicle for some time now. But when I did (and I had a few) I would often shift without using the clutch. Timed just right, the cars/trucks I owned had no problem with it at all.

I had forgotten all about that until just now, when I saw this article/video. (Well, I did not watch the video).

[www.autoblog.com]

I never downshifted clutchlessly, just upshifts. And I can't recall if I ever tried or did that with any of my motorcycles, either. I don't think so.
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Re: Do you shift w/o using your car's clutch?
Posted by: Tofer
Date: July 17, 2007 06:40AM
I've done it a few times, but only for my own edification. It feels a little strange, but as you say, if you time it right, it is kind of cool.

-Tofer
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Re: Do you shift w/o using your car's clutch?
Posted by: Mr645
Date: July 17, 2007 07:10AM
I probably use the clutch about 75% of the time
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Re: Do you shift w/o using your car's clutch?
Posted by: billb
Date: July 17, 2007 07:44AM
Friend let me drive his Kenworth on 87 North in New York hauling Frito-Lay to Montreal, when we were very young, for a couple hours. He insisted I get the hang of it.

A light car is a piece of cake.
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Re: Do you shift w/o using your car's clutch?
Posted by: Jp!
Date: July 17, 2007 07:51AM
Yikes. I find that hard to believe. Frito-Lay Logistics is very strict on their policies. He could have lost his job for that THAT DAY.
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Re: Do you shift w/o using your car's clutch?
Posted by: h'
Date: July 17, 2007 07:52AM
I'd say pretty near 100% of my shifting is clutchless.
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Re: Do you shift w/o using your car's clutch?
Posted by: cbelt3
Date: July 17, 2007 08:20AM
only to take it out of gear. Otherwise the clutch foot comes down automatically.

Which annoys my wife when I drive her automatic minivan, because my left foot keeps thumping to the floor when the tach reaches 3K.
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Re: Do you shift w/o using your car's clutch?
Posted by: billb
Date: July 17, 2007 08:26AM
Quote
Jp!
Yikes. I find that hard to believe. Frito-Lay Logistics is very strict on their policies. He could have lost his job for that THAT DAY.


1973

I couldn't be in the truck on either end.
(technically not between, either)
Which meant I got bumped on a corner in Montreal. It doesn't take long to empty a trailer of corn chips.
Bumped out for the load return, too. Pepsi, if I recall. Not liquid, not heavy. Never saw either loading dock in Montreal.
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Re: Do you shift w/o using your car's clutch?
Posted by: olnacl
Date: July 17, 2007 08:29AM
Had many occassions to drive w/o the clutch when linkage, slave cylinders failed. The trick is starrting from a dead stop. (you put the car in 1st and crank the engine - it's a little bumpy for the first couple seconds and it takes a toll on starter motors if done frequently - do not try it on an uphill grade :-))



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Re: Do you shift w/o using your car's clutch?
Posted by: Jp!
Date: July 17, 2007 08:30AM
oh, that explains it. I rode along in 88 and they had already installed GPS and TONS of tracking. Easily could get dinged every day for going to fast, too slow, stopping in the wrong places..
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Re: Do you shift w/o using your car's clutch?
Posted by: Lux Interior
Date: July 17, 2007 09:13AM
Chuck Norris shifts his transmission using sheer intimidation.
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Re: Do you shift w/o using your car's clutch?
Posted by: Carnos Jax
Date: July 17, 2007 10:52AM
Speaking based on a 'theoretical' understanding of manual transmissions, I realize you can supposedly do a clutchless shift. But even if executed perfectly (meaning you time the gear engagement so as not to cause any grinding, etc.), a clutchless shift imposes huge torsional loads in the drive line.

I figure that this would cause a dramatic reduction in the life of your driveline components because of such things as fatigue failure (i.e., things breaking because of repeated loads) happen sooner when the loads are higher.

I say a dramatic reduction in the lifetime of the part because the relationship between fatigue failure and the magnitude of the load isn't linear, it's exponential (meaning that doubling the load for example will more than halve the lifetime of the part).

Do you guys who power shift all the time notice a higher than normal rate driveline failures (not necessarily restricted to the transmission)?
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Re: Do you shift w/o using your car's clutch?
Posted by: Don Kiyoti
Date: July 17, 2007 11:54AM
I seem to remember having the clutch cable break on my 1967 VW about 30 miles from home so that meant shifting with no clutch. It also meant starting the car in gear (VWs had pretty powerful starter motors), running the stop signs I could get away with, and stalling the car at the ones I couldn't.





[picasaweb.google.com] [www.flickr.com]
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Re: Do you shift w/o using your car's clutch?
Posted by: billb
Date: July 17, 2007 01:50PM
A clutchless shift puts no "extra" load on the drivetrain.
The input shaft and the "output shaft" (which is also your drivetrain) are spinning at the exact same RPM. There is NO load until engine RPMs are increased. If done correctly, it's actually quite a smooth effort.
Unless pointed downhill, taking off in first without a clutch for transfer is dumb. Once you have <some> momentum it's actually rather easy not to use the clutch.




Granny shifting: you hear the engine bog between shifts. (that clutch is getting warm )
Speed shifting : nice smooth transitions, ratherstable engine rpms between gears
Powershifting: High RPMs betweengears. (everything is getting warm)

clutchless shifting has no purpose except it can be done ,if you can listen to your drive train components and know when they are in sync. ( MIssing and grinding is Not good).



I've never tried it with an old transmission that had to be double clutched between gears.



Edited 1 time(s). Last edit at 07/17/2007 01:55PM by billb.
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Re: Do you shift w/o using your car's clutch?
Posted by: The Batman
Date: July 17, 2007 02:03PM
Having personally destroyed and repaired many manual transmissions in my life I can tell you that shifting without the clutch will wear out your transmission synchronizers quite fast. They are not cheap to fix either as they are deep-DEEP inside the tranny.

