Clutchless Shifting/ Shifting Techniques

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Max Slowik
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Clutchless Shifting/ Shifting Techniques

Post by Max Slowik » Sat May 19, 2007 10:03 am

jaganath
waaay off-topic,but how does one change gear w/o a clutch?
To answer:

JimX
Move shift to neutral, rev up and, as revs start decreasing, gently push stick in next gear. It will get in at some point.
and

JazzJackRabbit
offtopic, theoretically if you perfectly match RPMs there shouldn't be any harm.
Yep.
We used to train doing this when I was young. And in some cars (usually Japanese), it's really fast.
And a great skill to have. It's also useful if, like I, drive a little too rally-inspired. Also, you probably need to know this if you're driving a diesel truck. Like the kind that hauls concrete, not just a big pickup. It might come in handy when you're moving and that's the last truck on the lot, because it's part of double-clutching.

Ah Hell, lemme Google. . .

http://www.waycoolinc.com/z3/essentials ... ifting.htm

Lt_Dan
that dosen't sound very good for the transmission.
Surprisingly, it's OK for the transmission; it actually decreases wear because it doesn't use the clutch (obviously) and the synchro-mesh hardly has to do any work.

Assuming you don't grind your junk to bits screwing it up :)
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Post by JimX » Sat May 19, 2007 10:17 am

Assuming you don't grind your junk to bits screwing it up :)
:lol:


I did destroy some 2nd gear synchromesh, in more than 1 car, but it wasn't by using no clutch. It was either by downshifting in high revs, then releasing clutch to start a drift (in RWD), or by shifting too fast from 1st to 2nd. Sometimes it didn't work. :lol:

Max Slowik
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Post by Max Slowik » Sat May 19, 2007 11:30 am

Second gear is always the first to go. It's a great tell if a car has had easy or hard miles if the second gear shifts funny.
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continuum
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Post by continuum » Mon May 21, 2007 9:46 pm

It only does no additional wear if you shift perfectly. That's extremely difficult to do.

Clutchless upshifting is theoretically easy, but in reality I find blipping the throttle on a downshift to make for an easier rev-match.

However, 99.999% of people who try to shift a conventional helical-geared synchromesh gearbox (e.g. every production car made today) without the clutch are NOT going to do it right, and they are going to bang the gears around and increase the wear. I personally recommend they replace a $150 clutch disc (or $250-450 if they wear out the whole assembly too) rather than a $800+ transmission rebuild. :p

On a transmission with straight-cut (dog-cut) gears, clutchless shifting is easier and considerably less damaging, but it still has to be done properly.

I don't know about 2nd gear always being first to go, in many newer transmissions, 3rd gear is actually the weak like. The Aisin-built 6-speed boxes in both the Mitsubishi Evo8/Evo9 MR-trim tends to fragment 3rd gear as low as 300whp, and in the B13 (91-94) Sentra SE-Rs, 5th gear's syncho and shift fork tend to wear out first, resulting in 5th-gear-pop-out.

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Re: Clutchless Shifting/ Shifting Techniques

Post by aristide1 » Tue May 22, 2007 10:02 am

Max Slowik wrote:jaganath
waaay off-topic,but how does one change gear w/o a clutch?
I used to do this with a 1972 Chevy Vega, and a 1968 Chevy Impala 6 cylinder with 3 speeds on the column (Dad's taxi).

I found I was not capable of doing this under various conditions, but only with moderate acceleration.

In first gear with part throttle the engine would gradually reach a moderate speed and not supply any more power. I would push my hand up on the column shift. When a sort of equilibrium was reached, engine and car speed, the shifter simply fell out of gear. At that point I took my foot off the gas. As the the engine slow it then would reach an rpm that was pretty close to second gear and I could ease it into gear. I sort of found out about the whole thing by accident, I never really developed much interest in it.

Dad's taxi was as stripped as stripped could be. 1 barrel 250CID 6 cylinder. 3 on the tree, no power steering, no power brakes, all drum brakes, and only an AM radio. And first gear had no synchronizer, can you spell G-R-I-N-D? You had to come to a complete stop in order to get into first gear without the whole neighborhood hearing about it.

The Vega was similiar, but the rate of acceleration using this method was usually too slow. I never cared for the trans that was offered in the first 2 years, 1971 and 1972, I think it was an Opel import. By 73 they switched to a solid Saginaw 4 speed.
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Post by aristide1 » Tue May 22, 2007 10:07 am

JimX wrote:
Assuming you don't grind your junk to bits screwing it up :)
:lol:


I did destroy some 2nd gear synchromesh, in more than 1 car, but it wasn't by using no clutch. It was either by downshifting in high revs, then releasing clutch to start a drift (in RWD), or by shifting too fast from 1st to 2nd. Sometimes it didn't work. :lol:
In the days of all drum brakes and long hills brake fade was an issue. You either downshifted like a truck or you didn't stop, take your pick. And power drum brakes make no difference at all.
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Re: Clutchless Shifting/ Shifting Techniques

Post by disphenoidal » Tue May 22, 2007 8:43 pm

aristide1 wrote:
Dad's taxi was as stripped as stripped could be. 1 barrel 250CID 6 cylinder. 3 on the tree, no power steering, no power brakes, all drum brakes, and only an AM radio. And first gear had no synchronizer, can you spell G-R-I-N-D? You had to come to a complete stop in order to get into first gear without the whole neighborhood hearing about it.
'68 Impala was a cool looking car. But I can only imagine how long it would take a 250-cube 6 to get that much metal moving. Or how hard it would be to get it stopped with drum brakes at all four corners.

