- First gear, second gear, fourth gear, sixth, eighth, twelfth gear. (engine revving) We're talking about manual transmission. You probably know the basic idea. The transmission changes the gear ratio to make sure you're
getting the optimum power from your engine to the wheels. When two gears are in mesh, an almost lossless
transfer of power occurs. In this case, a force is
applied to the gear on the left, which is in turn moving
the gear on the right. For every revolution
the left gear completes, the right gear completes one
in the opposite direction and with equal force. Pretty straightforward. What makes gears truly useful though is when they aren't the same size. Let's shrink that driving
gear down by half. Now it has to complete two rotations to move the right gear once. Well, that sucks. But wait a sec, the total amount of energy required to move the
second gear one revolution hasn't changed. But now the driving gear delivers
the same amount of energy over twice as many revolutions, meaning it requires
half the amount of force at any given moment. It's like climbing stairs. Make the steps smaller
and each step's easier, but you gotta take twice as many. We've all ridden bikes, so you know what it does. But how does it work? A standard manual transmission is made up of an engine
shaft or input shaft, and that's the side that
comes from the engine. A drive shaft or output shaft, that's the side that
goes to the drive wheels, and here, underneath both of those, is the counter shaft. And on these shafts are the gears. - How familiar are you
with the gear wars exactly? - All of this has to do with getting the right amount
of torque to the wheel. If you like learning about torque, check out our Science Garage
on torque and horsepower. If you want to know about
toque and hose powder, ask a Canadian. (speaking in foreign language) But let's get back to the gears. - Okay, it was about 754 years ago. - If I turn the input shaft, the gear on that turns this counter shaft, and that turns all of the
gears on the output shaft. But all these gears are
moving at different speeds. When the gears aren't engaged, they spin freely from the output shaft because they're not anchored to it. Only one gear at a time is
spinning the output shaft, and that's because of what is
anchored to the output shaft, these hubs. Around these hubs are sleeves. These sleeves slide over
the teeth on the gear and anchor them to the hub
to drive the output shaft. But wait, there's more. Look at those tiny little teeth. Matching up those tiny teeth
at the edge of our gear with the sleeves' tiny teeth. Well, that's almost impossible. So between them are these synchronizers. We cut the power to the counter shaft, let the wheels drive the
output shaft for a change, and when we push the synchronizer ring, it gets squeezed against our gear and locks it to the hub, so it's anchored to the output shaft. That's why when you're shifting, you get that uh-uh. (engine revving) Now the wheels in the drive
shaft and the counter shaft are all spinning in mesh. Voila, we've shifted gears. Some manual five-speed transmissions may have minor differences here or there. This is pretty standard for the most part. The big gear here, which is enmeshed with the smallest gear in the
counter shaft is first gear. First gear is always gonna be the largest gear in the transmission, producing more torque for the back wheel. It's taking a lot of fast turning force and making one big slow turning force. The slightly smaller gear
next to that's second. Then goes third and smallest one's fourth. On most four- and
five-speed transmissions, fourth gear is what's called direct drive, or a one-to-one gear ratio, meaning the input and output are turning at the same rate of speed. Okay, let's pop the shift
fork into first gear and engage that big ol'
gear here in the front. In first, this particular transmission's got a gear ratio of 3.83 to one, so I can turn the input, one, two, three in exactly 0.8 times, and you can see the
output has turned once. That's torque, baby. Pop it into second, and the gear ratio on
this guy's 2.062 to one. Third gear is 1.4 to one. You know the drill. One and .4 turns turns it one time. And then as we mentioned
earlier, fourth, one to one. They're turning at the same speed. That's gear ratios. Guys, we did it. (children cheering) Now a lot of you are probably saying what about fifth gear? We're getting there. Fifth gear is kinda
hidden in the back here, and we call it overdrive. Remember how first or third
gear were high gear ratios? Well, get ready for a low
gear ratio, buddy boy. In fifth gear, I only need
to turn this shaft .8 times to get a full turn on the output. That's overdrive, which gets
mucho better fuel economy. At this point, you're getting power from the forward momentum of your vehicle and don't need as much power going to your engine or your wheels. Some six- and seven-speed
