The structure of a manual transmission and how it works

Manual transmission - time-tested reliability

Almost any modern car (except electric cars) is necessarily equipped with a gearbox. The most popular types of gearboxes are:

Manual Transmission;
Automatic transmission;
Variable speed drive;
Robotic gearbox.

Purpose and design of a manual gearbox

A manual gearbox is needed in a car to change the gear ratio from the engine to the wheels. Gear shifting occurs due to the driver’s muscular strength, his mechanical efforts in relation to the manual transmission.

That is why such a gearbox is called a manual gearbox. The driver himself controls when to shift the manual transmission selector to a higher or lower gear. Modern manual transmissions come in 5, 6 and even 7 speeds.

Most often in modern cars a 6-speed gearbox is used.

Operating principle of a manual transmission

The mechanical gearbox includes:

The box itself, which is a multi-stage gearbox;
Clutch;
Various shafts and gears.

If we explain the principle of operation of a manual transmission for dummies, then we can form it like this:

Gears change the speed of rotation between the shafts. By changing the size of the gears, switching to an up or down gear occurs;
Without a clutch, changing gears on the move is impossible. Its job is to separate the engine and transmission. This procedure helps you change gears without breaking the gears and shaft.

Each manual transmission (if it is not an innovative model) has a similar design. Toothed gears are located on the shafts (on their axes). Manual transmissions come with two or three shafts, and the housing is called a crankcase.

Three-shaft system design

The three-shaft system is equipped with three shafts:

Drive shaft;
Intermediate shaft;
Driven shaft.

The driven shaft of a manual transmission is connected to the drive shaft using a bearing inside the first shaft and is positioned in such a way that the driven and drive axes are related to each other. In turn, this structure allows them to rotate independently of each other.

The gears of the driven axle are not rigidly fixed in relation to the driven shaft, and the gears themselves have special delimiters - a synchronizer-clutch. Such delimiters, unlike gear blocks, are firmly attached to the driven shaft.

However, this does not prevent them from moving along the Spitz along the axis.

The ends of the synchronizer clutch are shaped like toothed rims, which allows them to come into contact with the rims at the ends of the driven shaft gears. Currently, the gear unit is equipped with such synchronizers in all forward gears.

With a rear-wheel drive car, the transmission of torque and speed to the drive wheels occurs through the driveshaft, and with a front-wheel drive car, with the help of CV joints and a gearbox.

If there is no gear and the clutch directly engages the driven and drive shafts, the gearbox provides the highest possible efficiency.

For reverse gear, the gearbox device is equipped with a gear that allows you to change the direction of rotation in the reverse order.

Recently, manufacturers of manual transmissions have given preference to helical gears.

Unlike spur gears, such gears produce minimal noise during operation and are more wear-resistant.

The shelf life of such gears is determined by the material from which they are made: high-alloy steel, hardened by high-frequency current and normalized to relieve stress.

Double-shaft box device

The operation of a manual transmission equipped with a two-shaft gearbox follows the same principle as a three-shaft gearbox. The only difference is the gear arrangement. Instead of one on the drive axle, there is a whole block of gears. The intermediate shaft is missing, but the two remaining shafts run parallel to each other.

What is the synchronizer used for in a manual transmission?

Most passenger cars, both domestic and foreign, have manual transmissions that have a synchronizer. This element helps to equalize the speed of the gears, which leads to lower noise levels and easier gear shifting, which cannot be achieved if the gearbox does not have a synchronizer.

How does the gear shift process occur?

It doesn’t matter what kind of drive your car has, front or rear, a special lever is always responsible for the gear shifting process. If you look at a cross-section of a manual transmission, you will notice that the location of the lever on front-wheel drive is significantly different from its location on rear-wheel drive.

Cars with rear-wheel drive have a simpler gearshift lever layout, which simplifies their repair and maintenance. The lever is located directly on the gearbox housing, the shift mechanism is hidden inside the housing. This location has many advantages, but, unfortunately, it is not without its disadvantages.

