Most cars only have automatic transmissions. Manual transmission is a type of engine where the driver pushes pedals and gears to change how fast or in what direction a vehicle moves. It has been around for centuries, and still remains an important part of car history today by being the default option on classic vehicles that were made before automatic was developed.

In order to drive a manual transmission, you need to learn how to shift gears. The shifter is on the steering wheel and it has three pedals, one for gas and two for the brake. You use your right foot to press down on the gas pedal while pressing down on the clutch with your left foot. Then you use your left foot to press down on the brake pedal while pressing up on the clutch with your right foot. Read more in detail here: how to drive a manual transmission.

Welcome back to Gearhead 101, a series aimed at educating automotive newbies on the fundamentals of vehicle operation.

You know how to drive a stick shift because you read The Art of Manliness. But, when you swap gears, do you realize what’s going on behind the hood?

No?

It’s your fortunate day today!

We look at the ins and outs of how a manual gearbox works in this episode of Gearhead 101. By the end of this article, you should have a rudimentary grasp of this important component of your vehicle’s powertrain.

Let’s get started by rolling up our sleeves.

Note: Before reading about how a gearbox works, I strongly advise you to examine our Gearhead 101s on engines and drivetrains.

What Do Transmissions Actually Do?

Let’s talk about what transmissions do in general before we get into the intricacies of how a manual gearbox works.

The engine in your automobile generates rotational power, as we described in our primer on how a car engine works. We must transmit the rotational power to the wheels in order to propel the automobile. That’s what the car’s drivetrain, which includes the gearbox, does.

However, there are a few issues with the power generated by an internal combustion engine. To begin with, it only produces useful power, or torque, within a certain range of engine speed (known as an engine’s power band). If you drive too slowly or too quickly, you won’t have enough torque to get the vehicle going. Second, automobiles often need more or less torque than the engine’s power range can give.

To comprehend the second difficulty, you must first comprehend the first. To comprehend the first issue, you must first comprehend the distinction between engine speed and engine torque.

The pace at which the engine’s crankshaft rotates is known as engine speed. This is expressed as a number of rotations per minute (RPMs).

The amount of twisting force generated by an engine at its shaft at a given rotational speed is referred to as engine torque.

To illustrate the difference between engine speed and engine torque, a vehicle technician provided this helpful analogy:

Assume you’re an engine attempting to hammer a nail into a wall:

In a minute, how many times do you strike the nail head?

Torque is the force with which you strike the nail every time.

Consider the last time you hammered some nails. You probably observed that you weren’t hitting the nail with much power if you were hammering extremely rapidly. Furthermore, you were undoubtedly fatigued from all of the frenzied swinging.

In contrast, if you took your time between swings but made sure that each one was as hard as possible, you’d be able to drive the nail in with fewer strokes but it would take a little longer since you weren’t swinging at a consistent cadence.

 

In an ideal world, you’d discover a hammering speed that enabled you to pound the nail head multiple times with a fair amount of power without becoming exhausted. It’s just perfect, not too quick, not too sluggish.

So, we’d want our car’s engine to do the same. We want it to spin at a speed that will enable it to generate the required torque without overworking itself. The engine must remain within its power band.

You won’t have enough torque to drive the automobile ahead if the engine is spinning below its power range. When it exceeds its power band, torque begins to decline, and your engine begins to sound as if it is going to break due to stress (similar to what occurs when you attempt to hammer too hard — you strike the nail with less power and get very exhausted). If you’ve ever revved your engine till the tachometer reads red, you know what I’m talking about. Your engine sounds like it’s going to die, yet you’re not getting any closer to your destination.

So you know how important it is to maintain a car in its power band in order for it to function properly.

But this gets us to our second issue: in some conditions, automobiles need more or less torque.

When starting an automobile from a stop, for example, a lot of power, or torque, is required to get the vehicle moving. If you press down hard on the gas pedal, the engine’s crankshaft will spin very rapidly, causing the engine to exceed its power range and potentially destroying itself. The worst part is that you won’t even be able to move the automobile since an engine’s torque decreases as it moves outside its power range. We need a lot more torque in this case, but we’ll have to sacrifice some speed to obtain it.

