the slip: shifting without using the clutch
 

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.

shifting without using the clutch #1

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

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!

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.

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.

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.

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.

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

By upshifting, I take it you mean going from 2nd, to 3rd, to 4th, to 5th etc.

Don't you mean downshifting is tricker without using the clutch?

LOL, ok, my dyslexia kicked in again. I got it backwards. Upshifting is the easy one, downshifting is trickier, I'll edit it.

Once again I fail to see how it saves fuel.

lets say I'm driving and its time to up shift from second to third. I start out with the engine at a high rpm. After I shift, my engine is at a lower rpm.

Shifting with the clutch I take some of the high rpm rotational energy and, even though the clutch slips some, use it to generate torque to move the car forward. The rest of the energy gets turned to heat.

Shifting with out the clutch I pop it out of gear at a high rpm and let the engine spin down (wasting energy that could be used) until the syncros line up and pop it into the next gear.

Learn it in a 38 Ford truck with straight cut gears and no synchros, and you will have it down pat.

1st to 4th back to 1st in my M22 4 speed 59 Corvette with no clutch. Heck I drove it to work with the steering gear failing and it would only turn right. Left turn, you went through the intersection and backed up with the wheel to the right then foreward.

regards
Mech

With a modern engine, while the engine is coasting down, you would use no fuel since DFCO would likely cut off the fuel The fact that a modern engine uses no fuel when coasting negates your argument. But regardless, the amount of fuel saved for that simple method of changing gears would be crazy small compared to the driving style shifting without the cltuch encourages compared to the driving style of the clutch fiend.

DFCO only works when decelerating with the clutch engaged. If you shift to neutral or as soon as you push in (disengage) the clutch, fuel has to flow or the engine would quit.

I know how to clutchless shift but I don't do it regularly- except when tossing it into neutral for glides- and I don't see any potential for fuel savings either. On the "Pro" column it forces the driver to be more consciencous and smooth; on the "Con" column I do believe, even when smoothly executed, trans wear would be increased while fuel saved would be nothing.

I use clutchless shifting when I'm using my left knee to steer because I'm eating and texting with my hands. It is very important to know how to do. ;)

I'm talking about the fuel already used to accelerate the engine to the high rpm before the shift. The fact that no more fuel is used does not recover any energy that has been expended. Just letting this useful energy dissipate is a waste.
Hogwash!
No utilizing all opportunities to recover energy saves fuel. Popping the clutch burns the clutch not the fuel. The clutch was designed to wear, gears are not. Save fuel and your transmission by using the clutch.

That would only occur shifting down.

The shifting without clutch would be primarily used shifting up and then EOC.

So you're saying don't use the clutch, use the clutch?

Had a 250 cubic inch '70 C-10 manual. Getting that '3 on the tree' manual column to shift was hard enough using the clutch. 2nd to 3rd would work without the clutch but 1st to 2nd, forget it. Truck was about as bare bones as they get. Drum brakes, manual shift, no radio, 3 speed on the column, manual windows and door locks.

Don't use the clutch in my 5 spd diesel truck. Use a 2-4 skip shift for upshifts no clutch. Seems to slide in 4th gear easy. For the RX7 it's 1 to 3 without the clutch then to 4th or 5th depending on the speed limit. Still use the clutch with the cycle but it's still new. Need to get a feel for it first.
VT247

What proof is there that properly shifting without the clutch increases wear on the transmission? I've yet to talk to anyone that said he used to shift without a clutch, but then it wore out his transmission, so he stopped doing it.

Its not when you do it properly. Its when you screw up which is bound to happen.

Bingo... kinda like doing a DFCO in neutral and losing vacuum on your power brakes, then plowing thru an intersection on a red light. Almost did that a couple times. Next car I DFCO in neutral will be designed for it (no vacuum booster, disabled steering wheel lock mechanism).

IMO, until you've truly foolproofed it, some things are just best not doing since the potential risks are greater than the benefits.

I've been wondering why the steering wheel locks. Is that difficult to disable?

It's real simple.

Don't turn the key to the locked position.

Between locked and on is a position that keep the wheel unlocked, and only turns off the electrics. So go to that one.