Design advantages:

A very simple solution, which greatly simplifies the DIY repair process;
Gear shifting occurs very clearly;
Due to the absence of “extra” components, this design is very durable.

Design disadvantages:

This system cannot be installed on front-wheel drive vehicles;
If a car with rear-wheel drive has an engine located at the rear, then this also makes it impossible to use this design (there are very few such cars).

On front-wheel drive vehicles, the gearshift lever may be located in the following locations:

On the floor, in the space between the front seats;
Directly on the steering column;
Near the instrument panel.

This feature leads to the fact that the multi-stage manual transmission on front-wheel drive vehicles operates only remotely, using rockers or rods. This design feature also has its pros and cons:

The lever is located more comfortably for the driver, since its position does not depend on where the manual transmission is located;
The vibration that is created in the gearbox is not transmitted to the gearshift lever;
Opens up a wide field of activity for automotive designers, who can place the gearshift lever in any place convenient for them.

The disadvantages of this design are as follows:

A more technically complex system requires more attention and is less durable;
After long-term use, backlashes often appear;
There is no such clarity of gear shifting as in the version with a gearbox on a rear-wheel drive car;
From time to time it is necessary to adjust the thrust, which may require qualified intervention from car service specialists.

Advantages and disadvantages of manual transmission

Any system, including a gearbox, has several different designs with various pros and cons. Let's look at how manual transmission differs from other types of transmission:

The main advantage of using a manual transmission is its price. Most budget cars are equipped with mechanics. Of course, you shouldn’t expect a six-speed manual transmission or the latest seven-speed manual transmission (such boxes are sometimes mistakenly called seventh-generation gearboxes) to be installed on a public car;
If we compare a manual transmission with hydromechanics, then the manual transmission will be much lighter in weight and have higher efficiency;
Manual transmissions do not require the same cooling as automatic transmissions;
Simplicity and reliability of the design (even in the version with a manual transmission for cars with front-wheel drive);
Cars with manual transmissions are more economical than those with automatic transmissions (this does not apply to the latest automatic transmission models, which may be more economical than manual transmissions);
Repairing a car with a manual transmission is not difficult and can be done independently;
Manual transmission is more suitable for sports cars, allowing the use of extreme driving techniques, controlled skidding, and so on;
A car equipped with a manual transmission can be started by pushing, and if that doesn’t work, then it can be towed to any desired distance.

The disadvantages of manual transmission are as follows:

Changing gears takes longer than when using an automatic transmission, since the engine and transmission are disconnected at the moment of shifting;
To change gears smoothly, driving skills with this type of gearbox are required;
The clutch often fails and needs to be replaced;
When driving a car with a manual transmission, the driver gets more tired, as he is forced to constantly change gears. This problem is especially relevant in large cities.

Manual transmission maintenance

Maintenance for a manual transmission usually consists of checking the oil level in it. It is necessary to monitor for leaks on the crankcase, joints and filler and drain plugs.

Cars equipped with an on-board computer can signal to the owner about problems with the manual transmission unit. Each computer signal is decrypted, after which appropriate measures are taken.

The decryption can be in the manual for your car or in a special program on a laptop that can be connected to the car’s on-board system. In most foreign cars, the oil in the box is not changed unless there are any problems.

It is only necessary to check its level occasionally (if there are no signs of leaks).

Manual transmission is a fairly simple and repairable system. If you need a simple and reliable car, then choose a car equipped with a manual transmission.

Source: https://SwapMotor.ru/korobka-peredach/mkpp.html

How the manual transmission works and how it works

A gearbox is a device necessary for every car with an internal combustion engine.

The need for this mechanism is due to the fact that any engine has a rather narrow speed range where torque and power reach their maximum.

And, in addition, each engine has a so-called “red zone” - a speed limit that cannot be exceeded in order to avoid engine breakdowns.

A gearbox is necessary for every car with an internal combustion engine.

This article will be entirely devoted to the topic of gearboxes, namely its mechanical variety (manual transmission).

After all, both an “experienced” driver and a novice car enthusiast need to know the structure of a manual transmission and its operating principle.

