Gearbox: explained by an expert mechanic

The gearbox is the secondary drive of an automobile. It powers the engine. The engine is the first drive because when an angular velocity of a car wheel revolves, the gear is engaged. The gear then becomes the secondary drive. The third or final drive is the axle or differential.

A gearbox is a transmission device. It is essential in moving a vehicle from one point to another. The gearbox performs a significant function in transmitting the power from the engine to the wheels. Another function of the gearbox is to increase or reduce speed in a vehicle.

Components of the Gearbox

Components of the Manual Gearbox

The gearbox to a technician is all about maintenance. To a car owner or driver, it is about the principles of how the gearbox operates. He takes note of the gear movement and the engine.

In an automatic car, the important terms in the gearbox are:


(Here, a manual drive is available where one can switch between gear 1 and 2.)The gearbox in a manual car usually has 5 or 6 gear levels asides from the Reverse gear. The 1, 3, and 5 gears are in front while the 2, 4, and 6 are behind. The gearbox has both internal and external components.

The internal component of the gearbox

This include

  • The convertor:  This serves as a clutch base for the gearbox.
Gearbox converter
  • The gear teeth: This is where the addendum and dedendum merge for transmission to take place.
The gear teeth
  • High gear drive: This is the secondary drive shaft that links the gear and the engine.
High gear drive

The high gear drive has a basement where the clutch plate fiber, sun gears, bearings for easy transmission, valve body which house the solenoid is being inserted.

  • The Seals: it protects the transmission fluid from moving beyond its boundaries. There are boundaries between each of the components.
  • The synchronizer: The component that transmits the gear teeth from point A to point B.
  • The valve body: It contains the solenoid and some of the electrical wiring circuits.
  • A filter filters any debris that comes in. A filter ensures it doesn't transmit dirt to the internal components preventing it from shutting down. It sits where the solenoid and valve body is based.
  • The crown wheel: It contains the gear teeth.
  • Clutch fiber: It has two sides inside the gear; metal and asbestos side.

If the asbestos side turns to be metal, the gear will be engaged but will not transmit, and the vehicle will not move. This scenario shows there is a problem with the fibers or speed sensors.

The speed sensors are of different types. When there is a problem with the fibers, the vehicle will not move. You will have to toll it to a mechanic. Other internal components include Sun gear, Bevel gear, the bearings, and the sprocket.

After assembling the internal components, it is being put into housing and sealed up. Also, after building the internal element of the gearbox, a polymer is used to wrap it up so that the fluid will not get into the elements inside the component.

The external component of the gearbox

This include:

  • Aluminum-based housing: This is the casing that houses all other components. It contains the convertor, high gear drive, the bevel gears, the gear teeth, the bearings, the sun gear, the seals, the synchronizers.
  • The sensors: This is on top of the aluminum base.
  • The module: This is by the side of the aluminum base.
  • Seal: This is by the two edges of the aluminum base, preventing leakage from the driving shaft. There are usually two of them, and the second seal prevents transmission fluid from flowing from the convertor to outside the gear. Once the transmission fluid from the converter leaks, there will be a shortage in the gear system, which will result in the gearbox having issues.
  • External control cables: it links the gear to the selector handle. The control cable will control the gear from inside, changing the gears from 1 down to 6.

In the external component, the power transmitted from the battery, which makes the gear work, is installed. The gear has some modules or sensors on top of it. The power source is linked to those sensors.

When the car ignites, the power moves through the sensors, and the vehicle starts moving. After assembling the external components, it is fixed on the engine. Some millimeter bolts surround it, which guides it, and the gear is linked to the selector handle with the external control cables.

When all these are in place, the gearbox remains fixed on the drive stand and starts moving. When neutralized and sent to the drive stand, it remains fixed and keeps moving.

Types of Gearbox

We have automatic and manual drive gearbox.

Manual Drive Gearbox

Manual Drive Gearbox

The manual drive gearbox is purely mechanical-based. Everything is done manually. The components are mechanical. The stick helps to position from gear 1 down to gear 6. The hands are actively involved in the control of the gearbox.

Automatic drive gearbox

Automatic drive gearbox

This is unique and complicated because it is electronically and mechanically based. It is majorly electronically based. When the power goes into it, it ignites the electronic component, and then the mechanical component starts functioning.

When a car is put on "drive," that is the only thing done manually.

Once it accelerates, every other part functions electronically. The electronic components like the solenoid start transmitting from gear 1 down to gear 6.

However, it depends on the number of gears on the vehicle driven.The electronic component changes the gears following the speed of the car. When the car decelerates, the gear will automatically return to gear 1.