Actually, I have some idea. My enormous Fleetwood Brougham has a 250-cube V8 that probably makes about 120hp. So I wouldn't call it fast, either.
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Post by EndoSteel » Wed May 23, 2007 12:57 am

continuum

However, 99.999% of people who try to shift a conventional helical-geared synchromesh gearbox (e.g. every production car made today) without the clutch are NOT going to do it right, and they are going to bang the gears around and increase the wear.
Usually it takes much less time to learn proper clutchless shifting than to actually kill the gearbox :).

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Re: Clutchless Shifting/ Shifting Techniques

Post by aristide1 » Wed May 23, 2007 8:00 am

disphenoidal wrote:
aristide1 wrote:
Dad's taxi was as stripped as stripped could be. 1 barrel 250CID 6 cylinder. 3 on the tree, no power steering, no power brakes, all drum brakes, and only an AM radio. And first gear had no synchronizer, can you spell G-R-I-N-D? You had to come to a complete stop in order to get into first gear without the whole neighborhood hearing about it.
'68 Impala was a cool looking car. But I can only imagine how long it would take a 250-cube 6 to get that much metal moving. Or how hard it would be to get it stopped with drum brakes at all four corners.

Actually, I have some idea. My enormous Fleetwood Brougham has a 250-cube V8 that probably makes about 120hp. So I wouldn't call it fast, either.
If I would stay at 55 mph the Impala got 20 mpg on the highway. Around town it was less.

I tried one day and discovered it's top speed was only 75mph, 3/4 or full throttle, made no difference.

Like engines of that time around 80,000 miles the timing chain was worn out as were the distributor bushings. Replace those 2 items and the thing ran like new. Mileage and power would increase substantially. Since you had to remove the water pump you may as well replace that too, it wasn't going to last much longer anyways.
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Post by aristide1 » Wed May 23, 2007 8:06 am

EndoSteel wrote:continuum

However, 99.999% of people who try to shift a conventional helical-geared synchromesh gearbox (e.g. every production car made today) without the clutch are NOT going to do it right, and they are going to bang the gears around and increase the wear.
And I expect the 99.999% estimate to be low. 8)
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Post by Agent_N » Sat May 26, 2007 6:10 pm

continuum wrote:It only does no additional wear if you shift perfectly. That's extremely difficult to do.

Clutchless upshifting is theoretically easy, but in reality I find blipping the throttle on a downshift to make for an easier rev-match.

However, 99.999% of people who try to shift a conventional helical-geared synchromesh gearbox (e.g. every production car made today) without the clutch are NOT going to do it right, and they are going to bang the gears around and increase the wear. I personally recommend they replace a $150 clutch disc (or $250-450 if they wear out the whole assembly too) rather than a $800+ transmission rebuild. :p

On a transmission with straight-cut (dog-cut) gears, clutchless shifting is easier and considerably less damaging, but it still has to be done properly.

I don't know about 2nd gear always being first to go, in many newer transmissions, 3rd gear is actually the weak like. The Aisin-built 6-speed boxes in both the Mitsubishi Evo8/Evo9 MR-trim tends to fragment 3rd gear as low as 300whp, and in the B13 (91-94) Sentra SE-Rs, 5th gear's syncho and shift fork tend to wear out first, resulting in 5th-gear-pop-out.
Clearly you don't understand how a manual tranny works. The gears are ALWAYS syncronized. There is a collar around several shafts in a transmission and when you move the shift lever it moves the shifting fork which slides that collar towards the syncronizer which matches the speed of the collar dog teeth with the female holes in the side of the gear itself. Just look up manual transmission at www.howstuffworks.com for a visual diagram and flash animations of how a transmission works.

BTW, it doesn't matter how the gears are cut, they are always meshed together.

Edit: There is one input shaft and one output shaft. By sliding a collar one 2-4 shafts determines which gears will be turned by input shaft and thus, changing the gear ratio. Go to www.howstuffworks.com It will make more sense.