The article will also present graphical diagrams of the manual transmission, discuss its main faults and give advice on the correct operation of this vitally important mechanism for the car.

Types of gearboxes

In addition to mechanical, there are other types of gearboxes - CVT, robotic and automatic.

The CVT gearbox is continuously variable. The most important parts of the variator are the sliding pulleys (there are two of them) and the belt that connects them. The connecting belt in section has the shape of a trapezoid. The main advantage of the variator is the constant operation of the car’s engine in optimal mode.

There are also additional advantages, which include dynamic acceleration, smooth movement and efficiency. Compared to an “automatic” (automatic transmission, automatic gearbox), a variator has a very simple design.

But if you compare it with a manual transmission, the CVT is still inferior to it in terms of dynamics and efficiency.

In addition, it is almost impossible to combine a CVT gearbox with a powerful engine, since the fragility of the belt will not allow this. Servicing and repairing a CVT is quite an expensive pleasure; it will be easier and cheaper to replace the gearbox. And another disadvantage is the need for additional mechanisms for reversing and starting.

A robotic gearbox is almost no different from a mechanical one - torque is also transmitted from the engine to the transmission using a classic “dry” single-plate clutch. But there is still such a nuance: in a robotic box, the processes of gear shifting and on/off are automated. clutch.

Therefore, the “robot” can significantly simplify the process of driving a vehicle - there is no need to change gears manually and, wasting precious time, thinking about which gear to engage at a given moment.

You can also add to the advantages of the “robot” box its relative cheapness, efficiency and light weight.

Robotic gearbox diagram

However, there are also disadvantages. The robotic gearbox does not operate very smoothly, and gear shifts occur with a significant delay. In addition, at high speeds, the “robot” can react to shifts with jerks and jolts. Manual mode will not help here, since the clutch is “commanded” by the same electronics.

If you compare a robotic gearbox even with a simple automatic transmission, then the clarity of the “robot” shifts is significantly inferior to the “automatic”. It should also be remembered that when starting to move, a car with a robotic gearbox makes a slight rollback. Based on all the listed disadvantages, manual transmission is traditionally installed on the most “budget” car models.

Mechanical transmission device

Now let's move on to our “hero of the occasion”, to which this material is dedicated – to the manual gearbox.

As you know, a manual transmission is a mechanism that transmits, converts and changes the direction of torque from the engine flywheel.

In “mechanics”, the stages are switched mechanically accordingly - by moving the gear shift lever. Torque is first transmitted to the output shaft and then to the wheel drive.

What is meant by the term “step transmission”? Traditionally, it determines a stable transmission coefficient (the so-called gear ratio) between the interacting gears of the shafts - the driving and driven ones.

This is how a “mechanic” differs from, for example, a variator, where the mentioned coefficient is not tied to the gear ratio and is floating. In other words, the ratio of the number of teeth of the driven gear to the number of teeth of the drive gear gives the gear ratio. These numbers differ at different gearbox levels.

The highest gear ratio is obtained at the lowest stage, and the smallest, on the contrary, at the highest.

In general, the operating principle of a manual transmission is quite simple, and the set of its parts is small

The design of a manual transmission can be called relatively simple. The manual transmission package includes:

shafts with gears (primary, intermediate and secondary);
additional shaft with gears for reverse movement;
crankcase;
synchronizers;
directly the gear shift mechanism, equipped with locking devices and locks;
shift lever.

The crankcase contains bearings in which the gearbox shafts rotate. The shafts are equipped with sets of gears with different numbers of teeth. For silent and smooth gear shifting, synchronizers are used - they equalize the angular speeds of the gears as they rotate.

The operation of the gear shift mechanism is to change gears - this is controlled by the driver using a lever. The locking device allows you to keep the transmissions from unwanted self-switching off.

The locking device is designed to avoid engaging two gears at the same time.

Manual transmission steps and shafts

As mentioned above, the gear ratio is determined through the ratio of the number of gear teeth that interact. For example: first gear = smallest gear = highest gear ratio.

All manual transmissions are divided into types according to the number of stages. There are four-, five- and six-speed manual transmissions.

