{"id":63268,"date":"2017-04-05T14:56:37","date_gmt":"2017-04-05T19:56:37","guid":{"rendered":"http:\/\/www.artofmanliness.com\/?p=63268"},"modified":"2026-01-08T14:05:21","modified_gmt":"2026-01-08T20:05:21","slug":"gearhead-101-understanding-manual-transmission","status":"publish","type":"post","link":"https:\/\/beta.artofmanliness.com\/skills\/cars\/gearhead-101-understanding-manual-transmission\/","title":{"rendered":"Gearhead 101: Understanding Manual Transmission"},"content":{"rendered":"

\"Manual<\/p>\n

Welcome back to Gearhead 101<\/a> \u2014 a series on the basics of how cars work for the automotive neophytes out there.<\/em><\/p>\n

Because you read the Art of Manliness, you know how to drive a stick shift<\/a>. But do you know what\u2019s going on beneath the hood whenever you shift gears?<\/p>\n

No?<\/p>\n

Well, today\u2019s your lucky day!<\/p>\n

In this edition of Gearhead 101, we take a look at the ins and outs of how a manual transmission works. By the time you finish reading this piece, you should have a basic understanding of this vital part in your vehicle\u2019s drivetrain.<\/p>\n

Let\u2019s roll up our sleeves and get started.<\/p>\n

Note: Before you read how a transmission works, I highly recommend reviewing our Gearhead 101s on the ins and outs of engines<\/a> and drivetrains<\/a>.<\/em><\/p>\n

What Transmissions Do<\/h3>\n

Before we get into the specifics of how a manual transmission works, let\u2019s talk about what transmissions do in general.<\/p>\n

As discussed in our primer on how a car engine works<\/a>, the engine of your vehicle creates rotational power. To move the car, we need to transfer that rotational power to the wheels. That\u2019s what the car\u2019s drivetrain — of which the transmission is a part of — does.<\/p>\n

But there are a couple problems with power produced by an internal combustion engine. First, it only delivers usable power, or torque, within a certain range of engine speed (this range is called an engine\u2019s power band). Go too slow or too fast, and you don\u2019t get the optimal amount of torque to get the car moving. Second, cars often need more or less torque than what the engine can optimally provide within its power band.<\/p>\n

To understand the second problem, you need to understand the first problem. And to understand the first problem, you need to understand the difference between engine speed<\/em> and engine torque<\/em>.<\/p>\n

Engine speed is the rate at which the engine\u2019s crankshaft spins. This is measured in revolutions per minute (RPMs).<\/p>\n

Engine torque is how much twisting force the engine generates at its shaft for a particular speed of rotation.<\/p>\n

A car mechanic gave this nice analogy to understand the difference between engine speed and engine torque:<\/p>\n

Imagine you were an engine and you’re trying to drive a nail into a wall:<\/p>\n

Speed = How many times you hit the nail head in a minute.<\/p>\n

Torque = How hard you hit the nail every time.<\/p>\n

Think back to the last time you were hammering nails. If you were hammering really fast, you probably noticed that you weren\u2019t striking the nail with much force. What\u2019s more, you probably exhausted yourself from so much frantic swinging.<\/p>\n

Conversely, if you took your time between each swing, but made sure that each swing you did make was as hard as possible, you\u2019d drive the nail in with fewer swings, but it might take you a bit longer because you\u2019re not swinging at a steady tempo.<\/p>\n

Ideally, you\u2019d find a pace of hammering that allowed you to hit the nail head several times with a good amount of force with each swing without tiring yourself out. Not too fast, not too slow, but just <\/em>right.<\/p>\n

Well, we want our car’s engine to do the same thing. We want it to spin at the speed that allows it to deliver the needed torque without working so hard that it destroys itself. We need the engine to stay within its power band.<\/p>\n

If an engine is spinning below its power band, you won\u2019t have the torque you need to move the car forward. If it goes above its power band, torque starts dropping off and your engine starts sounding like it\u2019s about to break due to stress (sort of like what happens when you try hammering too fast — you hit the nail with less power and you get really, really tired). If you\u2019ve revved your engine until the tachometer gets into the red, you understand this concept viscerally. Your engine sounds like it\u2019s about to die, but you\u2019re not moving any faster.<\/p>\n

Okay, so you understand the need to keep a vehicle running in its power band so that it\u2019s working effectively.<\/p>\n

But that brings us to our second problem: cars need more or less torque in certain situations.<\/p>\n

For example, when you\u2019re starting a car at a standstill, you need a lot of power, or torque, to get the vehicle going. If you floor the gas pedal, you\u2019re going to make the engine\u2019s crankshaft spin really fast, causing the engine to go way above its power band, and possibly destroy itself in the process. And the kicker is you won\u2019t even move the car all that much because torque drops off on an engine as it goes above its power band. In this situation, we need a lot more torque, but to get that, we\u2019ve got to sacrifice some speed.<\/p>\n

