the slip: shifting without using the clutch

[j12piprius]

Ptero made this excellent post about how to master the slip, shifting with only light use of the clutch, eventually not needing to use it. His post is so inclusive it seems all is needed is to master the instructions.

Originally Posted by Ptero

For pulse and glide, you'll want to master the slip. Always be gentle. Ham-handed people should avoid learning the slip in their own cars. You can break off gear teeth if you get clumsy.

SLIP

Get a tach if you don't have one.
Go 65.
Make note of the exact rpm. e.g. 3070
Go 55.
Make note of the exact rpm. e.g, 2750

Now, at 65 mph, touch the clutch and shift into neutral.
Take your foot off the clutch and off the gas.
Your idle will drop to around 500 rpm.
Coast down to 57.
Now bring your rpm from 500 to 2750. Be steady and precise, no hunting up and down.
As you hold the rpm steady at 2750 and your speedometer drops from 56 to 55, quickly jab your clutch (just a little - NOT to the floor) and slip the stick into high. A good slip shift will not make any noise except for a little "snick".

This technique works for all speeds and all gears (upshifts require doubleclutching) but you have to memorize the match points. To learn match points in big trucks that I'm not familiar with, I cheat by pulling the shift lever lightly against the spinning gears. A light accelerator foot, with an eye on the tach, will find the match point. Little transmissions with synchros can make this hard to do.

Once you are good at this, you will find the clutch is unnecessary, as well as the tach. It's like playing a musical instrument.

shifting without using the clutch #1

[j12piprius]

Originally Posted by Ptero

Why didn't you double-clutch or float to synch? I wouldn't even consider wearing my synchros. Your synchros, which are brass, will last forever if you match your gears.

shifting without using the clutch #2

[dennyt]

I guess that would work if you like to idle while you're coasting... bo-ring!

[dennyt]

I've shifted without the clutch in standard cars (synchro type transmission), on motorcycles (dog type transmission) and in a nice little racecar with a motorcycle engine & gearbox.

Transmissions with dogs instead of synchros handle clutchless shifting quickly and efficiently, at the expense of noise and jerkiness. (Yes, Jerk is an actual engineering term).

With a synchro box, clutchless shifting is slower than using the clutch, and much more likely to damage the transmission.

I don't see the benefit to clutchless shifting with synchros. Sometimes I will ease the car out of gear without using the clutch, but not back into gear. My tranny has 218k on the ticker and it's not getting any younger!

[FastPlastic]

I shift without the clutch on my ZX7R Ninja all the time. If you do it right, she's just as smooth that way as with the clutch. Bumped up my MPG's just a tad too.

[ConnClark]

I don't see how this saves you any fuel.

[FastPlastic]

Originally Posted by ConnClark

I don't see how this saves you any fuel.

By slip shifting the time the engine isn't connected to the drive train is reduced to a split second. It also reduces shifting time so I'm in a higher gear sooner. We're not talking a giant increase, but it's there.

[ShadeTreeMech]

If you are slipping the clutch, you are turning energy from the engine into wasted heat. By shifting without the clutch, you're allowing the engine and transmission to synchonize without being forced to quickly change speeds.

The description given is slightly overly complicated. When changing without gears, it is easier to learn to upshift without gears first, before learning to downshift. On a motorcycle it is crazy easy, in a big rig it is standard practice, and in a car or small pickup it can be just as simple.

When upshifting, you would ease off the gas while pulling out of gear. In one movement, pull out of gear and try to put the stick in the desired next gear. The stick won't engage the gear until it is time. Wait for the engine to coast down, and when the revs match, with you putting gentle pressure on the stick in the direction of the desired gear, you'll feel it start to engage. Give it the push needed to fully engage, and there you go.

Downshifting is a bit trickier. It involves disengaging the current gear, revving the engine past where it needs to be for the next highest gear, then following the above mentioned step of allowing the engine to coast down to the correct rpms.

