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Manual transmission: device and principle of operation
Manual transmission: device and principle of operation

Currently almost every modern car is equipped with an automatic transmission, which is getting more complicated every time. And, despite the fact that these units are significantly superior to manual transmissions, the latter have their admirers. Some drivers still prefer vehicles with a mechanical (manual) transmission.

Manual Transmission

With an automatic transmission, everything is much more complicated, and if someone wants to understand the principle of operation of this unit, it is worth starting with a mechanical one. This article is dedicated to her.

The most necessary element of any car

Having heard the incomprehensible term "transmission" for the first time, many students immediately wonder what kind of unit it is and what it is for. Everyone knows that a car needs an engine to move. Almost every motorist is familiar with its principle of operation today:converting the reciprocating movements of the pistons into rotation of the crankshaft, otherwise referred to as torque.

However, this very rotation needs to be somehow transferred to the wheels. That's what the transmission is for. Those who are familiar with the peculiarities of driving cars with a manual transmission know this very well.

Under the term itself there are special mechanisms due to which the car moves at different speeds, if necessary, backs up (when the appropriate gear is engaged).

The design of these units is carried out by leading specialists at automobile factories. Moreover, important requirements are imposed on the transmission:

  • The node must be able to transmit maximum engine power.
  • Be reliable.
  • Driving should be easy.
  • The weight of all elements should be as light as possible.
  • Noise during operation is highly undesirable.

If the transmission is highly efficient and reliable, the driver should not worry about anything: the fuel will be used to the maximum, and the mechanism itself will faithfully serve for a long time.

But if the control of a manual transmission in a Nissan (for example) is difficult, this causes serious discomfort for the driver and significantly reduces his attentiveness on the road. All this threatens the risk of getting into an accident.

Machines with manual transmission

As for the weight, too heavy unit will be noticeably more expensive for buyers. ATtherefore, manufacturers are trying to lighten the weight of the mechanisms to the maximum.

What is meant by the amateur term "mechanics"?

Mechanical, or manual, as some drivers like to say, the gearbox (manual transmission) plays a simple, but at the same time important role. It not only transmits torque from the engine to the wheels, but also contributes to a change in the gear ratio. Moreover, it all depends on the driver himself - he decides when exactly it is necessary to switch for the correct performance of the entire car. This is the whole point of manual transmission control.

Despite the great popularity of the automatic transmission, the manual transmission is not going to give up, and here's why:

  • The design is as simple as possible.
  • Details and assemblies are reliable in terms of mechanical impact and overloads.
  • The cost of repair and maintenance of the unit (even capital) is not as high as that of its automatic competitor.

And while these qualities will be appreciated by motorists, some cars will continue to be equipped with "mechanics". After all, it is no coincidence that some modern automatic transmissions have a manual gearshift function. A vivid example of this is tiptronic.

Varieties of manual transmission

Mechanical boxes are classified according to the number of these steps:

  • 4;
  • 5;
  • 6.

The five-speed gearbox is the most common, which is why most cars are equipped with it. It also takes into accountnumber of shafts:

  • 3;
  • 2.

Three-shaft manual transmissions are predominantly used in rear-wheel drive vehicles, while two-shaft transmissions are found only in front-wheel drive vehicles. Actually, this is where the whole classification ends.

Gear ratio

Manual transmission refers to stepped mechanisms, that is, the amount of torque changes in steps. A step is usually called a pair of interacting gears. Each of these pairs transmits rotation to the wheels with a certain angular velocity. In other words, each stage has an individual gear ratio.

What is a transfer ratio?

Under the gear ratio should be understood as the ratio of the number of teeth of the driven gear to the number of teeth of the drive gear. In other words, the number of teeth for the driven gear is 60, and for the drive gear it is 30, that is, the gear ratio of this pair is 60: 30=2. For any gear, this parameter is the main one.

The lowest gear ratio is the largest, while the highest gear ratio is the smallest. Actually, due to this, a manual transmission can both increase and decrease torque.

The gear ratio affects such vehicle characteristics as acceleration dynamics and maximum speed. That is, the larger it is, the faster the crankshaft spins up to maximum speed, and the transmission itself is more “strong”. However, the speed that develops on it decreases. Therefore, with a large gearratio, you need to shift gears more often.

Manual transmission device

The engine of any car runs continuously, which is undesirable for the full and efficient operation of the gearbox. Shifting gears with the main shaft constantly rotating will inevitably lead to transmission failure due to tooth breakage and other negative consequences. For this reason, another node is needed - a clutch, with the help of which the power unit and transmission are separated for a while at the right time.

The principle of operation of the manual transmission

To understand how a manual transmission works, for novice drivers, we will analyze each of its types in more detail.

Three-shaft gearbox

The design of a three-shaft box includes three main elements - shafts:

  • Leading (primary) - connected to the clutch mechanism, for which it has special slots for its driven disk. The transmission of torque is carried out through a similar gear that is in rigid engagement with it.
  • Intermediate - located parallel to the first shaft. It also has a gear block in rigid engagement.
  • Driven (secondary) - located on the same axis as the drive shaft. It also has a block of gears, but, unlike other shafts, it is not fixed, and therefore can rotate freely. Between its gears there are synchronizers that are needed to synchronize the angular velocities of the gears of the driven shaft with the rotation of itself. With the car's manual transmission shaft, they are also rigidly fixed,but can move in the longitudinal plane by means of a spline connection. All modern units have synchronizers in every gear.