Okay, what if you just press on the gas a wee tiny bit? Well, that\u2019s probably not going to cause the engine to spin fast enough to get into its power band in the first place so that it can deliver the torque to get the car moving.<\/p>\n

Let\u2019s take a look at another scenario: Let\u2019s say you\u2019ve got the car moving really fast, like when you\u2019re cruising on the freeway. You don\u2019t need to send as much power from the engine to the wheels, because the car is already moving at a brisk pace. Sheer momentum is doing a lot of the work. So you can let the engine spin at a higher speed without worrying as much about the amount of power being delivered to the wheels. We need more rotational speed<\/em> going to the wheels, and less rotational power<\/em>.<\/p>\n

What we need is some way to multiply the power produced by the engine when it\u2019s needed (starting from a standstill, going up a hill, etc.), but also decrease the amount of power sent from the engine when it isn\u2019t needed (going downhill or going really fast).<\/p>\n

Enter the transmission.<\/p>\n

The transmission ensures that your engine spins at an optimal rate (neither too slow or too fast) while simultaneously providing your wheels with the right amount of power they need to move and stop the car, no matter the situation you find yourself in.
\n<\/a>
\nIt\u2019s able to do this effective transmitting of power through a series of different sized gears that leverage the power of gear ratio.<\/p>\n

Gear Ratios<\/h3>\n

Inside the transmission are a series of variously sized, toothed gears that produce torque. Because the gears that interact with each other are different sizes, torque can be increased or decreased without changing the speed of the engine\u2019s rotational power all that much. This is thanks to gear ratios.<\/p>\n

Gear ratios represent the gears\u2019 relation to each other in size. When different sized gears mesh together, they can spin at different speeds and deliver different amounts of power.<\/p>\n

Let\u2019s look at a dumb-downed version of gears in action to explain this. Say you have an input gear with 10 teeth (by input gear, I mean a gear that is generating the power) connected to a larger output with 20 teeth (by output gear, I mean a gear that is receiving the power). To spin that 20-toothed gear once, the 10-toothed gear needs to turn twice because it\u2019s half as big as the 20-toothed gear. This means that even though the 10-toothed gear is spinning fast, the 20-toothed gear is turning slowly. And even though the 20-toothed gear is turning more slowly, it\u2019s delivering more force, or power, because it\u2019s larger. The ratio in this arrangement is 1:2. This is a low gear ratio.<\/p>\n

Or let\u2019s say the two gears connected to each other are the same size (10 teeth and 10 teeth). They\u2019d both spin at the same speed, and they\u2019d both deliver the same amount of power. The gear ratio here is 1:1. This is called a \u201cdirect drive\u201d ratio because the two gears are transferring the same amount of power.<\/p>\n

Or let\u2019s say the input gear was larger (20 teeth) and the output gear was smaller (10 teeth). To spin the 10-toothed gear once, the 20-toothed gear would only need to turn half way. This means that even though the 20-toothed input gear is spinning slowly and with more force, the 10-toothed output gear is spinning fast, and delivering less power. The gear ratio here is 2:1. This is called high gear ratio.<\/p>\n

Let\u2019s bring that concept back to the purpose of the transmission.<\/p>\n

Below you\u2019ll find a diagram of the power flow when the different gears in a 5-speed manual transmission vehicle are engaged.<\/p>\n

\"Gear<\/p>\n

First Gear.<\/strong> It\u2019s the largest gear in the transmission and enmeshed with a small gear. A typical gear ratio when a car is in first gear is 3.166:1. When first gear is engaged, low speed, but high power is delivered. This gear ratio is great for starting your car from a standstill.<\/p>\n

Second Gear.<\/strong> The second gear is slightly smaller than first gear, but still is enmeshed with a smaller gear. A typical gear ratio is 1.882:1. Speed is increased and power decreased slightly.<\/p>\n

Third Gear.<\/strong> Third gear is slightly smaller than the second, but still enmeshed with a smaller gear. A typical gear ratio is 1.296:1.<\/p>\n

Fourth Gear.<\/strong> Fourth gear is slightly smaller than the third. In many vehicles, by the time a car is in fourth gear, the output shaft is moving at the same speed as the input shaft. This arrangement is called \u201cdirect drive.\u201d A typical gear ratio is 0.972:1<\/p>\n

Fifth Gear.<\/strong> In vehicles with a fifth gear (also called \u201coverdrive\u201d), it is connected to a gear that\u2019s significantly larger. This allows the fifth gear to spin much faster than the gear that\u2019s delivering power. A typical gear ratio is 0.78:1.<\/p>\n