For those who fear damage to their transmission, it is possible, but you'll hear it grinding away. If you clutchless shift without any sound being made, no damage occured. You just used the design of the synchros to your advantage for the purpose for which they were intended. Even using the clutch, the input shaft is still spinning, and the synchros have to force the input shaft to rev match to engage the gears. An argument could be made that a person skilled at shifting without a clutch could put more miles on a transmission that one skilled at shifting with one.

Even if you don't use it daily, being able to clutchless shift can save you a tow bill. My clutch cable broke on a Chevy Spectrum I used to have. I had places to go, so I drove for about a tank of gas worth with no clutch. I would kill the engine and put the car in first at stops, then start the car in first to get going. This may sound a tall story, but I drove in downtown Colorado Springs during a heavy snowstorm without a clutch sucessfully, then drove from there to Aurora (about 90 miles on the interstate) to my uncle's house, where he repaired it for me. He told me my grandpa had to do the same thing with an old Dodge pickup pulling a 5th wheel through the middle of Denver once, and didn't have a problem. I asked him whether it hurts the transmission to shift without a clutch, and with him being a master mechanic, figured he would know. He thought a moment, then said as long as it doesn't make a sound when you shift, no. And if it does make a sound, as long as you don't try to force the synchros together for a long time, it won't hurt it.

I've driven every stick shift vehicle I've been in without the clutch, and except for a 67 Chevy C-10, none of them complained. It is easier to upshift when the revs are higher up to give yourself more time to complete the shift, but with practice you can "speed shift" without thinking about it. I actually found it easier to upshift without the clutch than with it, but I would use the clutch for downshifting since it was a bit less tricky.

[Ryland]

Shifting without a clutch just seems like a bad idea having had taken apart motorcycle transmissions and replacing automotive transmissions and driving vehicles that require you to double clutch, even if you don't feel it grinding it is still causing more wear to the syncros and to the bearings because it is putting a harsh sudden load, using the clutch takes all of the load off the moving gears, double clutching and matching the engine RPMs will also help in reducing wear but if you plan to drive fast enough that you feel you have to drive like this then please stay off the public road ways.

[ShadeTreeMech]

Originally Posted by Ryland

Shifting without a clutch just seems like a bad idea having had taken apart motorcycle transmissions and replacing automotive transmissions and driving vehicles that require you to double clutch,

How many of these were extensivelyshifted without a clutch? I suspect few of them, most people use the clutch everytime.

even if you don't feel it grinding it is still causing more wear to the syncros and to the bearings because it is putting a harsh sudden load,

If done correctly, there is no sudden harsh load. I've been able to upshift so smoothly there was no perceptible change in vehicle momentum.

using the clutch takes all of the load off the moving gears,

not true, the input shaft is still spinning, while it has less momentum by far than with the clutch engaged, there is still a load which has to be synched forceibly by the synchros.

double clutching and matching the engine RPMs will also help in reducing wear but if you plan to drive fast enough that you feel you have to drive like this then please stay off the public road ways.

not much a fan of downshifting without the clutch, I'm just not that good, and I'm not certain what benefit there is to double clutching.

I would say for those who aren't technically skillful and for whom details bore them, shifting without the clutch is a bad idea. For me, clutchless shifting on a motorcycle is as easy as pie and is actually quicker than using the clutch, while passenger vehicles are a bit trickier, but it can be done with practice and becomes a skill you pride yourself in. At the very least, having the knowledge to be able to do it should be mandatory drivers ed, even if it isn't practiced consistently.

I also know clutchless shifting to be slower in a passenger vehicle than using the clutch, and requires a bit more care, which encourages more careful driving and makes you preplan your shifts to avoid unnecessary shifting.

I think it helps you to be more attentive to the car as a machine, to making you work with it so that its design and your purposes for it coincide. To me, using the clutch everytime makes driving a manual more of a chore and less the joy it can be by at least eliminating upshift clutching. To be quite honest, I never watched the tachometer while shifting, but rather listened to the engine and learned how to do it by feel. The slight bit of excitement I get by commanding the little transmission to do my bidding with the clutch and stick is only amplified when I use only the stick. For those who know how, it is a skill they pride themselves in, and few say they wished they never had learned how to do it.

How to Clutchless Shift | eHow.com