# Everything You Need To Know About Differential

Contents

## Recap

A differential is a type of gear train consisting of three drive shafts, where one shaft’s rotational speed is the average of the speeds of the other two shafts.

Differentials are commonly used in motor vehicles and enable the wheels on each end of a drive axle to rotate at varying speeds, especially when cornering.

Let’s get into more detail!

## What is a Differential?

A differential is a mechanism that transmits an engine’s torque to the wheels for the purpose of splitting the power, allowing the wheels to move at varying speeds. The differential has no effect when the vehicle is moving straight. The effect occurs when the vehicle is trying to make a turn, resulting in the wheel moving at a different speed.

## Functions of Differential in a Vehicle:

The differential has the following three functions on the vehicle’s wheels:

• To help the engine power the wheels
• Transmit the power to the wheels as they rotate at a different speed
• Act as final gear reduction in the vehicle by slowing the rotational speed of the transmission one final time before moving to the wheel
• Another function of the differential is to turn the power flow 90 degrees.

## Major Parts of a Differential System:

The following are the major parts of a differential:

• Pinion Drive Gear: the differential part transfers power from the driveshaft (prop shaft) to the ring gear.
• Ring Gear: the ring gear transfers power to the differential case assembly.
• Spider-Gear: This component lies at the heart of the differential.
• Differential Case Assembly: this part holds the gear and drives the axel.
• Rear Drive Axle: it transfers torque from the differential assembly to the drive wheels.

## Types of Differential:

The different types of differentials include an open differential, a locked differential, a welded or spool differential, a limited slip differential, a Torsen differential, an active differential, and a torque vectoring differential. Visit here to learn more!

## Applications of Differential on a Vehicle:

In a vehicle, the differential is designed to drive a pair of wheels as they are allowed to rotate at different speeds. Vehicles without a differential, such as “karts,” find it difficult to make a suitable turn as both driving wheels are forced to rotate at the same speed.

In this situation, the axle is driven by a simple chain-drive mechanism. When taking a turn with such a vehicle, the inner wheel travels a shorter distance than the outer wheel. This makes the differential useless because either the inner wheel rotates too quickly or the outer wheel rotates too slowly.

However, it results in difficult and unpredictable handling, damaged tires and roads, and stains on the drivetrain. In the application of a differential in rear-wheel-drive automobiles, the propeller shaft helps in the engagement. This is achieved with a hypoid gear (ring and pinion).

The ring gear is mounted on the carrier of the planetary chain that forms the differential. This hybrid gear is a bevel gear that changes the direction of the drive rotation.

## Working Principles of Differential

If a car is making a turn to the right, the main gear may make 10 full rotations. At that time, the left wheel will make more rotations because it needs more travel, and the right wheel will make fewer rotations as it has less distance to travel.

The sun gears, which drive the axle half-shafts, rotate at a different speed related to the ring gear (one faster, one slower). This means 2 full turns each (4 full turns relative to each other), which causes the left wheel to make 12 rotations and the right wheel to make 8 rotations.

The rotation of the ring gear is the average rotation of the side sun gears. This causes the transmission in gear to prevent the ring gear from turning inside the differential when the vehicle is off. In the working of differential, the input torque is applied to the ring gear (blue), which turns the entire carrier (blue).

The carrier is connected to both sun gears only through the planet gear (green). The torque is transmitted to the sun gears through the planet gear. The planet’s gear revolves around the axis of the carrier that drives the sun’s gears.

The planet gear revolves without spinning its own axis if the resistance at both wheels is equal, which turns both wheels at the same rate. However, if the left sun gear (red) experiences resistance, the planet gear (green) spins as well as revolves. Allowing the left sun gear to slow down with an equal speeding up of the right sun gear (yellow).

The following are the advantages of differential:

• It is resistant to EM (electromagnetic) interference as differential signals are transmitted on balanced lines.
• helps in minimizing electronic crosstalk.
• It can be used for high-speed transmission lines with good quality due to noise elimination and less radiation. Hence Common mode rejection as well as improved power supply rejection can be achieved.
• Higher overall signal swings can be achieved.
• It offers the inherent cancellation of even-order harmonics. Some pre-distortion techniques are employed to reduce odd harmonics.