What if you simply push a little harder on the gas pedal? That’s probably not going to start the engine spinning fast enough to go into its power band and generate the torque needed to get the vehicle moving in the first place.

Let’s look at a different scenario: Let’s imagine you’re going down the interstate and the automobile is traveling quite quickly. Because the automobile is already going quickly, you don’t need to deliver as much power from the engine to the wheels. A lot of the work is being done by sheer momentum. As a result, you may run the engine at a greater RPM without having to worry about the quantity of power transferred to the wheels. We need greater rotational speed and less rotational power flowing to the wheels.

What we need is a technique to increase the engine’s power when it’s required (starting from a stop, climbing a hill, etc.) while reducing the amount of power transmitted when it’s not (going downhill or going really fast).

 

This is where the transmission begins.

No matter what condition you’re in, the gearbox guarantees that your engine spins at an ideal pace (neither too slow nor too fast) while simultaneously giving the proper amount of power to your wheels to drive and stop the automobile. It is able to achieve this by using the power of gear ratio to convey power effectively across a succession of various sized gears.

Aspect Ratios

A set of toothed gears of varying sizes provide torque within the gearbox. Torque may be raised or lowered without increasing the engine’s rotational power substantially since the gears that engage with each other have different sizes. Gear ratios are to thank for this.

The size relationship between gears is represented by gear ratios. Various sized gears may spin at varying speeds and provide different amounts of power when they mesh together.

To further understand this, consider a dumbed-down rendition of gears in motion. Assume you have a 10 tooth input gear (by input gear, I mean a gear that generates the power) coupled to a bigger 20 tooth output gear (by output gear, I mean a gear that is receiving the power). Because the 10-toothed gear is half the size of the 20-toothed gear, it must revolve twice to spin the 20-toothed gear once. This implies that while the 10-toothed gear rotates quickly, the 20-toothed gear rotates slowly. Because the 20-toothed gear is bigger, it delivers greater force, or power, despite its slower rotation. This pattern has a 1:2 ratio. This is a very low gear ratio.

Let’s imagine the two gears that are linked are the same size (10 teeth and 10 teeth). They’d both spin at the same speed and provide the same amount of energy. Here, the gear ratio is 1:1. Because the two gears transmit the same amount of power, this is referred to as a “direct drive” ratio.

Consider the case when the input gear is bigger (20 teeth) and the output gear is smaller (10 teeth). The 20-toothed gear would only have to turn half way to spin the 10-toothed gear once. This implies that although the 20-toothed input gear rotates slowly and with higher force, the 10-toothed output gear rotates quickly and delivers less power. The gear ratio is 2:1 in this case. This is referred to as a high gear ratio.

Let’s bring that notion back to the transmission’s goal.

A schematic of power flow while the various gears of a 5-speed manual gearbox car are engaged may be found below.

Gear ratio in a manual transmission illustration diagram.

This is the first gear. It’s the transmission’s biggest gear, and it’s intertwined with a smaller gear. When an automobile is in first gear, the normal gear ratio is 3.166:1. When you shift into first gear, you get a modest speed yet a lot of power. This gear ratio is ideal for getting your automobile started from a stop.

Second Gear, to be precise. The second gear is somewhat smaller than the first, although it is still mated to a smaller gear. 1.882:1 is a common gear ratio. The speed has risen somewhat but the power has diminished little.

 

It’s in third gear. The third gear is somewhat smaller than the second, yet it is still intertwined with another smaller gear. The common gear ratio is 1.296:1.

This is the fourth gear. The fourth gear is a fraction of a size smaller than the third. By the time an automobile reaches fourth gear, the output shaft is travelling at the same speed as the input shaft in many cars. “Direct drive” is the term for this setup. 0.972:1 is a common gear ratio.

Fifth gear is a term used to describe a vehicle that It is coupled to a much bigger gear in cars having a fifth gear (also known as “overdrive”). This permits the fifth gear to rotate at a considerably quicker rate than the power transmission gear. 0.78:1 is a common gear ratio.

A Manual Transmission’s Components

Parts of a manual transmission illustration diagram.

So, by now, you should have a basic grasp of what a gearbox does: it guarantees that your engine spins at an appropriate pace (neither too slow nor too fast) while also giving the proper amount of power to your wheels to drive and stop the automobile, regardless of the scenario.

