What is the gearbox inside the engine?

When it comes to the inner workings of a car's engine, the gearbox is often overlooked, but it plays a crucial role in the overall performance and efficiency of the vehicle. The gearbox, also known as the transmission, is the component that transfers the power generated by the engine to the wheels, allowing the car to accelerate, maintain speed, and change direction.

What is a Gearbox?

A gearbox is a mechanical device that consists of a series of gears and shafts that work together to transmit the rotational force from the engine to the wheels. It is responsible for converting the high-speed, low-torque output of the engine into a lower-speed, higher-torque output that is more suitable for driving the wheels. This allows the engine to operate at its most efficient speed while still providing the necessary power to the wheels.

How Does a Gearbox Work?

The gearbox works by using a set of gears that can be engaged or disengaged to change the gear ratio, which is the relationship between the speed of the engine and the speed of the wheels. When the driver shifts gears, they are selecting a different gear ratio that is better suited for the current driving conditions, such as accelerating, cruising, or climbing a hill.

The gearbox typically contains the following components:

• Input shaft: Connects to the engine and receives the rotational force


• Output shaft: Connects to the wheels and transmits the rotational force


• Gears: Vary in size and number of teeth to change the gear ratio


• Synchronizers: Ensure smooth gear changes by matching the speed of the input and output shafts


• Clutch: Disengages the engine from the gearbox to allow for gear changes

The gearbox is a crucial component of a car's powertrain, as it allows the engine to operate at its most efficient speed while still providing the necessary power to the wheels. Without a properly functioning gearbox, a car would be unable to accelerate, maintain speed, or change direction effectively.

Types of Gearboxes

There are several different types of gearboxes used in modern vehicles, each with its own advantages and disadvantages:

• Manual Transmission: Requires the driver to manually shift gears using a clutch pedal and gear shift lever.


• Automatic Transmission: Shifts gears automatically based on the vehicle's speed and engine load, without the need for driver input.


• Continuously Variable Transmission (CVT): Uses a system of pulleys and belts to provide an infinite number of gear ratios, rather than a fixed set of gears.


• Dual-Clutch Transmission (DCT): Combines the efficiency of a manual transmission with the convenience of an automatic, using two clutches to provide seamless gear changes.

Each type of gearbox has its own strengths and weaknesses, and the choice of transmission often depends on the intended use of the vehicle, the driver's preferences, and the overall design of the powertrain.

What is a gearbox in a motor?

A Gear Box is often called a transmission. Gear boxes simply refer to a set of gears and their casing, most commonly found in automobiles. Since most motor vehicle engines have high operating and idling speeds, transmissions allow the machinery to operate efficiently and even aid in slowing and shutting down machinery.

Is the gearbox inside the engine?

A gearbox, also known as transmission, is a mechanical component that helps to transfer power from the engine to the wheels by using different gear ratios. It is usually located between the engine and the wheels, consisting of several gears, shafts and bearings.

What happens if the gearbox is damaged?

When a car's gearbox fails, the vehicle will likely lose the ability to move, or experience severe performance issues like sudden power loss, loss of traction, and engine stalling or surging. In an automatic, the transmission might slip into neutral, while in a manual, it could get stuck in one gear or refuse to shift at all. This can make the car difficult or impossible to control, and if it happens while driving, it can create a dangerous situation. 
What happens during a gearbox failure

• Loss of power: The engine will run, but the transmission will be unable to transfer its rotation to the wheels, so the car won't move. 
• Gear slippage: The car may unexpectedly shift out of gear or into neutral, especially in an automatic transmission. 
• Stuck in gear: The transmission may get stuck in a specific gear, preventing you from shifting up or down. 
• Engine stalling or surging: The engine may stall or surge, particularly when you attempt to shift gears. 
• Sudden stopping: In the worst-case scenario, the transmission may lock up, cause a horrible grinding noise, and bring the vehicle to an immediate and sudden stop. 

This video explains how to identify the warning signs of a failing transmission: 59sCar GuideYouTube · Oct 12, 2025
What to do if your gearbox fails

• Safely pull over: Turn on your hazard lights and pull over to the side of the road as soon as it is safe to do so. 
• Park the car: Once stopped, put the car in park. 
• Call for a tow truck: Do not attempt to drive the car further. Call a professional towing service to take your vehicle to a repair shop. 
• Consider repair costs: Before you get the work done, it's wise to get an estimate. The cost to replace a gearbox can be significant, so it's worth weighing this against the value of the car. 

How much does it cost to replace a gearbox in a car?

If you're in need of a gearbox replacement, it could set you back anywhere between $3000-$12000+ depending on your car.