The automatic drive gearbox has two drives, which are: 4-wheel drive and 2-wheel drive. In the 4-wheel drive, the final drive called the axle or differential is inbuilt. It cannot be separated. When power moves from the synchronizers, and the gear is engaged. The sensors ignite the fibers, and once you initiate the brake, the vehicle starts moving.

The difference between the manual and automatic gearbox is the electronic components, while other components are similar. Another difference is that there is a clutch fiber control in the internal base of the automatic gearbox but not in the internal base of the manual gearbox. In the manual gearbox, it is outside the gearbox, attached to the angular velocity of the car wheel drive.

Advantages of an Automatic gearbox

  1. Easy drive
  2. Less stress
  3. Speed

In terms of speed, the manual gearbox will always engage first. Still, the Automatic gearbox, when engaged and accelerates, speed will surpass that of the manual gearbox because before the person using a manual gear decides to change from gear 1 to 2, the Automatic car is already ahead.

The Automatic gear is faster because the gear switching is automatically programmed, while for Manual gear, human factors affect it. Comparing the speed of vehicles can be actualized when they both have the same RPM level and speedometers. For instance, a vehicle with a 24 pin gear system, the RPM, which is about 280, cannot compare to a five-pin gear system.

Cars from 2013 to 2014 have automatic gearboxes. You will hardly find vehicles from 2013 having a manual gearbox sitting in them.

Gear acceleration pins

These are components that enforce speed. Pins vary with the capacity of engines and gears. Toyota from 1999 to 2003 have 5 to 9 pins gear. Cars from 2005 upward have 13 to 24 pins gear. The velocity of the latter will increase, which needs a higher electronic transmission unit to be able to pull the load of the car.

Pins are electronic transmission units. The higher the number of pins, the higher the velocity. When the pins increase, the components in the gear and the engine also increases. This process helps to build it up to the required velocity. Every car uses pins that suit its size.

Transmission Fluid

After handling the installation of the gear components, the next important concept is the transmission fluid. Transmission is the movement of an object with the aid of a fluid.

Transmission fluid serves as the lubricant to the gear system. The gear components do not need any form of friction; they need fluid to function. It is only the fluid that can allow the gear to transmit freely. The fluid varies in quality. The higher the quality, the higher the duration. Good transmission fluid can stay for about 4 – 5 years. E.g., WS ATF Toyota.

Fluid is an essential part of the gearbox because it can't function well without fluid. The fluid lubricates the mechanical component. Fluid is universal for mechanical and electrical components. The transmission fluid is important in gearboxes for reducing friction and wear between the gear teeth and also helps to dispel heat.

Every gear or automobile component has a system that diverts. by implication, this means whatever flows around. It returns to its initial state. Provided that there is no leakage, it won't go out. The fluid remains inside the system until the lubricant is no longer active, bringing about excess friction. When this happens, you must change the lubricant.

Drive functions of a gear

Before starting your car, ensure the gear is on point P- Park if you drive an automatic transmission automobile. If the gear lever is not on Point P or neutral, the car won't start.

Furthermore, if it is neutral, the car will start, but the key will not go out. If you struggle to remove the key, when starting the car again, it won't start until the gear lever is put on P- Park. A vehicle can only start when the gear level is on Point P – Park.

When the gear is at Point P – Park, start the key and put your foot on the brake pedal. After applying the brakes, take hold of your gear, the first return in reverse. Release your legs from the brake and press the accelerator.

To drive, go to drive; you will pass the neutral point and move to D - Drive with Your legs on the brake. Release your leg from the brake and press the accelerator. After all, these are in place; the electronic control driving holds the fort.

All you need to do is to control the car and keep accelerating. When you decelerate, the car's speed will reduce. In the same way, when you accelerate, the car's speed increase. We have two types of starting units; keyless and key-starting units.

keyless and key-starting unit

Keyless starting unit: Before starting the vehicle, you must engage the brake pedal.Key starting Unit: You don't need to apply the brake when you start the car. After starting the car, you then press your brake pedal. The brake pedal now handles both the gear acceleration and the reduction of speed. For a manual vehicle, you make use of the clutch pedal.

Changing of gear

From gear 1 to 2, your RPM will read 2.5 or 3 bar in changing gear before it changes to gear 2. After it has crossed 3 bar to 4, it changes to gear 3.The automatic gearbox works at its own pace; you can't force it.

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Helpful practices

  1. What to do when your gear disengages?

When driving and you discover your gear disengages, and the handle is moving freely, no cause for alarm. It could be a result of the gear cable losing its connection from the base.Just park your vehicle. In between the engine and the gear before the driveshaft, you will see the control unit. You can manually engage it and take it to a nearby mechanic workshop to fix the gear cable.