Let’s look at the components of a transmission that make this possible:

Shaft for the input. The engine provides the input shaft. This rotates at the same rate and with the same power as the engine.

Countershaft. The countershaft (also known as the layshaft) is located underneath the output shafts. A fixed speed gear links the countershaft to the input shaft directly. The countershaft spins at the same speed as the input shaft whenever the input shaft rotates.

The countershaft has many gears on it, one for each of the car’s “gears” (1st-5th), including reverse, in addition to the gear that draws power from the input shaft.

Shaft for the output. Above the countershaft, the output shaft runs parallel. The shaft that transmits power to the remainder of the drivetrain is this one. The quantity of power delivered by the output shaft is determined by which gears are engaged on it. Ball bearings are used to place freely moving gears on the output shaft. Which of the five gears is in “gear,” or engaged, determines the output shaft’s speed.

1st through 5th gears These are the gears that are supported by bearings on the output shaft and decide the “gear” your vehicle is in. Every one of these gears is continually entangled with one of the countershaft’s gears and rotating. Most current automobiles employ synchronized transmissions or continuous mesh transmissions, which have this continually entangled configuration. (In a moment, we’ll explain how all the gears might be turning while only one of them is really giving power to the drivetrain.)

The first gear is the biggest, and the gears grow smaller as you approach closer to fifth gear. Keep in mind the gear ratios. Because the first gear is larger than the countershaft gear to which it is linked, it may spin slower than the input shaft (remember, the countershaft travels at the same speed as the input shaft) while still delivering more power to the output shaft. The gear ratio reduces as you go through the gears, until the input and output shafts are moving at the same speed and producing the same amount of power.

 

Gear for idlers. The idler gear (sometimes known as the “reverse idler gear”) is located between the output shaft’s reverse gear and a countershaft gear. Your car’s idler gear is what permits it to reverse. In a synchronized transmission, the reverse gear is the only one that isn’t constantly entangled or rotating with a countershaft gear. It only moves when the car is really shifted into reverse.

Collars and sleeves with synchronizers. Most contemporary automobiles have a synchronized gearbox, which means the gears on the output shaft that produce power are continually entangled with gears on the countershaft and rotating. “How can all five gears be continually entangled and spinning, yet only one of those gears is really supplying power to the output shaft?” you may wonder.

Another difficulty with the gears constantly spinning is that the driving gear often rotates at a different speed than the output shaft to which the gear is linked. How do you synchronize a gear that spins at a different pace than the output shaft in a smooth, non-grinding manner?

Synchronizer collars are the solution to both questions.

As previously stated, ball bearings are used to install gears 1-5 on the output shaft. While the engine is operating, this permits all of the gears to freely rotate at the same time. We must securely link one of these gears to the output shaft in order for power to be supplied to the output shaft and subsequently to the remainder of the drivetrain.

Synchronizer collars are rings that sit between each gear. A collar separates the first and second gears, the third and fourth gears, and the fifth and reverse gears on a five-speed gearbox.

The synchronizer collar switches over to the moving gear you’re attempting to engage whenever you shift an automobile into a gear. A set of cone-shaped teeth run around the exterior of the gear. The teeth are accepted by grooves in the synchronizer collar. The synchronizer collar can attach to a gear with very little noise or friction, even when the gear is moving, and sync the gear’s speed with the input shaft, thanks to some good mechanical engineering. The driving gear is giving power to the output shaft after the synchronizer collar has entangled with it.

None of the synchronizer collars are entangled with a driving gear while the automobile is in “neutral.”

Collars with synchronizers are also easy to comprehend visually. Here’s a brief video that does a good job of describing what’s going on (it begins at the 1:59 mark):

 

Gearshift. To shift an automobile into gear, you move the gearshift.

Shift rod is a kind of shifter. The synchronizer collars are moved towards the gear you wish to engage by the shift rods. There are three shift rods on most five-speed autos. The gearshift is attached to one end of a shift rod. A shift fork holds the synchronizer collar at the opposite end of the shift rod.

 

Toss the fork in a different direction. The synchronizer collar is held in place by the shift fork.