Nowadays, the most common “five-speed” is a 5-speed gearbox, but a 4-speed one can be found very rarely.

In addition to the number of stages, manual transmissions are also divided into types according to the number of shafts. There are three-shaft and two-shaft boxes. Three-shaft gearboxes are equipped with front- and rear-wheel drive vehicles (including heavy trucks), and two-shaft gearboxes are most often installed primarily on passenger cars with front-wheel drive.

Shafts and gears of a manual transmission

Three-shaft gearbox device

The three-shaft gearbox package includes:

the drive shaft, also called the input shaft, and its gear;
intermediate shaft with gear block;
secondary shaft (driven), also with gear block;
the transmission housing, called the crankcase;
synchronizer clutches;
directly the gear shift mechanism.

In three-shaft gearboxes, as their name implies, there are three shafts - drive (primary), intermediate and driven (secondary).

The drive shaft transmits torque to the intermediate shaft, to which it is connected via a gear. The intermediate shaft is also equipped with a gear block.

The secondary (driven) shaft rotates independently of the primary one, although it is located on the same axis with it and also has a block of its own gears.

The manual gearbox housing is made of light metal. The entire gearbox mechanism is attached inside the housing, and lubricant is poured there (most often gear oil, although nigrol was used in older Soviet-style models).

The location of the shift lever can be different: sometimes the lever is located directly in the box, and sometimes it is mounted on the body. The mechanism responsible for remote gear shifting is colloquially called the “scene”.

Two-shaft gearbox device

The two-shaft gearbox includes:

drive (primary) shaft equipped with a gear block;
driven (secondary) shaft, also with a gear block;
gear shift mechanism;
main gear;
synchronizer clutches;
differential;
gearbox housing

So, this type of manual transmission has only two shafts. In general, the location and purpose of the parts of a two-shaft box is similar to a three-shaft box.

The difference is only in the location of the shafts (they are parallel) and in the principle of creating the transmission - if in a three-shaft it is created by two pairs of gears, then in a two-shaft one pair works.

The two-shaft manual transmission does not have direct transmission. Also, in twin-shaft boxes, not one, but several driven shafts can be used.

For reverse gear, both two- and three-shaft gearboxes use an additional shaft and an intermediate gear. To keep the gear engaged (also for all types of gearboxes), clamps are used. To prevent two gears from being engaged at the same time, a blocking device is provided.

Synchronizers in gearboxes serve to silently engage the gear by equalizing the angular velocity of the gear and shaft. The standard synchronizer package includes two locking rings, a coupling, blockers and wire rings. Using a synchronizer, you can alternately engage two gears of the secondary (driven) shaft.

Simplified diagram of the gearbox operation

Main gearbox breakdowns and their causes

Oil leakage. Most often it can be associated with damage to oil seals and gaskets. The cause may also be a loose housing cover (crankcase). To get rid of leaks, you need to replace the seals and gaskets with new ones and/or tighten the covers.
The gearbox is noisy.

Most likely, the noise of the box is due to a malfunction of the synchronizer. The cause may also be wear of gears, splines and/or bearings. In this case, you should identify the worn parts and replace them.
The gearbox is difficult to engage. This may be the result of a breakdown of one of the parts of the switching mechanism.

Gears and/or synchronizers may also wear out. Check these parts and replace if necessary.
The transmissions turn off on their own. Most often this occurs due to a malfunction of the locking device, as well as severe wear of the synchronizers and/or gears.

The method for eliminating the breakdown is still the same - replacing the locking device, gears, synchronizers - depending on which of them is causing the breakdown.

Tips for operating the gearbox

To ensure that the checkpoint serves you faithfully for a long time, treat it accordingly. The main tip when using the shift lever is to be smart in this process.

Also, do not forget to change the oil in the transmission crankcase from time to time.

If you follow these simple points, the gearbox can last as long as the car itself, without any malfunctions.

Treat the gearbox with care, and it will last for many years without breakdowns.

