Understanding Car Drivetrain System (Explained For Beginners)

Drivetrains are a part of every car and while it may sound like one thing, it’s actually a system that helps power and propels the car.

About Car Drivetrain System

Drivetrains enable cars to move by connecting engines to wheels. Through the transmission, the drivetrain sends power to the drive wheels as the engine runs.

car underneath drivetrain
Car drivetrain system with transmission, driveshaft, and differential

There are different types of drivetrains available:

  • Front-Wheel Drive (FWD)
  • Real-Wheel Drive (RWD)
  • All-Wheel Drive (AWD)
  • 4-Wheel Drive (4WD)

The FWD type drivetrains are the most popular ones you will find in most cars and transmission is simpler as the engine is also in front of the car. Since the back wheels aren’t powered in FWD, there is no driveshaft transmitting engine power there. The transaxle performs this task instead. When a transmission and axle are housed together, it is called a transaxle.

In RWD, driveshafts are connected to transmissions that spin rapidly, transmitting engine power to the rear differentials. The drive is transferred to the rear wheels by the rear differential.

AWD and 4WD use more advanced controls to ensure all wheels receive power, while the basic operation principles apply to all drivetrain types. With all-wheel drivetrains and four-wheel drivetrains, drivers can enjoy a more robust driving experience, even during adverse weather conditions.


Components Of Car Drivetrain System

Identifying problems with your drivetrain will be easier if you understand its components.

These components all work together to function as the drivetrain.


Driveshafts are also called propeller shafts, prop shafts, and drivelines, and are components of the drive train.

Universal joints are connected to the tube’s ends by connectors called yokes.

A joint connects the driveshaft to a stationary part such as the engine or other machine. For the driveshaft to work, several tubes, bearings, and yokes must be combined.

Transmission of power from the engine to the differential takes place via the driveshaft.

As a result, it transmits rotating power from front to back. A vehicle moves by transmitting torque from its transmission to the differential, which is then transmitted to its wheels.

Getting torque from one component to another is essential for driving.

By absorbing movement, the driveshaft keeps two separate parts from breaking while they move.

Your driveshaft will need to be replaced if it breaks, rendering your vehicle undrivable.

There are a variety of shaft configurations for different types of vehicles.

It is important to determine whether your vehicle is front-engine, rear-wheel, or four-wheel drive before ordering the correct part.

If your driveshaft fails, you can have it repaired or you can purchase a new, custom one.


Differentials enable the wheels to rotate at different speeds during turns since they transmit engine power to the wheels.

The forward and rear differentials of your vehicle are more than likely to be part of a four-wheel-drive system. Transmissions work together with differentials to deliver engine power to axles that turn wheels.

The differential drives two wheels at different speeds, allowing them to rotate independently.

As a result of this function, the left and right wheels are driven at proportional speeds.

Driving straight causes the inner tire to rotate at a lower speed than when driving around corners while driving around corners causes the outer tire to rotate at a higher speed.

Your vehicle’s outside wheel needs to travel faster than its inside wheel around a corner, for example.

Torque is equally distributed between both wheels by the differential.

Thus, the wheels can provide traction, or react to resistance, to rotate less by providing more resistance. The faster rotation occurs when there is less resistance on the wheel.

FWD consists of a front-wheel drive differential and a transmission encased in a housing called a transmission housing.

With rear-wheel drive (RWD), the differential is attached to the transmission via a driveshaft between the rear wheels.

It is possible to have “electronic” AWD on some hybrid vehicles. The rear wheels on these vehicles are driven by electric motors, which enable them to turn faster or slower around corners as needed.

Basically, a differential connects an engine to its wheels by transferring torque. In order to allow the wheels to spin at different speeds, the differential divides the power from the engine.

Each wheel can turn independently of the other, so rotating it around a corner won’t be an issue.

Modern differentials look incredibly complex when viewed from the front.

Universal Joint

There is a wide range of mechanical applications for universal joints or UJs.

Two shafts that are not in line with one another, use this type of joint to transmit torque and power.

In the absence of an intermediate connection point, UJs are a great alternative to yokes.

The components and functions of universal joints will be discussed in more detail.

Two yokes and four trunnions make up universal joints.

Angular misalignments are possible between shafts connected by the UJ due to these components.

It is possible to move the joint smoothly when the yokes are engaged by inserting needle bearings into the trunnions.

As well as keeping out dirt and moisture, UJs are fitted with dust boots to extend their life.

In spite of the fact that two shafts may not be perfectly aligned, universal joints allow them to be linked together.

There is no additional transmission loss or vibration issues associated with angular misalignments up to 5 degrees. 