Besides this, there is also the switching mechanism itself, and all this is located in the crankcase of the unit, called the housing. As for the first, it is located directly on the gearbox housing. The mechanism is presented as a control lever and sliders with forks. There is also a locking device to prevent two gears from being engaged at the same time.

For the manufacture of the crankcase itself, the box uses aluminum or magnesium alloy. In addition to all the necessary parts and mechanisms, it stores oil.

Twin-shaft gearbox

This box is arranged almost the same, but with a small addition. It also contains two shafts:

  • host;
  • slave.

Both have a set of gears with synchronizers, and they are arranged in parallel, as in the design described above. And the mentioned addition is the presence of the main gear and differential in the crankcase of a mechanical gearbox. Their function is to transmit torque to the driving wheels of the car. Moreover, the differential, if necessary, can provide different angular speeds.

Manual transmission removed from car

Of course, it does not do without a switching mechanism, which is usually remote. In other words, it is located outside the box body. And for their connection, traction or cables are used. Moreover, the cable connection is optimal, and therefore more oftenapplies.

The principle of operation of the checkpoint

When the control lever is in the neutral position, no torque is transmitted from the crankshaft to the wheels. When the engine starts, the input shaft rotates with the crankshaft. To engage the desired speed, be sure to press the clutch pedal to disengage the shafts.

Now you can move the control lever in the desired direction. In this case, the synchronizer clutch is moved by means of a fork and the required pair of gears is activated. This allows you to choose the optimal torque depending on road conditions.

Driving a car with a manual transmission will be discussed later, but for now the principle of operation of a different design.

How a two-shaft gearbox works

Two-shaft gearboxes work on almost the same principle, but there is still a difference: torque is transmitted using only a pair of gears, while in a three-shaft design, the third gear of the countershaft takes part. In addition, there is no direct transmission, and the gear ratio is 1: 1.

Besides, it is not the fork, but the stock, that makes the switching of the stages. It is he who pushes the necessary gear, and it engages with the other, and then it is fixed. To turn on the reverse gear, a separate gear is activated on its shaft. And this is true for both types of manual transmissions.

Manual Benefits

Some positive points have already been listed above, so let's make a kind of generalization. Characteristic advantages of the box:

  • relativelylight weight;
  • low cost;
  • design is simple and clear;
  • high reliability;
  • maintenance and repairs are inexpensive.

For machines with a manual transmission, the engine is rigidly connected to the transmission, thereby achieving maximum efficiency when traveling on ice or off-road. In addition, the manual transmission can, if necessary, completely disconnect from the engine for unhindered towing or pushing.

Flaws are also present

Unfortunately, you cannot do without minuses, although there are not so many of them. First of all, this concerns the need for constant periodic gear changes, which can tire the driver on long trips.

Driving a car with a manual transmission

Other disadvantages include:

  • The gear ratio changes in steps.
  • Clutch life is not high enough.

Therefore, although the "mechanics" is the main type of transmission, it is far from the most popular. Perhaps in a couple of decades it will completely lose its relevance, and finally.

Peculiarities of driving with a manual transmission

For the proper operation of vehicles with manual transmission, certain skills and abilities are required. Many beginners, especially women (maybe not all), can have difficulty. It is necessary to remember the position of the control lever for each gear. It's not difficult, since it has a diagram on it. In addition, you should know in what speed rangeevery transmission works.

Speed ​​modes depending on transmission:

  • 1st gear - 15-20 km/h.
  • 2nd gear - 30-40 km/h.
  • 3rd gear - 50-60 km/h.
  • 4th gear - no more than 80 km/h.
  • 5th gear - over 80 km/h.

But it is better to focus on the readings of the tachometer. It is recommended to shift to a higher gear before reaching a certain number of revolutions of the crankshaft, depending on the type of engine:

  • for diesel - 1500-2000;
  • for gasoline - 2000-2500.

To avoid premature repair of a manual transmission, make sure the lever is in neutral before starting the engine. The left foot controls only the clutch pedal, and the right foot is responsible for the other two - this is the only way you can not confuse anything.

Before starting off, the clutch is depressed, the first gear is engaged, then the clutch is smoothly released with the left foot, while the accelerator pedal is also smoothly pressed with the right foot. Further, the switching is carried out upon reaching the speed threshold: the clutch pedal is depressed (the foot must be removed from the gas), the second gear is engaged - then everything is the same.

The main malfunctions of the "mechanics"

Despite its simplicity, manual transmission is a rather complex system with a large number of moving parts. Because of this, it can have a variety of malfunctions, but often it is a failure of the main components of the unit, a lack of oil in the crankcase, or a weakeningfixing the elements of the box.

Manual transmission repair

This can happen due to improper operation, poor quality of parts, their natural wear and tear. In addition, this can also include poor-quality repairs or a complete lack of maintenance.

You can determine whether a manual transmission needs to be replaced or repaired by its characteristic features. If it makes noise when the lever is in neutral, it means that the drive shaft bearing has worn out. It could also be due to a lack of oil. And if noise occurs during gear shifting, then the problem may lie in the synchronizer clutches.


Knowing the device and the principle of operation of a mechanical box, it will be a little easier to understand how an automatic transmission works. The manual transmission was and still remains a practical and familiar unit for many drivers, despite some nuances. In general, you need to know your car inside and out, which will enrich you with invaluable experience.

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