What is A Differential In A Car: Types, Parts, Functions & How Does It Work?

Often, when a car or truck turns in any direction, the speed of the drive wheels of that vehicle becomes unequal to each other, and when the vehicle moves straight, then the speed of the drive wheels on both sides becomes the same. Have you ever tried to know why this happens and how it is possible?

This happens because differentials are used in cars. A differential is a mechanical device that makes the speed of the drive wheels unequal when the vehicle turns in any direction and equalizes the speed of the wheels on both sides when the vehicle moves straight.


Let us learn in detail about differentials in automobiles so that you can know in depth about their function, types, and working.

What Is A Differential In A Car?

A differential in vehicles is a mechanical gear set that allows the drive wheels to rotate at different speeds as the vehicle turns, and the vehicle is able to turn smoothly in any direction without friction and traction.

A differential consists of a set of gears housed within the axle, including the drive shaft, solid shaft, ring gear, pinion gear, spider gear, differential cage, and side gears mounted in the differential, which transmit motion from the axle to the axle. Are. drive wheels.

When a vehicle turns, the differential reduces the speed of the inside wheel and automatically increases the speed of the outside wheel as the vehicle turns. The differential is an essential part of the efficient operation of a vehicle, whether it is front-wheel drive, rear-wheel drive, or all-wheel drive.

How Does A Differential Work?

Differential is a type of mechanism. The differential controls and manages the rotational speed of the vehicle’s drive wheels when a vehicle is moving in a straight direction.

But when the vehicle is turned in any direction, the differential slows down the speed of the drive wheel inside the vehicle in the direction of turn and accelerates the speed of the drive wheel on the outside site.

Hence, there is a difference in the speed of both the wheels while turning. Because if the speed of one wheel is not reduced while turning, the vehicle turns with friction and traction. But when the vehicle is moving straight, the speed of the drive wheels becomes the same.

Types of Differential In Automobiles

Commonly, four types of differential systems are used in vehicles.

1. Open Differential

Usually, this type of differential is used in cars meant for personal use. This type of differential is used in cars in which engine torque is transmitted to the rear wheel by the propeller shaft.

In those cars, the drive is fitted in the center of the wheels and the front drive wheels are fitted in the transmission gearbox by shortening this, which changes the speed of the drive wheels when the car takes a turn.

2. Locking Differential

This type of differential is used for trucks, tractors and heavy vehicles. In which rotation power is added to the drive wheels through differential lock according to the need and situation. so that both the drive wheels can achieve the same speed. And according to the need, both the wheels can exert equal thrust. This differential has a separate lever for the lock on the outside. which can be used as per the requirement and this lock can be opened when not needed.

3. Limited Slip Differential

This type of differential is used in sports cars when one of the drive wheels loses traction while taking turns. This locking differential is then transferred automatically. This allows the wheels to have more control and traction with the road surface. A limited-slip differential also works on the mechanism of an open differential.

4. Torque-Vectoring Differential

This type of differential is used in trains, which fine-tunes the engine torque delivered to each wheel, causing each wheel to rotate and adjust the speed as required.

Parts Of Differential

In fact, the differential used in vehicles is a complex mechanical component consisting of several important parts that work together to operate efficiently and allow the wheels to rotate at different speeds.

The main parts of the automotive differential are as follows:

Ring Gear or Crown Gear

The ring gear in any automobile differential is a large gear attached to the differential case. It is also called the crown gear. The ring gear receives the engine power from the driveshaft and transmits it to the pinion gear, and then the pinion gear starts working.

Pinion Gear or Crown Pinion

The pinion gear in a differential is a small gear attached to the driveshaft, also known as a crown pinion, which mates with the ring gear and transfers engine power from the driveshaft to the differential case.

Differential Case

The differential case contains the differential gears, and these gears are mounted within the axle housing. These gears provide power to the axle shaft and allow the vehicle’s drive wheels to rotate at different speeds. Irrespective of whether the vehicle is taking a turn or moving straight.

Differential Gears

Inside the differential case, there are several gears. These gears play a vital role in the functioning of the differential, transmitting power from the ring gear to the axle shaft. These gears allow the wheels to rotate at different speeds while maintaining uniform torque distribution.

Axle/Half Shaft

Axle shafts connect the differential to the drive wheels. The axle shafts transfer power from the differential to the wheels, allowing them to rotate and propel the vehicle.

Bearings and Bushings

Bearings and bushings are used for the rotating components of the differential, which reduce friction and ensure smooth operation. Bearings, or bushings are used at the ends of the differential assembly.

Side Gear & Spider Gear

The side gears in the differential are connected to the axle shaft and mesh with spider gears inside the differential case. Spider gears allow the wheels to rotate at different speeds during a turn while transferring power evenly between the axle shafts.

Differential Housing

The differential housing is an outer covering that covers the differential assembly. It provides protection to the internal components and is filled with differential fluid, which helps maintain proper lubrication.

Symptoms Of A Bad Differential

A differential is a mechanical gear system and wear and tear over time is a natural process. Therefore, the symptoms and signs of a bad or worn differential should be paid attention to, so that you can get it repaired in time and avoid any major damage.

  • Driveline noise and vibration
  • Screeching sound under the vehicle
  • Strange noises when turning the vehicle
  • Whispering Sound
  • Oil leakage from the differential area
  • Vehicle turning problem
  • Feeling of vibration in the cabin 
  • Jerking on slow or high acceleration

What Is Differential Lock?

A differential lock is an important mechanism of a differential unit, also known as a diff lock. The differential lock simultaneously locks the rotation of the vehicle’s left and right wheels on the same axle, allowing the right and left drive wheels to rotate at the same speed.

The differential lock is particularly useful in tractors, trucks, and other off-road vehicles and is especially used in mud, snow, or steep slopes. The main function of the differential lock is to force both wheels to rotate simultaneously on the same axis, so that the right and left drive wheels rotate at the same speed, even if one wheel has less traction than the other.

However, any technology also has some advantages and disadvantages. Similarly, differential locks can also have some disadvantages. As in many cases, the differential lock becomes stuck and can cause damage to the drive train or internal components of the differential.

What Happens if The Differential Fluid Level is Low?

Many small and big gears are fitted in the differential, and these gears play an important role in its functioning. These gears require lubrication to reduce excess friction, which is accomplished by the differential fluid.

But if the differential fluid level is low, a lack of lubrication may cause differential overheating, abnormal noise, or damage to internal parts. That’s why you should regularly check your vehicle’s differential fluid levels and leaks.

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