What is the gearbox and what is its function?

The car’s gearbox is a basic component, which is responsible for helping the engine’s power to be transmitted efficiently, while protecting the elements that are part of it. A basic element of the vehicle that should be known in depth.

Spain is a country where almost all cars have a manual gearbox. However, in other countries, vehicles with an automatic gearbox are common, as is the case in the United States. In both cases, the vehicle’s gear change is a fundamental part for the car to drive as it should and make the most of the engine’s power, transferred to the wheels through the vehicle’s transmission.

This piece does not require regular maintenance, since the only operations that are carried out on it are carried out in a workshop, when a breakdown occurs. A problem that we can avoid if we know how the gearbox works and how to take care of it properly.

Parts of a gearbox

To get to know this element of your vehicle, we start by analyzing the different parts of the gearbox. This box has a series of toothed wheels or gears, which are located on two or three different shafts, depending on the model. The first of these axes is the primary one, which receives revolutions directly from the engine and rotates at the same speed and direction as the engine.

The second element is the intermediate one, which meshes with the primary shaft and rotates in the opposite direction to the engine. This element is not present in the transverse boxes, but it is in the rest, most of them. The third element is the secondary one, which is the one that introduces the gears responsible for the movement of the motor, through a system of sliding gears . Depending on whether the box is longitudinal or transversal, then this gear will rotate in the same or in the opposite direction.

All these elements, together with the reverse gear shaft , are located inside a casing. This is made of high-strength metal and is placed on a closed box. It is filled with gearbox oil, to facilitate the movement of the parts. Finally, we have the gear lever, located in the passenger compartment and with which to control the gears of the car to your liking.

Types of gearboxes

As we have already mentioned, we have two large groups of gearboxes. The first is that of the manual gearboxes, which have a gear lever, a clutch and two or three different axes for turning, depending on its design.

For their part, automatic boxes have two main varieties. One of them is the piloted boxes, which have two clutches and an electronic management system for both these clutches and the gearbox itself. The other option is automatic gearboxes with a torque converter. They are heavier, yet always have the next gear ready, reducing the time needed to shift.

How does a gearbox work?

The operation of the gearbox depends on whether the vehicle has a manual or automatic transmission. In those with manual transmission, it will be necessary to fully depress the clutch and move the gear lever to the desired position. Then we released the clutch and got back into rhythm. In this whole process, we are moving the disc of the desired speed, which is put in place by moving the lever. This disc engages with the motor shaft once the clutch is released . A task that is helped by the gearbox synchronizer, which equalizes the speed of the rotating elements to make this union easier and smoother.

For its part, the clutch pedal disappears in cars with automatic transmission, in which it is the box itself that is in charge of moving the gears and the clutch as required by the speed at which we drive. However, in the automatic gearboxes we find a gear selector, which helps us to choose if we need more speed or more power, as well as to indicate when we need to use the reverse gear or the parking brake.

Gearbox failures

To close this analysis, it is time to find out what are the main faults that gearboxes have, both manual and automatic.

Starting with the manuals, a common problem is noise when putting the gear in, which may be accompanied by jerks or “scratches”. This may be due to clutch misalignment or wear. If the clutch isn’t right, it’s harder to get into gear. In any case, it is key to press the clutch pedal well when making changes.

It can also be difficult to put the gear in place, which may be related to a lack of lubrication in the system or to a defect in the linkage system. To solve it, it is necessary to review the entire system of the box. 

If when engaging a gear it is blocked, this is due to the wear of the safety bobbins. If these elements are worn, it is possible that the derailleur tries to engage two gears at the same time. If this happens, the system is locked, for security reasons. This fault is solved by changing the worn bobbins for new ones.

As for vehicles with automatic gearboxes, the usual thing is that the gears slip or there are acceleration problems. This is related to lubrication problems or a fault in the torque converter, which prevents the gears from meshing properly. Finally, if the gear change does not work, the cause is usually a failure of the selector control.

All these breakdowns, especially in manual gearboxes , can be avoided . To do this, simply step on the clutch well when putting the gears and manipulate the gearbox. It is also important not to have the clutch depressed or use the gear lever as a hand rest. These two bad habits cause looseness in the gearbox system and generate breakdowns in the medium and long term.