Without gettting too technical, the 'synchros' are like little friction clutches inside the transmission and each forward gear has at least one. They are designed to synchronize the input shaft speed with the outpout shaft speed (road speed) so that the gears do not grind when you shift. The main clutch (operated by the floor pedal) is designed to seperate the engine's rotational mass from the transmission driveline and make life easy on the synchros.

Sometimes it is necessary to shift without the clutch (like when it is broken) and clutchless shifting a few times carefully will not really kill your transmission, but I would not make a habit of it unless you have stock in AAMCO or something.....

Clutchless shifting really only hurts the synchros and nothing else in the driveline, but it is very, very hard on them as they are not designed for this heavy of a load on such a frequent basis.

Many times reverse does not have a synchro, thus if the car is moving even a tiny bit the gear will grind when shifting. As the synchros wear out on the other gears they lose the ability to sync the shaft speeds and eventually all gears end up like reverse and grind when shifting. Eventually the teeth will grind/chip off and cause all kinds of fun as metal particles float around inside the tranny.

Shifting without the clutch is cool of course, but should only be done to impress dates and such, not as a normal driving procedure.
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Re: Do you shift w/o using your car's clutch?
Posted by: Carnos Jax
Date: July 17, 2007 03:14PM
Quote
billb
A clutchless shift puts no "extra" load on the drivetrain.
The input shaft and the "output shaft" (which is also your drivetrain) are spinning at the exact same RPM. There is NO load until engine RPMs are increased. If done correctly, it's actually quite a smooth effort.

Guess I don't understand these things in a practical sense, but isn't the "input shaft" you're referring to come from the engine via the engine flywheel and clutch? I thought the clutch only disengages the engine flywheel (and hence the engine) from the input end of the transmission?
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Re: Do you shift w/o using your car's clutch?
Posted by: billb
Date: July 17, 2007 04:57PM
You got it.
Now just imagine that the input shaft is rotating at the same speed as the output shaft.

This happens in two scenarios.
1. Parked -- shaft speeds are both zero. (therefore identical, or, matching)
2. In motion -- when both shaft speeds are identical.

Shaft speeds is a bit simplistic. Technically it's the gears that have to be spinning at the same speed. Forget trying to calculate the gear reductions.



---------------------------------------------------------------------------
You're driving down the street at 25mph at 2000RPM.
It's time to shift.
You let your foot off the gas. The engine RPMs begin to drop and at some point (we'll say 1950 RPM) there is no pressure on the gears because they are spinning at the same speeds. It pops right out of 2nd gear easy into neutral.
Now you want third gera (which is a taller gear ratio). They'll "match" at an even lower engine RPM (say 950) at 950 RPM and just the right forward speed and incline (for sake of argument we're gonna assume you're good at this and you're still doing 25MPH (minus an almost insignificant amount) :-) ) they'll mesh again and it will pop right into third gear. repeat.
If you take too long and your engine RPMs drop below 950 it either won't go or will grind, you'll have to raise your engine RPMs to where the shafts that hold the gears are spinning at the same speed again.

Some trans this un-matched shaft speeds will feel rubbery in the shifter and become suddenly "light" when they match.

I bet I get better mileage with an auto. trans.
With an auto I just drive.
With a manual transmission I tend to have a bit of "fun" which costs.

It's just a balancing act of speeds not unlike a scale and weights.
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Re: Do you shift w/o using your car's clutch?
Posted by: vision63
Date: July 17, 2007 06:00PM
I say if you're too lazy to press down on the clutch, you need an automatic transmission. Ya Bum Ya's! No you can't drive my car!
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Re: Do you shift w/o using your car's clutch?
Posted by: Grateful11
Date: July 17, 2007 06:01PM
Quote
Don Kiyoti
I seem to remember having the clutch cable break on my 1967 VW about 30 miles from home so that meant shifting with no clutch. It also meant starting the car in gear (VWs had pretty powerful starter motors), running the stop signs I could get away with, and stalling the car at the ones I couldn't.

I remember the exact same thing happening to me on my '66 Beetle. I was like 12 miles
from home. Cable was like $10, at least it was easy to replace.



Grateful11
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Re: Do you shift w/o using your car's clutch?
Posted by: davester
Date: July 17, 2007 07:49PM
Ditto! The cable on my '68 Beetle snapped when I was in the middle of San Francisco. It was nightmarish trying to drive clutchless through the hilly city. I stopped at an auto parts store, bought a cable, and changed it during my lunch break at the docks (I was working with longshoremen unloading ships (before the container boom).



"In science it often happens that scientists say, 'You know that's a really good argument; my position is mistaken,' and then they would actually change their minds and you never hear that old view from them again. They really do it. It doesn't happen as often as it should, because scientists are human and change is sometimes painful. But it happens every day. I cannot recall the last time something like that happened in politics or religion." (1987) -- Carl Sagan



Edited 1 time(s). Last edit at 07/17/2007 07:50PM by davester.
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Re: Do you shift w/o using your car's clutch?
Posted by: vision63
Date: July 17, 2007 10:46PM
Quote
davester
Ditto! The cable on my '68 Beetle snapped when I was in the middle of San Francisco. It was nightmarish trying to drive clutchless through the hilly city. I stopped at an auto parts store, bought a cable, and changed it during my lunch break at the docks (I was working with longshoremen unloading ships (before the container boom).

That was an interesting job!
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Re: Do you shift w/o using your car's clutch?
Posted by: Mike V
Date: July 18, 2007 08:48AM
Yeah, doesn't this totally destroy the Synchromesh?

You can only do this without damage on a dog box can't you?



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