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Post by ciz28 » Sat Jun 02, 2007 3:43 pm

I know it's not exactly comparable, but clutchless upshifting is really easy on my GSX-R600 motorcycle with a slipper clutch. I don't know the mechanics behind it, but I'd be all ears if someone wanted to explain the details for me :D

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Post by chinna_n » Tue Jun 19, 2007 9:47 pm

continuum wrote:It only does no additional wear if you shift perfectly. That's extremely difficult to do.

Clutchless upshifting is theoretically easy, but in reality I find blipping the throttle on a downshift to make for an easier rev-match.

However, 99.999% of people who try to shift a conventional helical-geared synchromesh gearbox (e.g. every production car made today) without the clutch are NOT going to do it right, and they are going to bang the gears around and increase the wear. I personally recommend they replace a $150 clutch disc (or $250-450 if they wear out the whole assembly too) rather than a $800+ transmission rebuild. :p

On a transmission with straight-cut (dog-cut) gears, clutchless shifting is easier and considerably less damaging, but it still has to be done properly.

.
Hmm, I am not sure how it differs between helical gears vs straight spur gears, because all of these are constant mesh gears. It means, the gear pairs are always meshed with each other. It is the synchronizer which selects which gear set output is transmitted to output shaft. Just checked wiki to confirm if anything changed since last 15 years.
Ref: http://en.wikipedia.org/wiki/Manual_tra ... ansmission

Typical shifting without using clutch generally takes toll on synchronizers, mostly anyways.

I would not advise to shift the transmission without using clutch from stand still, but it is okay when vehicle is in motion. So, use clutch for the 1st gear, once you attained the shifting speed for next gear, pull the gear lever to neutral then let the engine RPM dropdown to match the output shaft speed( you will know by practise or observe the tachometer while driving the with clutch), the move the gear selector to the desired gear, don't push it hard, give synchronizers time to match the speed, it should smoothly shift into the gear. While downshifting you need to revup the engine( little more careful) and match the gear.

I used to drive my Diesel Jeep quite frequently without using clutch(mostly when I am tired of longday by the evening). Never had a gearbox problem. I also used to shift without clutch on heavy 10+ ton diesel trucks, but I only used drive these when none of our drivers show up.

Ofcourse I used to do it pretty much daily on my Yamaha(except the 1st gear).

Also double de-clutching very good practice esp for downshifting. It reduces the strain on clutch gearbox and drive shaft a lot.

Anyways, when I first dismantled the gearbox in Engineering lab, I was puzzled with all these synchronizers all that stuff. Why can't they simply slide the gears!!? And differential was a puzzle too. Ofcourse now we all know how these things works, and why they are needed.
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Post by tehfire » Tue Jun 19, 2007 10:13 pm

I've only dry-shifted my Kawi once, and that was on accident (I think from 3rd to 4th or something like that) and I was really surprised at how smooth the transition was. Either than transmission is amazing or I got really lucky. Is there any real advantage (or damage) to dry-shifting a bike?

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Post by chinna_n » Wed Jun 20, 2007 8:32 am

tehfire wrote:I've only dry-shifted my Kawi once, and that was on accident (I think from 3rd to 4th or something like that) and I was really surprised at how smooth the transition was. Either than transmission is amazing or I got really lucky. Is there any real advantage (or damage) to dry-shifting a bike?
Nothing substantial, I guess, just you do not need to press clutch, good for lazy guys like me. In theory you should be able to extend the life of the clutch, but if you use your clutch properly, clutch pretty much lasts life of the vehicle. Many people ride on the clutch, and thats why clucth worns out quickly.

In general bikes have multi-plate wet clutches vs big dry single plate clutch in cars and trucks. The multi-plate wet clutch( it is immersed in oil in the gearbox) typically can take more abuse than dry single plate clutch. I heard quite few times on cartalk about people who burned clutch in 100 miles( that is right 100 miles) in a car. That's highly unlikely( almost impossible) in the case of bike( ofcourse with multi-plate wet) in 100 miles.

Anyways irrespective of whether you use clucth or not, it is always good for the tranmission to match the engine and tranmission speeds for that gear, for both upshifting, and down shifting.

BTW, I never had to replace clutch or clutch plates in any of vehicles I used/owned. But now, there is no need to, as pretty much every one in US uses auto. If not for you, you need to have it with autotranmission for wife.

EDIT: I forgot to mention, unlike cars, Bike transmission gearshift pattern is sequential. That means to go to 5th gear you need to go thru 2-3-4 etc, and there is no neutral in-between(unless there is some false neutral), so it is not as easy car to do a clutch-less shift. Typically many bikes have neutral between 1st and 2nd ( or even before 1st gear), so it is easy to do it for the 2nd gear, but remaining gears you need lot of practice to shift smoothly( make sure no torque transmitted while shifting).

Ofcourse there are some exception, where few old bikes( may be some new) used to have universal neutral, so you can bring to neutral from any gear and shift to any gear directly. Some have 2 neutrals( between 1 -2 and 3-4). So you better be careful with bikes as you do not get a chance to match the engine and tranmission speeds.
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