I agree. I'd certainly recommend practicing this on a beater. And I wouldn't recommend this for people who have no interest in mechanics and could care less for where the revs are likely to be close to for a certain gear at a certain speed. But then again, such people are likely to be uninterested in a stick shift to begin with.

the mechanisms are in the steering column and, depending on the car, dictates the level of complication one must go through to disable it.

I don't use the clutch when upshifting my motorcycles. It is very smooth and faster than using it. I use the clutch for downshifting generally. I have shifted my manual shift cars without the clutch but I think it is generally less smooth.

I would like to have a double clutch manual shift transmission although I have never tried one.

Learned to slip shift today. Tried to be gentle, little bit of clunking here and there. Fifth seems to be hardest to get into. It was the only gear I ever got any screeching from. As soon as I hear that I back off and use the clutch. It was also the only gear I wasn't able to get into perfectly smooth.

Any tips? Am I more likely having timing problems or do I need to get in just the right spot side-to-side with the shifter or something?

I asked one of the diesel mechanics here about it -
If you shift properly, there's not one tiny bit of difference using the clutch vs not using the clutch for fuel economy. note this is on big rigs, where to downshift you have to rev the engine up in neutral even when using the clutch - and rolling in neutral is a good way to get yourself killed in a big rig, so that question never came up, although the trucker term for it is Georgia Overdrive or sometimes Mexican overdrive. Gotta be on some serious medication to try that...(in a semi)

he went on to say that while you could make a case that you were causing less wear and tear on the clutch, that one shift you miss will cause 100 times the wear that a lifetime of using the clutch would cause.


I do not know if this part applies to cars - he also gave me a very strong warning against rolling down a hill in gear with the clutch depressed. He told me that due to the multiple reductions involved and no pressure on the clutch, it can actually cause the clutch to explode and send shrapnel through the cab of the truck

I'll admit to being quite guilty of not using the clutch when shifting especially in the low range gears :) Dont tell anyone. lol

Also, I think one of the most overlooked ways of saving fuel economy on a vehicle witha stick shift - don't rev the engine up to get going, ESPECIALLY if you have a computer controlled car. GENTLY ease up on the clutch, and once it is all the way up and you're rolling, THEN give it gas. Doing the gas and clutch at the same time wastes a lot of energy as heat.

That's how you stall. I guess unless your engine is a big V8.

I routinely did it with a 1999 Rav4 with a 4 cylinder engine - it took a bit longer to get rolling that way but it never stalled.

Winki
For some reason my vw diesel 1.6 can actually go without throttle from a dead stop. I do use the clutch of course. For some reason there is a lot of low end torque and maybe a lot of flywheel. It is a curious little car.

Most computers will automatically throttle up a bit to try to prevent a stall. However, on an engine with not much low end torque, it's a bad idea, as you end up slipping the clutch far more to get moving.

It was a technique taught in truck driving school in the driving semis for fuel efficiency class that I never believed would work in a car either - until I tried it. Basically, you let halfway up on the clutch, let the vehicle start rolling, then let all the way up on the clutch then give it gas after the clutch is all the way up. They said it cuts down on clutch wear too. It was still on its original clutch at 157,000 miles when I traded it in for a Ford Ranger, and I wasn't exactly an easy driver on that old Rav4 either.

Comptiger,
The less power (and heat) that the clutch has to adsorb the less it wears and the less fuel you will use to get started. Cost to implement is zero as well.

I have a related question.

When trying to rev match to engine brake, is coming in with rpms a little low or rpms a little high better in terms of wear and tear on the clutch/transmission?

I'd say coming in a little high is probably better for wear, as the revs are already falling as it engages, vs the clutch having to pull them up against engine braking.

Oh no, I can easily just lift foot from clutch and car gets going, while finding parking spot I don't touch accelerator at all, same with when taking off, I just lift foot off from clutch.

Mine is 1.9l diesel, but have been doing this with 2.0l gasoline motor too in my other car.

Modern cars will stall unless they have stupid automatic throttle control, which will add more throttle, modern cars have very thin torque at idle, when older engines have strong good torque at idle.

That is at least how it is in euro cars.