Understanding the gearbox: how it works & which type you should go for

The gearbox helps to modulate car speed. Lack of maintenance and improper usage expose you to danger. Read up everything you need to know about the gearbox!

A list containing the most important instruments in a vehicle would be incomplete without one thing – the gearbox. This instrument literally dictates the car speed, modulating it at different times to ensure control and safety. It does these basic functions in between a myriad of other factors that come to play.

What is a gearbox?

In modern parlance, the word transmission flies around. This can be a little confusing to one who isn’t abreast with such automotive jargons. A transmission simply refers to a gearbox. Basically, gear and gear trains are ignited by the gearbox to set the car in motion and covert torque.

The term gearbox means different things in both the British and American English Languages. For the former, it refers to the entirety of the drivetrain such as the prop shaft, final drive shafts, clutch and the gearbox itself. However, in American English, it refers to the gearbox itself.

A gearbox is mostly used in vehicles. It channels the internal combustion engine output down to the wheels. The engines are required to produce high rational speed that would ordinarily not be appropriate to start and stop the vehicle. The gearbox brings the higher engine speed all the way down to the lower speed wheel. In the course of this, the torque is increased.


"Gearbox" might differ in meaning in American and British English

Cars aren’t the only vehicles that make use of a gearbox, other automobiles such as fixed machines and pedal bicycles that make use of different rational speeds have a gearbox too.

Speed reducer gearbox - sounds familiar but something wrong?

People can "google" everything and Speed reducer gearbox is a common phrase searched about cars. You may find the term familiar as two words "speed reducer" and "gearbox" often go with each other but in comparison.

Speed reducer vs gearbox, what are their differences?

Our answer: All speed reducers are gearboxes but not all gearboxes can be called speed reducers. As you see above, gearbox refers to gear train between a motor and a piece of machinery but its functions vary. Most of the time it is for reducing the speed of the input or output. In other cases, it can be tooled to increase the input speed.

Speed reducers only apply for the former function: reducing rpm to correct the output speed.

Selecting the right gear motor application

A gear motor is a complete package consisting of a motor and a gearbox. A gear head is added to a motor to prevent excess speeding and increase the output of the torque. There are certain parameters that are very important in gear motors. They include: efficiency (%), speed (rpm) and torque (lb-in).

To get the most of your gear motor, you need to select the application that is most suitable. Doing this entails computing the speed, load and torque requirements.

The gear motor selection process may seem difficult especially at the conceptual design phase. To make this easier, Naijauto.com has compiled key points to guide you in selecting the best gear motor application. They include the following:

1. Requirements for the design

Make it a point of duty to study the design functionality, development requirements, design parameters and product optimization. All these are done in the design assessment phase.

2. Calculations of design

Design calculations are determinants of torque, overhung load, service factor, testing analysis and gear ratio among other things. Getting these calculations right helps you to pick the motor that suits your application perfectly.


Consider the criteria carefully before choosing gearbox!

3. Types of gearmotors

Basic electrical motors are used for the conversion of electrical energy to mechanical energy. Such motors are mostly charged by Direct Current. They include the following: stepper, brushless, gear heads, brushed, planetary gear motors, servo, spur gear motors, brushed and coreless and coreless brushless.

4. Specifications

Having completed the design calculations and defined the application parameters, data gathered are used to find the best gear motor for your application. There are certain specifications to look out for in selecting the perfect gear motor. They include: RPM, power, torque, current, voltage, enclosure restrictions, life expectancy/ duty circle, shaft diameter, length and rotation (CW or CCW).

5. Speed and torque requirements

In order to get the perfect gearmotor size for your application, you need to be aware of your speed output as well as its running torque and starting. You need to ensure that output speed (RPM) and torque are properly matched to the needs of your application.

6. Test

Don’t go to sleep after selecting your gearmotor application. Carry out series of tests to ensure that everything is in good condition. The motor should be able to run well in different conditions.

If after the selection process, you notice that the motor is noisy, too hot, or seems stressed, carryout the selection process all over again. Or better still, get in touch with the manufacturer to be advised on the way forward.

Types of gearbox in motor vehicles

Starting an automobile requires speed. The speed increases when driving up a hill. If moving at high speed on normal roads, there’s no need for high torque as a result of momentum. Hence, changing the speed and torque of the vehicle, at different times, is necessary to adapt to the condition of the road being driven on.  This is where the gearbox comes in. There are different types of gearboxes for different cars. Basically, they come in two forms namely: manual and automatic transmissions.

1. Manual gearbox

As the name implies, different speed and gear ratios are chosen by the driver manually. It requires a high level of engagement during driving to keep the car in control. Amateur or new drivers find manual gear transmission cars difficult to drive as a result of the intricate details.

This is how manual gearbox works!

Manual transmission gearboxes are subdivided into three parts. They include:

  • Sliding mesh gearbox

This is one of the oldest types of gearbox transmissions. There’s a movement of gears on the main shaft to the left or right. They are meshed with suitable gears on the counter to attain various speed levels. The name comes from the process of meshing the gear by sliding. Although effective, a setback of the sliding mesh gearbox is the requirement of high technical skill to operate it. It also wears out easily due to the rigorous mechanical movements.

  • Constant mesh gearbox

This gearbox attained high popularity in the twentieth century. The gears maintain a constant mesh at all times. Main shaft gears rotate freely without interfering with the haft.

  • Synchromesh gearbox

In the synchromesh gear, both gears to be used are joined in frictional contact. This places their speed on an equal level, making the engagement smooth.

2. Automatic gearbox

The automatic transmission is believed to be an upgrade of the manual transmission (See if car with automatic gearbox or manual one is right for you). In this transmission, all speed levels are controlled automatically by the vehicle. The driver doesn’t have to worry about doing that manually. He/she is only concerned with the general car movement – forward or reverse. You just press or depress the accelerator, and the car will give you desire speed.