The power transmission efficiency and effectiveness of these devices make them ideal for applications where space constraints make it impossible to use an intermediate connection point or where multiple angles must be connected for efficient and effective power transmission.

An angle-connected universal joint is also referred to as a U-joint. In addition to transmitting power between shafts, it allows shafts to rotate at different speeds and angles.

Industrial machinery, power tools, and other equipment utilize universal joints in conjunction with driveshafts to connect the driveshafts to the transmissions.

CV Joints

CV joints ensure a constant rotational speed and variable angle power transmission without increasing friction or play when transferring power. Vehicles with front-wheel drive are most likely to use these joints.

In the event of a damaged CV joint, driving can be dangerous. Whenever the boot is damaged, the grease sealing the CV joint leaks.

Contamination will build up and eventually result in joint failure. The car could become undrivable if the CV joint is badly worn.

As the name suggests, constant velocity joints, or CV joints, are the components of a vehicle that assist in transmitting power at a constant speed and through changing angles with little friction.

Each front-wheel car has constant velocity joints at the ends of its shafts. There are several CV joints inside the vehicle, which are connected to different shafts and transmissions.

CV joints are found in all kinds of vehicles, including trucks, car rear-wheel drives, and four-wheel drives.  CV joints maintain the suspension’s up-and-down movement by moving acceleration to the wheels.

When turning, torque is received by front-wheel-drive cars through CV joints.

Axle Shafts

Transmissions and wheels are connected by drive axles in a vehicle’s drivetrain.

To move the vehicle, axle shafts transfer rotational force and power from the transmission.

Whenever the axle shaft rotates due to the force from the transmission, the connected wheels also rotate. Located between two half axles is a universal joint (UV) that separates the axle shaft into two halves.

In the end, axle shafts facilitate wheel movement and allow vehicles to roll. There would be no movement on the wheels of a vehicle without reliable drive shafts.

Vehicle types require different axle shafts, which handle different types of stresses. In addition to the axle shaft length, how the vehicle attaches to the axle shaft depends on the hubs and bearings of the vehicle.

There are three main types of axle shafts:

1. Semi-Floating Axle Shafts

An axle shaft with flange faces is designed in this manner. The associated wheels are attached directly to these faces.

2. Fully Floating Axle Shafts

This axle shaft style has hubs between the axle shaft and the wheels, rather than flange faces that connect the axle shaft directly to the wheels. Wheels are connected to hubs, and those hubs rotate on roller bearings attached to spindles at both ends of the axle shaft.

In addition, the hubs and bearings handle the axle’s weight to reduce stress on the axle bearing. The roller bearings are tapered and face opposing directions. As a result, the axle bearing only has to withstand the torque generated by the transmission system, rather than supporting the weight of the vehicle and its cargo.

3. Three-Quarter Floating Axle Shafts

Semi-floating and fully floating axle shafts are incorporated into these axle shafts. Bearings are positioned between the hub axle shaft and axle casing in three-quarter floating axle shafts. Shearing or bending forces are, however, not applied to the bearings.


In your car, the transmission plays a crucial role. The transmission transfers engine power to the wheels. Cars cannot move without transmissions.

A manual transmission and an automatic transmission are the two main types of transmissions.

Manual transmissions typically have five or six forward gears and a reverse gear, which the driver shifts manually. The torque converter in automatic transmissions helps the driver change gears seamlessly without adjusting anything manually.

Some newer models of vehicles have ten or more gears, although automatic transmissions generally have four or five gears.

Before choosing which type of transmission is right for you, make sure you research both types’ benefits and drawbacks. It is essential to understand what transmissions do and how they work regardless of whether you are buying a new car or replacing your current one.

Power is produced by rotational energy in the engine. By converting rotational energy into linear motion, the transmission transfers that energy to the wheels. The transmission must be capable of changing gears in order to do this. The gears used by the vehicle will vary based on the vehicle’s speed and the load it is carrying.

Transmissions change gears by means of gears. Gearboxes contain these components. Various gear ratios are contained in the gearbox.

Ratios correspond to different combinations of speed and load. By selecting the appropriate gear ratio, the transmission changes gears when needed.

In order to change gears, a clutch is used. Transmissions are disengaged from engines through clutches. It is necessary to disengage the engine before changing gears, as the transmission requires it.

During transmission gear changes, the clutch maintains engine position through friction. Automatic transmissions use torque converters to disconnect the engine from the gearbox.

Power is again transferred to the engine once the clutch has been released and the new gear ratio selected. Unless you shift an auto transmission on your own or operate a manual transmission, the entire process happens quickly and smoothly.

Final Thoughts

The drivetrain system might seem complicated but if you think about each component and how they work together in the system, it will help you understand how your vehicle operates and could help you identify problems within the system.