The majority of gearbox breakdowns are associated precisely with incorrect handling of the control lever. Do not pull the lever with quick and sharp movements - such harsh operation may ultimately lead to a major overhaul of the entire gearbox, since the switching mechanism and synchronizers will fail very quickly (in fact, the same applies to shafts and gears).

Move the lever smoothly, take mini-pauses in the neutral position - then the synchronizers will be activated, which will protect against gear failures.

Don't forget to periodically check the oil level in the crankcase! Top it up if necessary. Also, in due course, a complete oil change will be required - its timing is indicated in the operating instructions for the machine.

Video - Operating principle of a manual transmission

And, of course, classic, always relevant advice: listen to your car! A good driver always feels his iron friend and treats him with care. With this approach, you will not have to repair either the gearbox or other devices of your car.

Source: http://AvtoMotoSpec.ru/poleznoe/ustrojstvo-mexanicheskoj-korobki-peredach-i-princip-ee-raboty.html

What is a manual gearbox?

The transmission system contributes to optimal engine operation. The machine can support the installation of manual transmission, automatic transmission, manual transmission. Cars with a mechanical transmission type are in deserved demand among drivers who have extensive driving experience. This option is found not only on cars that run on gasoline, but also on diesel.

The design of a manual transmission and its purpose

A manual transmission allows for completely manual control of the vehicle. That is why its second name is manual transmission. How does manual transmission work? It works in tandem with the clutch, which allows you to disconnect the engine from the transmission system if necessary. As a result, there is no need to turn off the power unit speed when changing gears is required.

Types of mechanics:

The first type is common among domestic cars. It has compact dimensions, compared to the 3-shaft version, and weighs less. Three-shaft manual transmissions are characterized by the fact that they have a wide power range.

Thanks to this, many trucks and crossovers are equipped with it. The 3-shaft versions include: a driven shaft, an intermediate and a drive shaft.

The intermediate shaft of the gearbox ensures the transmission of rotation from the normally fixed input shaft to the secondary shaft.

2 shaft gearbox3 shaft gearbox

The diagrams of this transmission show in detail all the mechanical connections in the box itself between its spare parts, help to understand the principle of operation and gear shifting.

Operation of manual transmission

What is the operating principle of this device? It lies in the fact that the moment of force of the power unit changes in steps due to the influence of gears.

It should be noted that the box (in addition to gears) includes a crankcase, input/output/intermediate shafts, synchronizers, including a mechanism that ensures gear shifting.

Their overall interaction on the vehicle guarantees the effective transfer of torque.

The synchronizer is installed between the driven and drive shafts. The diagram of this mechanism allows you to see that it consists of the following elements: hub, coupling, crackers, locking ring and wire ring.

The working material from which the synchronizer is made is steel or brass; less common are car models where the synchronizer is made of carbon.

It is able to withstand high temperatures and guarantees reduced noise levels.

The primary and secondary shafts of the gearbox effectively cope with heavy loads. The input shaft of the gearbox accounts for the moment of force of the engine crankshaft.

The manual transmission housing contains a lubricant that reduces friction of metal components, thereby increasing the life of the transmission system.

Number of steps

The number of steps that a manual transmission can include varies mainly from 4 to 6, but there are also 7-speed cars. Each speed level on a manual transmission provides the required gear ratio of the shafts inside the box itself. It should be noted that it is the five/six-speed versions that are quite in demand among car enthusiasts. The first six-speed manual transmissions appeared in the 1990s.

The stages are switched using a special lever. In this case, the resulting moment of force is transmitted to the secondary shaft of the gearbox, then to the existing wheel drive. Neutral gear is present.

When it is turned on, the gears rotate freely. The shaft rotates at a frequency identical to that of the drive wheels. The neutral position should be switched to when stopping.

As a rule, neutral is the middle position of the installed gearbox.

Features of operating a car with manual transmission

It should be noted the main advantages of manual transmission:

allows you to achieve maximum speed;
allows you to change the gear ratio of rotation speed from the power unit on the car to the installed wheels;
rapid acceleration is carried out;
the maximum torque is ensured;
acceptable fuel consumption;
it seems possible to switch to reverse mode;
The car can be started by coasting.