Clutch. The clutch is located between the transmission’s engine and gearbox. When the clutch is disengaged, power flow between the engine and the transmission gearbox is interrupted. The engine may continue to operate even if the rest of the car’s powertrain isn’t receiving any power because of this power disconnect. Shifting gears is considerably simpler and avoids damage to the transmission gears when the engine power is disengaged from the gearbox. This is why, everytime you transfer gears, you release the clutch by pressing the clutch pedal.

When you release your foot from the clutch pedal, power to the engine and gearbox is restored.

Manual Transmissions and How They Work

So, let’s tie everything together and go through what occurs when you swap gears in a car. To begin, we’ll start an automobile and move into second gear.

Before turning the key on a manual gearbox automobile, you release the clutch by pushing down on the clutch pedal. This interrupts the passage of power from the engine’s input shaft to the gearbox. This enables your engine to function without supplying electricity to the rest of the car.

You shift the gearshift into first gear with the clutch disengaged. The shifting fork, which is attached to the output shaft through ball bearings, is moved towards first gear by a shifting rod in your transmission’s gearbox.

The first gear on the output shaft is entangled with a countershaft-connected gear. The countershaft rotates at the same speed as the engine’s input shaft and is connected to it through a gear.

A synchronizer collar is attached to the shifting fork. The synchronizer collar has two purposes: 1) it secures the driving gear to the output shaft so that it can transmit power to it, and 2) it guarantees that the gear is in sync with the output shaft’s speed.

The gear is securely attached to the output shaft after the synchronizer collar is entangled with the first gear, and the vehicle is now in gear.

To start the automobile rolling, gently push down on the gas pedal (which increases engine power) while gradually releasing your foot from the clutch (which engages the clutch and reconnects power between the engine and transmission gearbox).

The output shaft spins slower than the engine’s input shaft because the first gear is huge, but it delivers more power to the remainder of the drivetrain. Thanks to the miracles of gear ratios, this is possible.

If you’ve followed the instructions properly, the automobile will begin to move ahead gently.

You’ll want to go faster after you’ve started the automobile. However, you won’t be able to move very quickly in first gear since the gear ratio forces the output shaft to rotate at a specific pace. If you floor the gas pedal when the automobile is in first gear, the engine’s input shaft will spin very rapidly (potentially damaging the motor), but you won’t notice any gain in vehicle speed.

 

To boost the output shaft’s speed, we must move to second gear. So we change into second gear and step on the clutch to withdraw power from the engine and the gearbox. This shifts the shifting rod, which is equipped with a shift fork and synchronizer collar, into second gear. The synchronizer collar aligns the speed of the second gear with the output shaft and secures it in place. The output shaft may now spin faster without causing the engine’s input shaft to spin faster in order to create the necessary power.

Rinse, wash, and repeat for the remaining five gears.

The only exception is reverse gear. Unlike the other driving gears, where you may shift up without coming to a full stop, shifting in reverse requires you to come to a complete stop. This is due to the fact that the reverse gear isn’t always entangled with a counter shaft gear. Make sure the countershaft is not moving before sliding the reverse gear into its matching countershaft gear. You must have the automobile totally stopped to verify the countershaft is not rotating.

Sure, you can put a forward-moving automobile into reverse gear, but it won’t sound or feel good, and you risk causing serious transmission damage.

You’ll know what’s going on under the hood now everytime you push your automobile into gear. Then there are automatic transmissions.

 

 

Watch This Video-

The “manual transmission components” are the parts of a vehicle that is used to shift gears. These components include the clutch, gearbox, and differential. The clutch is located in the engine compartment and it’s connected to the flywheel. The gearbox is found between the engine and the differential and it contains several gears that allow for different speeds. The differential is located on both axles of a vehicle and it helps with turning or spinning by allowing one wheel to turn at a time.

Frequently Asked Questions

Why is a manual transmission used in a motor vehicle?

A: Manual transmissions are mostly used in older cars, due to their simplicity and use of hand gears.

What keeps a manual transmission in gear?

A: The transmission in your car is a manual transmission. It uses a clutch to keep the gears engaged and it works by using the flywheel of an engine which spins against a connected gearbox, causing friction that keeps its teeth turning as you move forward.

Related Tags

  • 5-speed manual transmission diagram
  • what is manual transmission
  • types of manual transmission
  • how automatic transmission works
  • manual transmission diagram clutch
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