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I have been driving stick for 15 years and within the last year I learned I can shift gear without the clutch.

Normally the transmission will not let me shift gears without using the clutch. However, if I hit the right RPM, my stick will let me shift into the new gear without any resistance. Why does this work and is there a downside?

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You can do this if your engine RPM, the speed of the vehicle, and the gear you are shifting to/from is just right. The reason you can do this is because you have synchros in the transmission which allows the two gears to match rotational speeds as they come in contact (basically, there is more to it than this, but hopefully you get the drift). The synchros are sacrificial in that as they are designed to wear out before the gears get worn. When you perform clutchless shifting, you are creating a large amount of unneeded wear on your synchros. By wearing these out, you'll be required to rebuild your transmission sooner than by utilizing normal shifting methods. With the clutchless method you are using, you are causing these the synchros to attempt to mesh until the correct rpm is met, even if it is for a short period of time. This is where the wear will occur. Even if it is a short period of time, there is just about no way you can hit this exact every time. If you feel that you are, you are more than likely fooling yourself. Any resistance during the shift is unneeded wear on the synchros.

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    Ah. That's what I am experiencing. I should still rev to match rpm, but I should also use the clutch to minimize wear. – Nelson Feb 23 '15 at 23:03
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    As an addendum to this, clutchless shifting is very common in big-rig trucks that don't have synchronized gearboxes (from my understanding, they don't really use the clutch outside of launching in first gear. – Shamtam Feb 24 '15 at 3:32
  • While this is correct for the vast majority of situations, for various racing scenarios you learn a skill which removes the wear on the synchros, and that is rev matching as you hit neutral on the gear change. This is most useful on downshifting as it is fast - you don't need to wait for the synchro to spin up. Done correctly it can make a heel-and-toe downshift completely smooth. It does take a lot of practice though. – Rory Alsop Feb 24 '15 at 8:19
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    Performance bikes usually have spurr gears instead of helical, don't use synchros and have dog gears that can take a bit of beating. Regardless, you can quickshift by applying a gentle pressure to the shifter proceeded by quickly closing the throttle/ignition kill module to let the gear automatically upshift. This works well for upshifts only – chilljeet Feb 24 '15 at 10:25
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Gears for gearboxes are usually spur gears (noisy but stronger) and / or helical gears (silent but weaker). If there are any others I haven't heard of them.

With spur gears, and only once you are in motion, you can do a clutch-less shift relatively easy, especially if you match the correct RPM. This would do a bit of additional wear on the gearbox. The good news is you are not wearing out the clutch & clutch bearing if you make a clutch-less shift. It is up to you which you will wear out.

With helical gears, it is also possible to do clutch-less shifts but again, only in motion. But, unlike spur gears, you will feel some resistance and hear noises. All of which are pointing out the additional wear you are creating in the gearbox (much more than with spur gears).

If I were you I would not even think about doing that in this case, severe damage to your transmission may occur. Of course you can do that if you are in danger, but forget it in your daily driving.

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    I'm not sure this answer is entirely satisfactory. Firstly, from what I have learned practically every manual transmission has helical gears for forward gears and spur gear for reverse. Also, as far as I understand it, the forward gears are continuously engaged and locked with a dog collar. There are synchronizers allowing dog collar engagement even if the speeds are not matched. So, if you hear noises, the dog collars are wearing, and if you feel resistance during shifting, the synchronizers are wearing. – juhist Dec 25 '15 at 20:22
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There's a LOT of misinformation floating around this page.

First of all, whether a gearbox has spur or helical gears has nothing to do with the actual shifting between gear ratios. In a constant mesh gearbox (essentially every automotive manual transmission), the gears are always engaged and all spinning. The difference between a racing transmission (or motorcycle trans) and a common road going manual is the way by which the gears are selected. A racing transmission uses dogs (hence dogbox, or crashbox) instead of synchronizers. Look up a diagram if this is confusing.

Basically, a dogbox allows instantaneous shifting without the clutch, but in a synchro box you have to put it in neutral, then match revs, then engage next gear. In a synchronized box, it is unnecessary to shift without a clutch (unless, for instance, your clutch is broken and you need to limp the car home/to a shop). This will result in increased synchro wear

  • Your comment of "In a synchronized box, it is unnecessary to shift without a clutch" is a curious statement. Could you write this without the double negative so it becomes clear instead of convoluted? – Pᴀᴜʟsᴛᴇʀ2 Jan 28 '17 at 15:05
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While you are somewhat correct most production cars only use helical gars for foward gears mostly because spur gears are loud and customers would complain.. But for any type of performance transmission used for racing or because you want them can have all spur gears.. And shifting without a clutch on spur gears is completely ok it's called bang shifting, basically yanking shifter into next gear without really lifting, most circle track cars do this. And because you are using it for some type of performance use of course you will need to be rebuilding it more often.

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I don't see the double negative that Paulster 2 seems to read. "In a synchronized box, it is unnecessary to shift without a clutch."

That is a true statement. I don't think it could be any clearer. Some drivers, especially those driving large and heavy trucks, feel like they're saving time and shifting quicker if they float gears. Most of them are driving trucks that aren't theirs, so they have no stake in treating it kindly. Terrible attitude, but that's the way it is these days. I'm old school, and I was taught to take care of that which is not mine simply because it's not mine.. They seem to forget that the big rig they're thrashing the gearbox in is a tool to get two jobs done; one, to move freight, and the other to make a living. If the truck goes down for a transmission failure, no freight gets moved and the driver with the bad habit gets no pay. Some drivers think clutches are for sissies. This is twenty years and almost two million miles of hauling fresh produce across the country and another twenty years of working on man-rated space hardware (specifically proof testing almost every part of the Space Shuttle Main Engines) talking. I'm so glad I never learned how to float gears.

If the shift is well-coordinated, that is, timed well, using the clutch will create a seamless, smooth gear change that can outperform any automatic transmission. One has to listen to the feedback the truck is giving. The trick is to learn what the drivetrain wants and then give it. Too many drivers fight the truck and try to beat it into submission. That's like beating the donkey because you overloaded the cart. The transmission will tell you when the timing is right, just like it'll tell you when you're wrong. It's a rhythm, and with or without the clutch the gear change can't be made unless everything is rotationally ready. The purpose of the clutch is to assist in achieving synchronization of the rotating parts and greatly reducing wear. The operator still has to learn the correct timing of the gear change, upshift or downshift. Once that is achieved, therein lies the pride and satisfaction of a job well done, without any wear on the gearbox or clutch or any other drivetrain part.

Use the clutch, Luke.

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the last answer was almost tits. i may be older school. i was taught to double clutch. i cringe if gears are ground. after a while you wont need the clutch- that is if you don't develop the bad habit of floating as the primary technique. this is where i slightly disagree with previous the previous answer. beginning drivers have to float (unless you want them to come to a stop and start over-mindless of traffic) to catch a gear, ANY GEAR! It is the only way the truck will stay moving down the road. some, maybe most, of those drivers that continue to float gears are not necessarily unconcerned about the life of the transmission but are just more concerned with not missing a gear because they will get lost and have to select down and SINK it into 5th... or worse.They never learned and probably never will. Once you start listening to turbo resonance instead of the transmission gears you will KNOW when to shift. at least with a 10spd anyways. this i know very well. i ruined my clutch brake within the first two months of driving in 2007. ive never changed it yet.never had a transmission issue in 400,000 miles so far. just log book violations.

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