Halx

So.. what happens when I step on the clutch?
Where is that sweet spot where the gas starts picking up in 1st gear?
I know it's different from car to car, but what are the mechanics behind it?
How is it possible to shift without the clutch?

Is someone informed enough to explain this all?

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Cynthetiq

google is your friend...

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How does the funny "H" pattern that I am moving this shift knob through have any relation to the gears inside the transmission? What is moving inside the transmission when I move the shifter?
When I mess up and hear that horrible grinding sound, what is actually grinding?
What would happen if I were to accidentally shift into reverse while I am speeding down the

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Halx

i thought of howstuffworks before.. i just forgot to check before posting this.. whoops!

thanks though.. it's a great lesson

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irseg

Basically there are two flat metal plates -- one on the engine (the flywheel) and the other on the transmission (the pressure plate). Sandwiched in between these is clutch disc, which is covered with brake pad-like material. The middle of the disc has a hole in it, which connects to the input shaft of the transmission. When you press the clutch, the two outer plates are forced apart. When you let off the clutch, the two plates move back together, squeezing the pressure plate and forcing it to rotate the input shaft. The "sweet spot" happens when the clutch disc is starting to turn the input shaft, but the friction material is still slipping between the two plates.

As for shifting without the clutch, basically you have to match the speed of the input shaft with that of the gears turning inside. I can do it pretty easily with my T-Bird by giving it just enough gas that it's not accelerating, but the engine isn't slowing the car down either. It's tricky but once you figure out how to do that you can just slide it out of gear and into the next one pretty easily. That only works for upshifts though, I haven't mastered clutchless downshifting. And I can still shift faster using the clutch, basically it's just something cool to show to your friends or if you're having a lazy moment and don't feel like moving your left foot.

Halx

Nice. Thanks.

How about tricks and tips with the clutch. There is definately a range of "GOOD" and "BAD" clutch driving. What can a manual driver do or pay attention to in order to properly operate his transmission for the best life and/or performance?

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DEI37

Don't slip it. YOu might a little bit on take-off, especially on a hill, but with practice, you'll figure out exactly what it takes so the car doesn't roll back much, if at all, even on the steepest of inclines. NEVER use the clutch to keep you from rolling back. That's the QUICKEST way to burn one up.

You know all those nice smooth shifts that todays automatics make? Try to do that with a manual trans, and you'll roast a clutch in short order. Treat the clutch as a switch. It's either on or off. It will make shifts a little harsher, but actually, over time, you'll figure out what it takes to use the clutch as a switch, AND make reasonably smooth shifts.

Any more questions...just ask...we'll answer.

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End User

I've been told to avoid downshifting to slow the car down (eg. Shifting from 4th, to 3rd to 2nd to decrease your speed), which makes sense I guess.
Your brakes cost alot less to replace than your gearbox and various drivetrain components.
Never change gears without using the clutch. Your left foot should not be doing something so important that you cannot press the clutch.
If you drive an older model manual, learn to double clutch. Your synchros will thank you for it.

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89transam

what is double clutching

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MSD

1 Shift into neutral

2 Rev engine (for downshift) or let it rev down (upshift) to where the RPM that the enging will be at for current speed in the next gear

3 Shift into next gear

You use the clutch twice, hence the name "double-clutching.) It reduces the amount of work the synchros do, and makes them last longer.

Power shifting is the same, but without using the clutch at all. Do not do this. I don't care how good you are at driving and shifting, don't do it. I'll laugh at you when you suddenly find that you can't shift into third because the teeth on the collar don't line up with the holes in the gear anymore.

Peryn

Well, for long clutch life, realize when it wears and you can pretty much figure out how to make it last on your own. The only time the clutch material really wears at all, is when it is only partially engaged. When engages, the flywheel and pressureplate/input shaft are locked together. The clutch is stationary on them, and the whole assembly is turning. The clutch material, is therefore not being worn. When it is fully disengaged (petal to the floor) nothing is really touching it, so naturally it wont be wearing down. At any point in between though, when it is touching the rotating engine parts, and not locking them together, you are wearing down the clutch. So slowly taking off, your clutch is spending more time with the engine moving fast, and the clutch not moving as fast. Kinda acts like sandpaper and wears away the clutch lining. Where as if you drop the clutch quickly, while you stand a chance of shattering the clutch if its mega-fast, there is essentially no time in there for the clutch to spin off its coating.

