How a Rear differential works in a vehicle? Rear End Differential working principle.

What is Rear Differential Gear?

If a car travels in a straight line, the two rear wheels turn on the road exactly at the same speed. There is no relative movement between the two rear wheels. The propeller shaft may be geared rigidly, in this case, the rear Axle to rotate the rear wheels together.

But when the car takes a turn the outer wheels travel a longer radius than the inner wheel. The outer wheels turn faster than the inner wheel, that is, there is a relative movement between the two rear wheels. If two rear wheels are rigidly fixed to the rear axle the inner wheel will slip, which will cause rapid Tyre wear, steering difficulties, and poor road holding. Therefore there must be some device to provide relative movement to the two rear wheels when the car is taking a turn. The rear differential serves this purpose.

Rear differential
Rear differential


The rear differential is a part of the inner axle housing assembly, which includes the Rear differential, rear axle assembly, wheels, and bearings. The rear differential consists of a system of gears arranged in such a way that connects the propeller shaft with the rear axle. The torque transmitted two each wheel is however equal.

Differential gear, in an automobile mechanics, is a gear arrangement that allows torque from the engine to be transmitted to the driving wheels, dividing the power equally between the two wheels, however, allowing them to follow methods of various lengths, as once turning a corner or traversing an uneven road. On a straight road, the wheels rotate at a similar speed; once turning a corner the outside wheel has farther to travel and can turn quicker than the inner wheel if unrestrained. The first automobile differential was invented in 1827 by a French person, On├ęsiphore Pecqueur. it absolutely was used initially on steam-driven vehicles and was a well-known device once internal-combustion engines appeared at the tip of the 19th century.

Differential Gear
Differential Gear

Rear differential gears

The elements of the Pecqueur differential are shown within the Figure. the facility from the transmission is delivered to the bevel ring gear by the drive-shaft pinion, each of that ar control in bearings (not shown) within the rear-axle housing. The case is AN open boxy structure that’s fast to the ring gear and contains bearings to support one or 2 pairs of diametrically opposite differential bevel pinions. every wheel axle is connected to a differential aspect gear, that meshes with the differential pinions.

 On a straight road the wheels and also the side gears rotate at a similar speed, there’s no relative motion between the differential aspect gears and opinions, and that they all rotate as a single unit with the differential case and ring gear. If the vehicle turns to the left, the right-hand wheel is going to be forced to rotate quicker than the left-hand wheel, and also the aspect gears and also the pinions can rotate relative to at least one another. The ring gear rotates at a speed that’s adequate the mean speed of the left and right wheels. If the wheels are jacked up with the transmission in neutral and one in all the wheels is turned, the other wheel can turn within the other way at a similar speed.


The torsion (turning moment) transmitted to the 2 wheels with the Pecqueur differential is that the same. Consequently, if one wheel slips, as in ice or mud, the torsion to the opposite wheel is reduced. This disadvantage will be overcome somewhat by the utilization of a limited-slip differential. In one version a clutch connects one in all the axles and also the ring gear. once one wheel encounters low traction, its tendency to spin is resisted by the clutch, so providing larger torsion for the opposite wheel.

To understand the working concept of the rear differential, please watch the video below.

Rear End Differential Construction:

Below figure shows the construction of a simple rear differential. The sun gears are mounted on the inner end of each rear axle (called half shaft). A Rear differential cage is assembled on the left axle. A ring gear (called crown gear) is attached to the case, so the cage rotates with the crown gear. The crown gear is driven by the bevel pinion. Both the crown wheel and cage are free on the left rear axle. The cage supports two planet pinions on a shaft which mesh with the two sun gears.

Rear End Differential
Rear End Differential


When the Rear differential cage is rotated, both the sun gears rotate and thus, both wheels turn which is attached to the outer end of the rear axles. Now let us suppose that one wheel is held stationary. Then when the rear differential cage is rotated, the planet gears will also rotate it as they run around on the stationary axle sun gear. While rotating in this manner, the planet pinions carry a rotary motion to the other axle sun gear, causing it, and the wheel too, to rotate. Therefore when one wheel turns more rapidly than the other, while the car is taking a turn, the planet gears spin on its shaft transmitting more rotary motion to one rear wheel than to the other. When both the rear wheels Turn at the same speed the planet pinions do not rotate on the shaft. Thus, when the car is running in a straight line, the Crown wheel, rear differential cage, planet Pinions and the sun gear all turns as a unit without any relative motion. But when the car takes a turn, the planet pinions rotate on their shaft to permit the outer rear wheel to turn more rapidly than the inner Wheel.

How a Differential works?

Rear End Differential

The drive gear a pair of is mounted on the carrier five that supports the planetary bevel gears four that interact the driven bevel gears three attached to the axles one.
The drive shaft enters from the front and also the driven axles run left and right.
In vehicles and different wheeled vehicles, the differential permits the outer drive wheel to rotate quicker than the inner drive wheel throughout a flip. this is often necessary once the vehicle turns, creating the wheel that’s traveling around the outside of the turning curve roll farther and quicker than the opposite. the common of the motility speed of the 2 driving wheels equals the input rotational speed of the drive shaft. arise within the speed of 1 wheel is balanced by a decrease within the speed of the opposite.

Rear differential
Rear differential

Automotive Differential

The drive gear a pair of is mounted on the carrier five that supports the planetary bevel gears four that interact the driven bevel gears three attached to the axles one.
The drive shaft enters from the front and also the driven axles run left and right.In vehicles and different wheeled vehicles, the differential permits the outer drive wheel to rotate quicker than the inner drive wheel throughout a flip. this is often necessary once the vehicle turns, creating the wheel that’s traveling around the outside of the turning curve roll farther and quicker than the opposite. the common of the motility speed of the 2 driving wheels equals the input rotational speed of the drive shaft. arise within the speed of 1 wheel is balanced by a decrease within the speed of the opposite.

Types of Differential

There are mainly six types of differentials used in a vehicle:

  1. Open differential.
  2. Limited-slip Differential
  3. Electronically Controlled Limited-slip Differential. 
  4. Self-locking differential
  5. Torque-vectoring Differential.
  6. Epicyclic differential.

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