To ensure that the resource of this transmission option does not expire prematurely, the manual transmission device must be serviced in a timely manner. In particular, you should promptly change the oil, which is constantly getting dirty and other foreign particles.

Also, the driver must adhere to certain rules for operating the vehicle. For example, pressing the clutch pedal when the car is on a slope. This cannot be done with a manual transmission.

This will cause damage to the car system.

Switching between gears and leaving your foot on the clutch pedal is also not recommended.
When compared with an automatic transmission, repairs to manual transmissions will cost the motorist less. Spare parts for manual transmissions are widely distributed on the automotive market; motorists will not have any problems finding and purchasing them.

Source: https://prokpp.ru/pro-korobku-peredach/mehanicheskaja-korobka-peredach.html

IT News

DateCategory: Transport

The gearbox, or transmission in other words, transmits the rotational force - the so-called torque - from the car engine to the wheels. Moreover, depending on the driving conditions of the vehicle, it can transmit torque completely or partially.

A car going uphill should be in a lower gear than a car going down a flat highway. With a lower gear, more torque is transmitted to the wheels. And this is required when the car is moving slowly because it is hard. Higher gears are suitable for driving the car faster.

There are manual transmissions, but there are also automatic ones. To change gear in a manual transmission, the driver first presses the clutch pedal (picture on the left). In this case, the engine is disconnected from the gearbox.

Then the driver moves the control lever to another gear and releases the clutch pedal. The engine is reconnected to the gearbox and can once again transfer its energy to the wheels.

In an automatic transmission, the position of the gas (accelerator) pedal is correlated with the speed of the vehicle, and the gear is automatically changed if necessary.

Manual transmission control

The accompanying diagrams show how the control lever can be used to change from one gear to another. Depending on the gear installed, different shares of torque, passing through the gearbox (red lines with arrows), reach the wheels. Neutral gear. Engine energy is not transferred to the wheels.

Neutral gear. Engine energy is not transferred to the wheels.

First transfer. The largest gear on the drive shaft is connected to its pair on the driven shaft. The car moves slowly, but can overcome difficult sections of the road.

Second gear. The second pair of gears works together with the clutch mechanism. In this case, the vehicle speed is usually from 15 to 25 miles per hour.

Third gear. The third pair of gears works together with the clutch mechanism. The speed of the car is even greater, and the torque on the wheels is less.

Fourth gear. The input and output shafts are connected directly (direct drive) - the vehicle speed is maximum, and the torque is the lowest.

Reverse (5th gear in the picture) When reverse gear is engaged, its drive gear rotates the output (drive) shaft in the opposite direction.

Accelerator operation

The engine speed per minute depends on how much fuel flows from the carburetor into the cylinders. The movement of fuel is regulated by the carburetor throttle valve, and the operation of the throttle valve is controlled using the accelerator pedal, which is located on the floor in front of the driver.

When the driver presses the accelerator pedal with his foot, the throttle valve opens and more fuel flows into the engine. If the driver releases the accelerator pedal, the throttle closes and the amount of incoming fuel decreases. At the same time, both engine speed and vehicle speed decrease.

Automatic transmission

When an automatic transmission is used, the driver does not have a clutch pedal under his foot. Instead, a torque converter paired with a planetary gear (picture on the right and below) automatically disconnects the engine from the drive shaft when driving conditions require changing to another gear.

And after the gear has changed, the drive shaft is reconnected. As soon as the driver puts the control lever in the operating position, the automatic transmission mechanism itself will select the desired gear in accordance with the driving conditions of the car at the moment.

Source: http://Information-Technology.ru/sci-pop-articles/27-transport/6134-ustrojstvo-i-printsip-raboty-korobki-pere

Purpose and design of a car gearbox

The gearbox serves to change the traction force on the wheels of the car depending on the resistance to movement and gives the car the ability to move in reverse. The gearbox also allows you to disconnect the vehicle's drive wheels from the engine when switching off gears, thereby ensuring the ability to start the engine and allow it to idle.