If it helps, think of it just like brake pads and rotors. When your foot is off the brakes, they aren't being used because they aren't touching the rotor (flywheel), and basically wont wear down. When you are stopped, and the pads are clamped all the way down on the stopped rotors, neither is moving (when the clutch is engaged and you are moving...parts are "stuck" to each other). Your brake rotors aren't turning inside the pads, so again, neither is wearing down. It is only in the process of doing the braking - some point where the pads are clamping down, but not stopped totally - that you wear them out. This is just like your clutch. It only wears the lining (very similar to that of your brake pads actually) when its partially engaged/disengaged, but not at the extremes. Now that you know when/how it wears, you can judge how to drive for long life. Quick engage/disengage of the clutch wont wear as fast, but puts a little more shock and abuse onto the other parts. Holding yourself at a hill with the clutch is like driving with your brakes on...its just gonna wear them VERY quickly. Taking a long time to engage the clutch just increases the time its wearing down (which is why 2nd and 3rd gear starts tend to be so hard on clutches).

As for not downshifting and using the engine to slow you down...it depends on how you do it. If you just engage the clutch in the lower gear, and let that spin the engine up, then yes, it is bad for the car and clutch. BUT, if you can spin the engine (flywheel) up to the same speed the input shaft of the transmission, there (theoretically) will be zero clutch wear. If you tap the gas after shifting down, before letting the clutch in, you can rev one side of the sandwich (flywheel, clutch, pressure plate) up to match the other side. Then when you put them together, there isn't a difference in speed, and nothing wears as they go together. When done properly, you shouldn't feel any jerking or engine revving while engaging the clutch. Once the engine and tranny are locked together, you can let off the gas and let the engine help slow the car down without any problems.

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merkerguitars

I don't believe that a bit......on my motorcycles I do this all the time (one older triumph and a yamaha) and I haven't blown out the gearbox yet....every mechanic I have known says downshifting doesn't hurt.

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grumpyolddude

Oh, that third pedal... the one on the left... is NOT a footrest! Get off of it if you ain't shifting. Saves wear and tear.

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End User

Meh. Cars and bikes are totally different breeds.

coventryblack

On most modern transmissions all gears except first have a syncro (short for syncromesh) ahead of the each gear. This helps you as you are shifting up but it is especially important for downshifting. Before syncros, one had to double clutch to properly match the engine rpms to the transmission, or force the gear and damage the tranny. In certain cars, if you downshift frequently they'll wear out fast. But in better trannies you won't have a problem. I can't imagine life without downshifting.

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stingc

I've never understood why people like to downshift to bring the car to a complete stop (slowing down I get). Isn't it a lot simpler, quieter, and smoother to just press the brake?

jwoody

Your brake pads will last a lot longer if you downshift to slow down, especially when driving down steep hills.

And you can't use the gears to stop completely, the car would just jerk a bit then stall.

When you take your driving test in England, if you don't downshift to slowdown you'll probably fail. "Overuse of the brake" is the term they use.

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yakimushi

I downshift religiously and I haven't bought brake pads for almost five years.

I did have the rotors replaced though...

My clutch is the original, the car has 165000 miles. Its all in the driver!

stingc

I understand that you can't completely stop with downshifting. I meant that some people see a light turn red, do a couple of downshifts, and then brake.

Cars with automatics always use brakes only, and don't have the brake pads wearing out much. Brake pads are really cheap too.

(I do downshift when going down hills, just not when I know I'm going to a complete stop on level ground)

Peryn

Brake pads ARE really cheap, but automatics actually usually go through them faster, and FWD automatics tend to eat them like crazy it seems.

Automatics dont necesarily have to ONLY use brakes. They can manually change gears (i.e. the 3 and 2 gears on the shifter), or some have a "hold" button or something similar, which holds them in their current gear. They can downshift, press hold, and then use engine braking as well. *I* dont, but a lot of people actually to downshift in automatics.

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BoomTruck

Clutchless shifting is best learned on an unsynchronized 13 speed. Then doing it properly on any transmission is a breeze.

Car transmissions don't lend themselves too well to clutchless shifting. The more rotating mass in there, the better it works.

If you ask someone that drives a heavy truck how often they use the clutch, you will often hear "Once when I start, and once when I stop".


And downshifting has it's proper uses. Dropping it into second at 40 MPH because it "makes the car sound badasser" is NOT one of them.

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Sion

clutchless upshifting, on either a car or motorcycle, is a good habit to have. once you know how to do it correctly, it has two advantages: first, less wear and tear on the clutch; second, faster shifting and less loss of engine rpm, thus you retain more speed during the shift.

clutchless downshifting is a BAD idea. period, end of story.


downshifting (with clutch) to slow down is a good idea, if done correctly. and in certain circumstances, like many types of racing, or in the case of brake fade/spongy pedal/catastrophic brake failure, it is a necessity.


double clutching is essentially pointless on most modern manual transmissions.

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