Manual Transmission Parts and Function

What is Manual Transmission?

A manual transmission is a gearbox that allows the driver to select from various gear ratios when driving the car. Lower gear ratios provide more torque but slower speeds, whereas higher gear ratios provide less torque but faster speeds. Because different gear ratios are referred to as “speeds,” a “six-speed” manual transmission has six forward gear ratios.

The manual transmission comprises three shafts with constantly-intermeshed gears of various sizes, and the clutch connects the engine’s input shaft to the output shaft. The countershaft contains many gears and is constantly meshed with the input shaft.

The output shaft connects the countershaft to the driveshaft, connecting the wheels. The output shaft links to the transfer case first in four-wheel and all-wheel drive vehicles. Reverse gear is fitted on a fourth shaft to shift direction.

Fig1: Manual Transmission
Source: How Stuff Works

The gears themselves are freewheeling and are not attached to the output shaft. On the other hand, locking collars spin with the output shaft and can shift or slide back and forth to engage one of the gears. It’s for this reason that we term it “shifting” gears.

The input shaft and countershaft are rotating, as are the output shaft gears, in “neutral,” with no gear chosen and the clutch released, but the output shaft does not move since none of the locking collars are engaged. The countershaft connects to the driveshaft and then to the wheels.

How Does A Manual Transmission Work?

For example, the driver depresses the clutch and disengages the input shaft to shift gear when engaging first gear. The driver enters first gear with the gearshift lever, and the linkage advances the gearshift fork from first to second gear. The locking collar must be connected to the first gear and locked to the output shaft.

Because 1st gear is connected to the output shaft by the locking collar, the output shaft turns if the clutch is released and the input shaft engages. If the driver accelerates, the process is repeated when shifting to second gear, but the gearshift lever is shifted to second gear.

The input shaft is re-engaged when the clutch is released, and power is transmitted through 2nd gear this time. A second shift linkage, a shift fork, and a locking collar are utilized between 3rd and 4th gear while shifting into 3rd gear. Because the countershaft and output shaft move at different rates, shifting from first to second gear is difficult.

Attempting to change into a higher gear when the car slows down is equivalent to turning the shaft at two different speeds, which is impossible. Synchronizer rings work like small clutches, using friction to bring the circlip and gear up to speed. They will readily interlock at this point.

Components of Manual Transmission & Their Functions:

Different components form the manual transmission mechanism. Each of them is crucial for the gearing shifting and clutch releasing abilities. You won’t drive smoothly if one of these components fails.

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1. Clutch Disc:

A metal disc with a frictional facing, similar to brake shoes or pads, makes up the clutch disc. The lining is made of a non-organic woven or molded material with soft metal particles such as aluminum or brass. It increases the lining’s strength, and a set of radial grooves on the lining’s face improves the flywheel’s grip on the disc.

Fig2: Clutch Disc

The transmission’s input shaft mates with a splined hub in the disc’s center, allowing direct mechanical interaction. The transmission’s input shaft connects to a splined hub in the disc’s center. Driveline shock and vibration are dampened by torsional springs placed between the clutch hub and the lining.

The clutch disc transfers engine torque directly to the transmission’s input shaft. When combined with the pressure plate and flywheel, the clutch disc controls power from the engine to the transmission.

2. Clutch Pedal:

The clutch pedal is used to disconnect the drive from the engine to the transmission. The pedal converts a parabolic clutch pedal swing into a linear movement. This linear movement is transferred to thrust bearing movement by mechanical linkages, cable, or hydraulic fluid displacement.

Fig3: Clutch Pedal

The friction clutch, located between the engine’s flywheel and the input shaft, is activated when you step on the clutch pedal. The clutch’s job is to separate the engine from the transmission. The engine and transmission continue to spin when the pedal is pushed, but they. With no torque transfer from the engine to the gearbox, making it is possible for you to shift gears.

3. Flywheel:

Fig4: Flywheel

The clutch disc obtains torque via the flywheel, a circular component. Functions of the flywheel are – i) to keep a rotational mass (inertia) to help the engine rotate and provide torque more consistently while running. ii) to install a ring gear on which the starter motor can engage iii) to offer one of the friction disc’s driving friction surfaces.

4. Synchronizers:

Synchronizers, or synchros, are used in modern passenger cars to eliminate the necessity for double-clutching. The synchronizers induce engagement between the collar and the gear, allowing for synchronization of their speeds. You’ll need the synchronizers to prevent this because the speeds may differ at times.

Fig5: Synchronizer

The speed of the shaft is adjusted by a synchronizer so that the gears align more quickly as you shift—the slider presses against the synchronizer’s keys or balls, subsequently pressing against the blocker ring.

The ring then pushes against the gear’s cone, causing friction that helps to equalize shaft speeds. A synchronizer’s function is to allow meshing gears to be changed while the vehicle is driving without compromising the mechanical integrity of the gears or causing interior noise.

5. Gears:

The transmission has a variety of gear sizes. Big gears have a lot of teeth, while small gears have fewer teeth. Smaller gears produce less torque, allowing the vehicle to accelerate. The amount of power available from the engine is determined by the gears.

Fig6: Gears

The first gear has the highest pulling power but the least speed possibilities, whereas the fifth gear has the least pulling strength but the widest speed range.

6. Selector Fork:

The gear selector fork includes a body forming a pair of support plates with respective coaxial through-holes for supporting the fork slidably along a stationary rod of the gearbox. A pair of prongs fixed to the body and forming respective actuating portions can operate a sliding coupling sleeve of the gearbox at their distal ends.