A quick fix: When your manual stick is free, please park your vehicle, open your bonnet. The temperature will be high because you were in motion, so allow it to cool. Then, Close to the steering rack (facing the engine, it's by your right side), you will see the air filter base.

Behind it, where the gearbox is, you will see the manual control system. All you need to do is to engage the accelerator handle. It will start making some sounds. Put your ignition on, set it manually, and look at the signal button in the car, which will show N, R, or D. When it gets to D - Drive, you can drive your vehicle comfortably to where you can fix it.

  1. How to know when your gearbox is faulty?    

The engine's sound will become pronounced when you accelerate, but the car will not move according to acceleration. Your control handle moves, for instance, from reverse to drive, but the vehicle doesn't move. When you engage your gear, it shows that the control unit is in place, but you accelerate, and the car doesn't move.Therefore, it is worth noting that there are other five relative clauses when there is a fault in your vehicle. It could be the cable control. It could be a problem with the brake system.

  1. When your gearbox is slipping, what does it indicate?

When this happens, no need to worry that it's an expensive gearbox failure. The above indicates a leakage in the transmission fluid or the transmission fluid is not appropriate.

This fault is easy and inexpensive to fix. If your gears are slipping, you have to fix them immediately as it is dangerous to drive a car with slipping gears. Several reasons can cause leakage. It could be a loosened bolt that needs tightening in the gearbox system. You can do this yourself or seek professional help.

  1. When your clutch is making an unusual type of noise when changing gears, what does it indicate?

When you hear an unusual sound when changing gears, this could be a sign that there is an issue with your clutch. If there is a problem with your clutch, you will find it difficult to change gears.

This fault could mean you need to change a part of your clutch. Some parts may wear out and need fixing. Then again, your transmission fluid might need replacement. If you're knowledgeable in this area, you can repair this yourself. Though, it is best to take your vehicle to a professional.

What type of energy is in the gearbox?

What type of energy is in the gearbox

It is kinetic-based energy that converts to heat energy.

Are transmission and gearbox the same?

Transmission is a process in the gearbox. When you engage the gear with the presence of the fluid, the sprocket rotates and transmits the power that is the transmission.

Another instance, when you ignite a car and the angular velocity of the car wheel rotates, it also transmits power which also is the transmission. So it is safe to say that a gearbox is a transmission device. The gearbox performs a significant function in transmitting the power from the engine to the wheels.

Preventive Maintenance

Some of the vehicles from 2013 upward do not have a gauging or deep stick to check your fluid level. It is ideal to always check your fluid level in the gearbox. When checking your fluid level on your gearbox with a gear that has a deep stick, check your gauge when the engine is on.

That is when you get a good level of transmission fluid. You get the perfect level of the gauge when the device temperature is still high. Check the engine side when the temperature is cool.

Once your fluid is short, there will be issues with your gear selections. If you're using a low-level transmission fluid, ensure that when the period of its use is getting to an end, you check the viscosity of the transmission fluid and replace it to save the life of the engine.

Preventive maintenance save cost than predictive maintenance. The best way to avoid spending so much on repairing your gearbox is to detect issues early.

Some practices you can adopt include:

  • Listen to your gearbox for any noise: Inside the gearbox is a hub that can make any noise if it's not working. Buzzing, clicking, and jerking are signs that you need to give attention to your gearbox, and it will likely continue to break down without professional help.
  • Does your gearbox smell like it is burnt? Burning out is not something strong gearboxes do. If you smell a burning smell in the gearbox, it means that the oil in it is burning for some reason. This one is not a job for an amateur mechanic and requires special attention to fix it. Take the car to a professional to have it checked and repaired.
  • When your gearbox feels different: if you have been driving happily for years and the gearbox doesn't feel right, have it checked.

You know your car better, and if you think something is wrong with the oily parts, you are probably right. Gearboxes are complicated, but their problems aren't always a death sentence for the vehicle.

You have to check it as soon as possible to give you the best chance and lowest price. You can also see our article on the Steering box system to further enhance your knowledge on this topic.

Key Takeaways!

  • A gearbox is a transmission device comprising of has both internal and external components. The types of the gearbox are Manual and automatic gearbox.
  • The manual gearbox is mechanically based, while the Automatic gearbox is both mechanically and electronically based.
  • People prefer the automatic gearbox over the manual gearbox because it is easy to drive, it has less stress, and it is faster.
  • Transmission fluid serves as the lubricant to the gear system. It helps reduce excess friction.
  • A vehicle can only start driving when the gear level is on Point P – Park. The automatic gearbox works at its own pace; you can't force it.

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