cars can have double overdrive for even better fuel economy
at those high, high speeds. Oh, reverse is over here. Boop, boop, boop. It hits this gear, it
makes your drive shaft spin the same direction
as your counter shaft. Now here's the rub. The drive shaft's attached
to the wheels, remember? When we shift gears, the
wheels are gonna want to spin the counter shaft
at a different speed than the engine's trying to spin it. We have to take that power off somewhere, or it'll make a grinding sound, like when your brother's robot hamster won't stop body shaming you so you throw it in the blender with all the bad forks and spoons and press puree to teach it a lesson. So where do we let all
that spinning energy go? The clutch. The clutch looks like this. The clutch has a disc with a high friction
material on both sides. The engine is actually
driving the flywheel. And the input shaft to the transmission is mounted to the disc. When the disc is pressed
firmly against the flywheel, it catches and can drive the shaft. In the case of this clutch, it's squeezed by these springs and attached to a pressure disc and anchored by this pressure plate, which gets bolted to the flywheel. Most clutches use three springs, but in performance
clutches you can have more. And that makes the
connection between the disc and the flywheel even
stronger and more effective in high torque application. Like racing. And this is where things
get a little tricky. A diaphragm spring is
connected to the pressure disc under the pressure plate. When you hit the clutch
it pushes the center of that diaphragm spring and
that pulls up on the springs, which lifts the friction
plate off the flywheel. Awesome. Now we've disengaged the
power from the shaft, but we let off the clutch pedal and re-engage the friction disc, you're gonna bang, pop right into action. We don't want that. We want to ease into the movement. So attached to the friction plate there's these other plates
with coil springs in them. These springs are attached to a hub and that plate is the one
that anchors the shaft, and that goes to the transmission. Those springs absorb
the jolt of re-engaging the friction plate to take a little stress off the other parts of your drive train. You want to try to get on and off your clutch pretty quickly, or you might burn it out. (engine revving) That happens when the flywheel
and the friction plate rub together too much. It happens. Usually waiting on a hill
to get into a Dodgers game. (engine revving) So what is a double clutch? - Rarely shifting, not double
clutching like you should. - Well, it's not really two clutches. Double clutch is clutching twice. Once when you shift into neutral to hit the gas and match the engine revs to the gear you want to go into. Then you hit the clutch a second time to shift into that gear. I always use the double
clutch when I'm racing, drivin' big rigs, and dunking. ♪ I believe I can fly, whoo ♪ - Pretty cool. Thanks to honey for sponsoring this video. Honey is a browser extension that automatically scours the
inter webs for coupon codes to make sure you're gettin'
the best possible deal. Ya know how you always get to the checkout and it's like, do you
have a discount code? And you're like, uh, no? Well, say no no more. (children cheering) It's super easy to install. It's literally two clicks and it's free. You know how they say you gotta
spend money to make money? Well, that may be true, but you don't have to
spend money to save money 'cause honey costs you nothin'. I used it when I bought new rear struts. Honey just patiently sat in the background until I was ready to check out. And when I was, it found a code and saved me mucho moolah. Searching for codes
yourself is often fruitless. And it takes all kinds of math. Do I want free shipping or 20% off? Honey does all that for you. To make sure you're gettin'
the best deal out there. That means more money
for your dragons hatching from egg sculpture collection. (glass shatters and cat screeches) And if it doesn't find a coupon code, well, that's because there isn't one. So you can shop confidently knowing you got the best deal out there. There's no reason not to add
honey to your browser today. Like, now. It literally takes two clicks and costs you no money. Click the link below to
add honey to your browswer for free. Or if you'd rather, type in
joinhoney.com/sciencegarage. Honey. Click this yellow subscribe button so you never miss an
episode of Science Garage. Follow me @bidsbarto and
follow Donut @donutmedia. You like replacing your clutch, check out this video on turbos. You want to hear about a car with maybe the coolest transmission ever? Check it out on this Up
to Speed on Conigzig. Don't tell my wife I burned out the clutch and had to get it
repaired, it's expensive.
If anyone wants a less thorough explanation, but a little calmer