A gearbox is a mechanism consisting of a set of gears that can be meshed in various combinations.

Each combination of transmission gears is called a stage or gear. The number of stages (gears) in the gearbox depends on the design of the car and is usually from three to five (not counting reverse gear). Accordingly, transmissions are called three-speed, four-speed and five-speed.

The engagement of different pairs of gears is carried out using carriages (gears) moved along the shafts of the box. Depending on the number of movable carriages, boxes are divided into two-way (two carriages) and three-way (three carriages).

The principle of operation of automobile gearboxes

The operating principle of automobile gearboxes, regardless of their design and number of gears, is the same. Let's consider their design and operation using the example of a three-speed two-way gearbox of GAZ-69A and GAZ-69 cars.

The primary (drive) shaft 23 is integral with the third gear gear 20 and the ring gear 19. The primary shaft is connected to the engine crankshaft through the clutch.

The secondary (driven) shaft 6 is like a continuation of the primary shaft and is located on the same axis with it. The secondary shaft shank sits in a roller bearing 21 mounted at the end of the primary shaft. As a result, the secondary shaft can rotate independently of the primary one.

Two gears 8 and 11 and a gear hub 16 are installed on the secondary shaft. Gear 8 (carriage) sits on the shaft on splines and can move along its axis. Gear 11 has a ring gear 13. It is mounted on the secondary shaft on a bronze bushing 12, so it rotates freely on the shaft. A carriage 14 for second and third gears is installed on the hub, which moves along the hub.

Intermediate shaft 31 is a block of gears 27, 29, 32 and 33, freely rotating on axis 30.

The reverse intermediate gear 34 is mounted on the axle on a bronze bushing and rotates freely on the axle.

The primary and secondary shafts are installed in the sockets of the crankcase on ball bearings 22 and 3. The axis 30 of the intermediate shaft is fixedly fixed in the crankcase sockets, while the intermediate shaft 31 rotates on an axis on roller bearings 26. The axis of the reverse intermediate gear is fixedly fixed in special crankcase sockets.

The input shaft gear 20 with the intermediate shaft gear 27, as well as the gear 33 with the reverse intermediate gear 34, are in constant mesh.

The intermediate shaft gear 29 and the secondary shaft gear 11 are also in constant engagement.

The carriages 8 and 14 can move along the secondary shaft and be engaged: the carriage 14 with its internal teeth with the ring gear 19 of the gear 20 of the primary shaft or with the ring gear 13 of the gear 11; carriage 8 with gear 32 or 34.

With the carriages in the position shown in the figure, torque from the engine will be transmitted from the input shaft through gears 20 and 27 to the intermediate shaft gear block.

However, torque will not be transmitted to the secondary shaft, since in the position of carriages 8 and 14 shown, the secondary shaft is disconnected from both the primary and intermediate shafts. This position of the carriages is called neutral. The carriages are placed in the neutral position when the engine is started and the engine is idling (at a standstill or when the car is coasting).

To set the car in motion, torque must be transmitted to the secondary shaft.

To do this, carriage 8 or 14 should be brought into engagement with one of the intermediate shaft gears, which would ensure the highest gear ratio, and therefore the highest torque on the secondary shaft.

Move carriage 8 to the right and engage it with gear 32 of the intermediate shaft, as shown in Fig. A. This position of the carriages corresponds to first gear.

To engage second gear, it is necessary to disengage carriage 8 from gear 32, and then, moving (to the left in Fig. b) carriage 14, engage the latter with ring gear 13 of gear 11, which is constantly in mesh with gear 29 of the intermediate shaft.

You need to change from second gear to third in the same sequence as from first to second gear. In this case, the carriage 14 is disengaged from the gear ring 13 of the gear 11 and is brought into engagement with the ring gear 19 of the gear 20 of the primary shaft (Fig. c), the primary and secondary shafts begin to rotate as one.

To move in reverse, both carriages should be moved to the neutral position, and then carriage 8 should be moved to the left and engaged with the reverse intermediate gear 34. In this case, the direction of rotation of the secondary shaft will change to the opposite.