There are two types of automatic transmissions, they include:

  • Planetary gear or epicycle gearbox

The planetary gear is also referred to as the epicycle gearbox. It is void of sliding dogs. It doesn’t engage gears either. Instead, it builds up varying gear speeds when it tightens brake bands on the gear of the drums. It’s made up of sun gear, planet gears with carrier and ring gear annular level.

Right at the center (yellow), you’ll find the sun gear. It ensures that the planet gear (blue) receives adequate torque. The transmitted torque is stationed on a carrier that is moveable (green).

The planet gear is known to revolve around the sun, and then mesh together with a ring gear on the outside (pink). There’s isn’t a definite pattern for planetary gear systems. They take different forms from the very basic to the most complex.


How a planetary gear works inside your car (Photo source: Your Mechanic)

  • Hydraulic torque converter

There’s no difference between the hydraulic torque converter and the electric transformer - they are the same. A key function of the torque converter is to draw the driving member closer to the driven member. As a result of this engagement, the driven member is increased.

>>> Explore how to drive automatic car like a pro:

Right angle gearbox

The make-up of right angle gearbox is based on the arrangement of the output shaft and draft shaft at a 90-degree angle. Subject to the type of gearbox in question, there could be an intersection of the axes in a plane, causing an offset of the axis.

This type of gearbox is formed from a joining of various gear teeth or a joining of various gearing types. Worn and bevel are known to be among the most common gearbox in the single-stage category.

  • Worm gearbox

Worm gearbox has the capacity of producing a self-locking effect as a result of its low efficiency level and high single stage ratios. Having a hollow shaft is also a possibility.

  • Bevel gearbox

You will find several gearing types in bevel gearboxes. You can create bevel gearboxes with intersected axes by forming a synergy between bevel gearing with helical, straight or spiral teeth.

  • Hypoid gearbox

Hypoid gearboxes on the other hand, boast of helical bevel gearing. The axes make use of this to pass with an offset of axis.

It’s possible to combine bevel gearboxes with other forms of gearing. Combining a bevel gearbox with a planetary gearbox is a common practice in this regard. The high degree of radial and axial forces generated by the bevel gear stage is responsible for this. They are deeply rooted via accurate settings.


Can you guess what it is? - A worm gearbox guy!

Advantages of right angle gearboxes

Right angle gearboxes present some advantages for usage. They include:

  1. A clean and compact design.
  2. It can be put to use when there’s limited installation space.
  3. The degree of torque is high when hypoid gearboxes are used.
  4. Combinations with other gearbox types is possible.
  5. Compatibility with hollow shaft

Disadvantages of right angle gearboxes

Just as there are advantages, right angle gearboxes also have disadvantages. They include:

  1. The design is complex.
  2. It has lower efficiency level in comparison to planetary gearbox.
  3. It makes a lot of noise.
  4. It produces lower torque in transmission ratio range

>>> More auto mechanic lessons?

Common gearbox problems

Gearbox related issues constitute the most common problems in cars. First of all, you need to understand that vehicles are mechanical instruments. Hence. They are bound to develop faults. A gearbox has a complex mechanical design. For it to function well, both the small and big parts connected to it must be in good condition.

A number of problems can arise from the gearbox. Some of these problems include:

1. Leakage of transmission fluid

Transmission fluid leakage is inarguably the most common problem that occurs with the gearbox. The transmission fluid is used to oil and lubricate various car parts, so they can move smoothly without friction. It also doubles as the system’s hydraulic fluid. When heat is generated due to friction of the parts, the transmission fluid absorbs it.

The main reason why the transmission fluid leaks is due to damages of the seal. When the seal is broken, the fluid is free to flow out. As the fluid decreases, your vehicle is prone to friction, and this harms the car in many ways.

2. Gear sipping

Gear sipping comes second on the list of most common transmission problems in vehicles.  Such problems include:

  • Delayed response: Normally, a vehicle comes to a stop immediately the accelerator is depressed. But when the gearbox is faulty, even after depressing the accelerator, it takes some time before the command takes effect.
  • Increased RPM: This is simply an unusual rising of the revolutions of the engine every minute.
  • Down-shifting: You’ll notice that your car changes to a lower gear on its own while you are driving on a particular speed.
  • False neutral: Without your command, the car changes to neutral mode.

3. Transmission surging

Transmission surging is a situation whereby the car jerks abnormally when you shift gears. Normally, there’s a segue from one gear to another. But in the face of this challenge, a simple gear change makes your car to jerk. This is as a result of the resistance put up by the car engine.

4. Overheating

Like the human body, a car needs to have good temperature to function well. When your monitor indicates that the vehicle has high temperature, and this isn’t reflected in the radiator, you should check the gearbox immediately. When the fluid cooler lines begin to clog, it’s most likely to overheat.

5. Check engine light

Modern cars enjoy the privilege of having a number of sensors created in them. When the car is at risk of any sort, these sensors pick it up and inform you via their indicators.


The check engine light is an indicator of a faulty gearbox

The check engine light in cars is basically an alarm that gives you a heads-up that your car is in danger. With this tip-off, you are able to swing into action before the condition worsen. But if the check engine light keeps coming on indiscriminately, it loses its essence and should be repaired.


With detailed explanation above, we hope you have fully grasped gearbox definition, how to choose gearbox, types of gearboxes and its common problems in cars. Just some more words before we end the post:

Don’t wait until your gearbox becomes faulty before taking care of it. Carry out car maintenance on all parts of your car to know what’s working and what isn’t working. That way, you are better positioned to avert problems and deal with detected issues before they get out of hands.

And feel free to check out more automobile information right here on Naijauto.com!

Chris Odogwu

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