The gearbox is one of the fundamental parts that every vehicle must have as the only one that has the ability to make a car can, for example, go up a slope and not only move in a straight line. It is essential to be able to maintain good resistance in the engine and for it to have the necessary strength and power that allows it to maintain a constant speed.

What is the gearbox?

The gearbox is a part of the engine of a car that is responsible for transferring torque to the wheels so that they manage to stay in motion so constant .

  • Gearbox Features
  • What is it for
  • Gearbox types
  • Parties
  • How the gearbox works
  • Breakdowns
  • Maintenance
  • Importance

Gearbox Features

Among the most important characteristics that can be observed in a gearbox are the following:

  • The gearbox is characterized by providing different types of gears that act depending on the situation, whether you need to start the car flat , on a slope or to go up a hill .
  • It is located between the engine and the transmission , just after the clutch .
  • Manual-type gearboxes have between five to six speeds and a specific one for reversing .
  • The lever that is responsible for operating the gearbox is operated by the person driving the car.
  • Its most common design is the constant gear type which has three different types of shafts: the input shaft, the intermediate shaft and the main shaft.

What is it for

The gearbox is a part of the transmission system of the car or vehicle that serves to establish an adequate force in order to adapt to the needs that arise while traveling along a road. It is used to decide the type of force and speed that a vehicle can have when it is rolling on the road, which at the same time can be very varied.

Gearbox types

There are two types of gearboxes, each of them have different characteristics and are as follows:


This type of gearbox depends on the coupling and transmission mechanism . There are, depending on the type of gear and the gear ratios, three different manual gearboxes. They are also made up of a single or multiple disc clutch and a gear system with straight teeth.

  • Straight teeth : they are more robust and make it possible to change gears without using the clutch. They are quite noisy and do not have a timing mechanism.
  • Helical teeth : its teeth are inclined following the shape of a helical curve. They produce less noise and have intermediate discs called siros that make their operation simpler.
  • From epicyclic gears : changes are achieved by varying the rotational speeds on the epicyclic sprockets.

Automatic box

In this type of box, the driver does not need to change manually as the clutch works autonomously . In this type of box there are also several types of systems:

  • Conventional automatic gearbox : it has epicyclic trains and a torque converter, it weighs more and has great energy losses so it is hardly used.
  • Robotic manual gearbox with simple disc : it is a manual system to which a clutch made up of solenoid valves and a unit that controls the clutch is added.


The parts that can be found in the gearbox are located in trees and are the following:

Primary tree

This group is responsible for receiving the speed of rotation motor in the same direction. It is here where you can find the sprockets that are responsible for driving the primary and rear traction . They are boxes of longitudinal shape and receive the movement in the same direction as the rotation of the motor.

Intermediate shaft

This type of tree only exists in longitudinal type boxes . It has a pinion geared to the primary shaft and can fit very well with the secondary depending on the type of gear that is selected.

Secondary tree

It produces a rotation in the opposite direction to the motor when there are transverse changes and in the same direction. It is composed of different types of gears that are attached to the shaft by means of a system of toothed units that can move.

Reverse axis

It has a toothed and straight-shaped pinion that is placed between the shafts to avoid reversing the normal direction of rotation produced by the secondary shaft, and it also closes the electrical contacts that activate reverse gear.

How the gearbox works

The gearbox works from the moment the car starts its march , gaining speed and strength . When one of the gears is selected on the gear lever, a selector of axles is immediately activated which are moved thanks to the motor. It has a device that synchronizes the changes until the speed of the gears is equalized.

First gear will make the wheels turn at about a third of the engine speed, but with much more force. Subsequently, the gears that follow will serve to increase the speed little by little as they are changed.


Among the main breakdowns that can occur in a gearbox are the following:

  • Clearance between the gears that causes the box to produce excessive noise.
  • Wear of bearings also produce more noise.
  • Failures in the different shift rods that make it difficult to change gears.
  • Use of improper oil .
  • Synchronizers that have been worn out.
  • Clutch defects .
  • Bad condition of the joints .


Maintenance for a manual gearbox is not so extensive and its care is mainly based on taking care of the clutch . This substance should be changed frequently depending always on the recommendations made by the manufacturer. In general , it should be changed after 5 years or 70,000 kilometers . In the case of automatic gearboxes , the amount of oil and hydraulic fluid must be maintained . The internal filter can be clogged by heat and friction damaging the fluid.


It is important because it is one of the essential parts that every transmission system has in a vehicle. Thanks to it, different types of gears can be made, which at the same time makes it possible for speed changes to occur . If it did not exist, a car could not be moved, for example, on slopes or slopes, it would only work in flat places.

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