Parts of a Manual Transmission<\/h3>\n

\"Parts<\/p>\n

So by now, you should have a basic understanding of a transmission\u2019s purpose: it ensures that your engine spins at an optimal rate (neither too slow nor too fast) while simultaneously providing your wheels with the right amount of power they need to move and stop the car, no matter the situation you find yourself in.<\/p>\n

Let\u2019s take a look at the parts of a transmission that allow this to happen:<\/p>\n

Input shaft.<\/strong> The input shaft comes from the engine. This spins at the same speed and power of the engine.<\/p>\n

Countershaft.<\/strong> The countershaft (aka layshaft) sits just below the output shafts. The countershaft connects directly to the input shaft via a fixed speed gear. Whenever the input shaft spins, so does the countershaft, and at the same speed as the input shaft.<\/p>\n

In addition to the gear that takes power from the input shaft, the countershaft also has several gears on it, one for each of the car\u2019s “gears” (1st-5th), including reverse.<\/p>\n

Output shaft.<\/strong> The output shaft runs parallel above the countershaft. This is the shaft that delivers power to the rest of the drivetrain. The amount of power the output shaft delivers all depends on which gears are engaged on it. The output shaft has freely rotating gears that are mounted on it by ball bearings. The speed of the output shaft is determined by which of the five gears are in \u201cgear,\u201d or engaged.<\/p>\n

1st-5th gears.<\/strong> These are the gears that are mounted on the output shaft by bearings and determine which \u201cgear\u201d your car is in. Each of these gears is constantly enmeshed with one of the gears on the countershaft and are constantly spinning. This constantly enmeshed arrangement is what you see in synchronized transmissions or constant mesh transmissions, which most modern vehicles use. (We\u2019ll go into how all the gears can always be spinning while only one of them is actually delivering power to the drivetrain here in a bit.)<\/p>\n

First gear is the largest gear, and the gears get progressively smaller as you get to fifth gear. Remember, gear ratios. Because first gear is bigger than the countershaft gear it\u2019s connected to, it can spin slower than the input shaft (remember, the countershaft moves at the same speed as the input shaft), but deliver more power to the output shaft. As you move up in gears, the gear ratio decreases until you reach the point that the input and output shafts are moving at the same speed and delivering the same amount of power.<\/p>\n

Idler gear.<\/strong> The idler gear (sometimes called \u201creverse idler gear\u201d) sits between the reverse gear on the output shaft and a gear on the countershaft. The idler gear is what allows your car to go in reverse. The reverse gear is the only gear in a synchronized transmission that isn\u2019t always enmeshed or spinning with a countershaft gear. It only moves whenever you actually shift the vehicle into reverse.<\/p>\n

Synchronizer collars\/sleeves.<\/strong> Most modern vehicles have a synchronized transmission, meaning the gears that deliver power on the output shaft are constantly enmeshed with gears on the countershaft and are constantly spinning. But you might be thinking, \u201cHow can all five gears be constantly enmeshed and constantly spinning, but only one of those gears is actually delivering power to the output shaft?\u201d<\/p>\n

The other issue that comes up with the gears always spinning is that the drive gear is often rotating at a different speed than the output shaft that the gear is connected to. How do you sync up a gear spinning at a different rate as the output shaft, and in a smooth way that doesn\u2019t cause a lot of grinding?<\/p>\n

The answer to both questions: synchronizer collars.<\/p>\n

As mentioned above, gears 1-5 are mounted on the output shaft via ball bearings. This allows all of the gears to freely spin at the same time while the engine is running. To engage one of these gears, we need to firmly connect it to the output shaft, so power is delivered to the output shaft and then to the rest of the drivetrain.<\/p>\n

Between each of the gears are rings called synchronizer collars. On a five-speed transmission, there\u2019s a collar between the 1st and 2nd gears, between the 3rd and 4th gears, and between the 5th and reverse gear.<\/p>\n

Whenever you shift a car into a gear, the synchronizer collar shifts over to the moving gear you\u2019re looking to engage. On the outside of the gear are a series of cone-shaped teeth. The synchronizer collar has grooves to accept those teeth. Thanks to some excellent mechanical engineering, the synchronizer collar can connect to a gear with very little noise or friction even while the gear is moving, and sync the gear\u2019s speed with the input shaft. Once the synchronizer collar is enmeshed with the driving gear, that driving gear is delivering power to the output shaft.<\/p>\n

Whenever a car is \u201cneutral\u201d none of the synchronizer collars are enmeshed with a driving gear.<\/p>\n

Synchronizer collars are also something that\u2019s easier to understand visually. Here\u2019s a short little clip that does a great job explaining what\u2019s going on (starts at about 1:59 mark):<\/p>\n