For easy and shock-free gear shifting, it is necessary that the peripheral speeds of the gears being engaged are the same.

The peripheral speed of a gear depends on the number of revolutions of the shaft on which it sits and on its diameter: the larger the diameter of the gear and the number of revolutions of the shaft, the greater its peripheral speed.

To facilitate shockless gear shifting and reduce wear on gear teeth in gearboxes, in particular in the gearbox of GAZ-69A and GAZ-69 cars, a special device is provided - a synchronizer for the second and third gears.

The synchronizer equalizes the peripheral speeds of rotation of the gears before engaging them. It is arranged as follows. At the end of the secondary shaft 1, the gear hub 6 of the synchronizer is mounted on splines and secured with a retaining ring 14.

On the outer teeth of the hub there is a carriage 10 of the second and third gears, covered by a fork 8. In three grooves of the hub there are sliders 11 of the blocking device, connected by means of balls 9 clamps with the carriage 10. Locking bronze rings 4 are located on both sides of the hub.

Each blocking ring has a toothed rim and grooves 47 for sliders; The inner surface of the ring is made cone-shaped.

The synchronizer is located between the ring gear 13 of the gear 15 of the input shaft and the ring gear 3 of the gear 2 of the second gear. The bases of the ring gears of gears 2 and 15 have conical surfaces.

When the second or third gear is engaged, the synchronizer carriage 10, using a switching device, moves together with the sliders 11 along the hub 6. The sliders, which fit into the grooves 17 of the locking rings 4, press the ring against the conical surface of the corresponding ring gear.

Due to the friction that arises between the contacting conical surfaces, the locking ring moves slightly in the direction of rotation of the ring gear until the grooves touch the side surfaces of the sliders. At the same time, the surface is beveled.

the ends of the teeth of the carriage 10, resting against the beveled surface of the ends of the teeth of the ring 4, prevents the teeth from engaging, as a result of which the ring 4 is strongly pressed against the conical surface of the ring gear.

As a result of the strong friction of the cones, the speeds of rotation of the shafts are equalized, the carriage 10 moves further, squeezing the balls of the 9 clamps, and with its teeth it enters the spaces of the teeth of the crown 13, silently engaging the corresponding gear.

The gearbox is controlled using lever 6; swinging in the ball joint of the gearbox housing cover.

In the same lid, two sliders 3 and 12 are installed in the sockets, which can move along their axes, while sliding in the sockets of the box lid. Each of these sliders is connected to a fork: slider 12 of the first gear and reverse gear with fork 11, slider 3 of the second and third gear carriage with fork 10.

The ends of the forks fit into the annular grooves present in the carriages and do not interfere with the carriages rotating freely along with the secondary shaft. When the forks move longitudinally, the carriages move along the shaft and thereby engage the corresponding gears. By moving the lever, and therefore the forks and carriages, the gears in the box are changed.

To prevent arbitrary switching off of gears and simultaneous engagement of several gears, the gear shift mechanism is equipped with special devices - clamps (stoppers) - to fix the lever in a certain position and locks that do not allow several gears to be engaged simultaneously.

In three-speed gearboxes with two sliders, the latch also serves as a lock.

The retainer consists of two hollow crackers 13, sliding in a special socket made in the gearbox cover. Under the action of spring 1, the crackers slide into the recesses located in the corresponding places of the sliders. The crackers reliably hold the sliders from spontaneous movement, and also prevent the possibility of simultaneous movement of both sliders.

It is impossible to move both sliders at once and engage, thus, two gears at the same time for the following reason.

As soon as one of the sliders moves enough that the cracker comes out of the recesses, both crackers will be pushed close to each other.

The total length of the shifted crackers is selected so that the second cracker will no longer be able to come out of the recess of the slider adjacent to it and thus the slider is securely locked.

To prevent accidental engagement of reverse gear, in the gearbox cover, slightly below the ball joint, there is a release bracket 4 with a spring 5 pressing on the end of the lever 6. Therefore, to engage reverse gear (and first gear), increased force must be applied to the lever so that move the bracket to the side.