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An actuating nose is fixed to the body to impart the sliding movement along the stationary rod to the fork. The body and prongs are shaped so that two forks with similar bodies and prongs can be mounted on the same stationary rod and in the direction of sliding along the stationary rod, at least partially overlapped.

7. Stick Shift:

It is the part that you can handle with your hand. It’s the central console’s vertical stick that protrudes. It is attached to the gearbox and can be used to change gears. A car with a manual or standard transmission is sometimes referred to as a stick shift.

The vehicle’s stick shift allows drivers to change ratios to accelerate the vehicle manually. The transmission is connected to the stick shift and placed in the car’s center.

8. Collar:

The collar secures the gear selection and permits torque to pass to the output shaft when you pick it up.

Which Component Inside the Manual Transmission Wears the Most?

The manual transmission’s main wear components are the clutch and release bearing. The clutch is attached to the engine’s flywheel at the back. A “pressure plate” applies pressure to the clutch disc to keep it securely on the flywheel when the clutch is engaged.

It permits the torque from the engine to be transmitted directly to the transmission and drive train. The release bearing is pushed against the spring fingers on the pressure plate when the clutch pedal is depressed to disengage, causing the clutch to release.

Types of Manual Transmission:

1. Sliding Mesh Gearbox:

The Sliding Mesh Gearbox was the first automotive gearbox or transmission system. The world’s largest-ever transmission system with 3-speed sliding mesh transmission was designed by French Inventors Louis-Rene and Emile Levassor in 1894.

The desired gear ratio is obtained by sliding the required gears and the appropriate matching gears. A sliding mesh gearbox is a transmission system of several sets of gears and shafts arranged logically.

Fig7: Sliding Mesh Gearbox

The shifting or meshing of different gear ratios is accomplished by moving gears to the right and left across the splined shaft with the help of a gear lever actuated by the driver. The gears on the layshaft are securely fixed to the shaft, but the gears on the main shaft can glide on it via splines but are otherwise in permanent rotational mesh with the shaft.

2. Constant Mesh Gearbox:

A constant mesh gearbox is used to keep an automobile running smoothly. It increases the spinning force (Torque) while lowering the speed. It. In the nineteenth century, the first manual gear system was invented.

Fig8: Constant Mesh Gearbox

Several gear ratios are available, each producing a different torque and speed ratio. Additionally, the reverse mechanism is present. All of the gears mesh at any given time in the manual transmissions that have lately been designed.

A dog clutch is used to shift gears and calculate gear ratios in the constant-mesh gearbox. A clutch shaft, layshaft, countershaft, and output or main shaft make up the constant mesh gear.

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All gears on the main shaft and countershaft are connected in this system. A mechanism called a dog clutch is utilized to achieve the gear ratio. The gear is attached to the dog clutch for the desired speed and gear ratio.

3. Synchromesh Gearbox:

It’s a manually driven transmission that switches gears between gears already spinning at the same speed. The gears in this gearbox can revolve freely or be locked on the layout shaft. The synchronizer is the most important component of this gearbox since it regulates the speed.

Fig9: Synchromesh Gearbox

A synchronizer is a clutch that allows parts to rotate at different rates. Cone friction is utilized to synchronize the speeds. The Synchro cone and balk ring are the two parts of this synchronizer.

The ring is a part of the synchronizer, while the cone is a portion of the gear. The balk ring stops the gears from engaging until they have reached the proper rotational speeds.

Difference between Synchromesh Gearbox and Constant Mesh gearbox

  • Synchronizers are used in synchromesh gearboxes to engage and disengage gears. On the other hand, dog clutches are used to engage and disengage gears.
  • In the case of the synchromesh gearbox, there will be no slippage. While in slip, the constant mesh gearbox is used.
  • The synchromesh gearbox provided complete locking action. The continuous mesh gearbox partially satisfied the locking action.

Advantages of Manual Transmission

  • A manual transmission can easily fit into your budget because it has fewer moving parts, making it less expensive to buy.
  • You can shift your automobile into neutral when going down a slope. That means less power is sent to the engine, and less gasoline is burned. As a result, higher gas mileage is possible.
  • Manual transmissions have fewer moving parts, and repair costs are substantially lower since they have fewer parts.
  • Because they are less sophisticated than automatics and have fewer moving parts, they are easier to maintain.
  • If you have a manual transmission vehicle, you’ll shift into fourth or fifth gear as soon as feasible and travel at higher speeds.
  • Engine oil wears out less quickly and does not require regular replacement.

Disadvantages of Manual Transmission

  • Due to the increasing use of automatic transmissions, manual transmissions are rarely available.
  • When driving a car with a manual transmission, the clutch will eventually wear out, necessitating a costly replacement.
  • It might be tough to learn to drive a vehicle with a manual transmission.
  • If you are not prepared, driving uphill can be dangerous and tough.
  • Frequent stopping, starting, and changing gears manually in heavy traffic can make driving difficult.


A manual transmission is the traditional type of transmission still used in automobiles. It employs a foot-operated driver-operated clutch for engagement and disengagement. It can also be done using a hand lever and a hand-operated gear selector. It controls the flow of torque from the engine to the transmission.

In short, manual transmission vehicles are both cheaper and more complex. Selecting a transmission system is a difficult task. If performance and driving pleasure is important to you, a manual transmission may be the best option.

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