What is a car transmission?

A car's transmission is a critical part of its mechanical system. It is the system that transfers torque from the engine to the vehicle's driving wheels. The transmission consists of several mechanical parts. There are also different types of transmissions. In this article, we'll take you through the basics of automotive transmissions.

What is a car transmission?

A car transmission is a complex mechanical system that transfers power from the engine to the wheels. In short, a car's transmission is the system that makes the car run! It's made up of several parts:

• Driveshaft: The driveshaft is a long steel or aluminum tube that connects to the wheels at one end and to the car's transmission at the other. It allows the transmission to send torque to the wheels.
• Transmission: A vehicle's transmission transfers power from the engine to the wheels and also facilitates gear changes.  
• Constant Velocity Joints:Constant velocity joints, also known as CV joints, are part of the drive shaft. These joints are designed to bend in any direction, allowing the axle to move with your vehicle while the drive wheels continue to turn. Constant velocity joints are found on front-wheel drive (FWD) vehicles.  
• Differential: Located in the center of the axle, the differential distributes power equally to each drive wheel. Therefore, you will find it in the front axle for FWD, in the rear axle for RWD, and in both axles for AWD.   
• Axle shafts:Located on either side of the differential, the axle shafts transmit power to the drive wheels.

Together, these parts work in harmony to adjust torque and wheel speed according to driving conditions.

However, the transmission of an electric car does not include a gearbox. An electric motor can spin on its own at tens of thousands of revolutions per minute. In addition, it delivers the rotation directly, which is not the case with a conventional internal combustion engine.

Two types of automotive transmissions

Manual transmission

Manual transmissions require driver intervention to change gears using a shift and clutch pedal. It offers direct control over driving and better fuel economy but can be more difficult for novice drivers to master.

Automatic Transmission

Automatic transmissions automatically select gears based on vehicle speed and engine load. It's easier to use but may use slightly more fuel and require more regular maintenance.

How does a car transmission work?

A car's engine provides what's called torque, a mechanical force that turns a system. The engine's torque is applied to an output shaft: this is the drive shaft, also known as a propeller shaft because it is equipped with one or more universal joints. A cardan joint is a type of ball-and-socket joint that transmits rotation between two axes.

This shaft is connected to the differential, which is the part that distributes rotation to the wheels and drive wheels (front, rear, or both on a 4x4). The differential is part of the drive axle. In a 4x4, the car has multiple drive axles.

To make everything work properly, the transmission provides optimal engine rotation and adjusts engine torque to the vehicle's needs. It's the clutch that connects the engine to the transmission. Transmission operation varies depending on the type of transmission:

On a car with a manual transmission, the driver must disengage the clutch to remove torque between the engine and transmission. Traction is momentarily interrupted. The driver then changes gear with the shift lever.

In a car with an automatic transmission, this interruption is not necessary. An electronic control unit takes care of this.

How much does a car transmission cost?

Replacing any part of your car's transmission can be very expensive. However, the price depends on the part and the labor cost, i.e. the length of the intervention.

• To replace a driveshaft, you should expect to pay between $100 and $1,000, including labor, depending on the model of your vehicle. On average, you should expect to pay between $300 and $400.
• Replacing a transmission can cost up to $2,500.