The differential was first invented in China, in the third century,A.D. After turning a car the outside wheel has to turn faster then the inside one in order to cover the greater distance. That is why two wheels are not driven at a same speed. So we need a differential gear. A car differential is a place halfway between the wheels, on either the front or both axes.

Main mechanisms:
Wheels receive power from the motor via drive shaft. The power receiving wheels which makes the vehicle move fowrord are called as the drive wheels. Wheels receive power from the motor via drive shaft.
The main function of the differential gear is to allow the drive wheels to turn at different Rpm while from the engine. The main characterics of differential is to, * To aim the engine power at wheels. * To transmit the power to the wheels while allowing them to rotate at differential speeds.

the left wheel has to travel more distance compared to the right wheel. If the wheels where connected using a soil shaft. The wheels where connected using a soil shaft. The wheels would have to slip to accomplish the turn. The mechanism in a differential allows left and right wheels to turn at different Rpm, while transferring power to both the wheels.
Differential parts:
There are three types of gear available,
Pinion drive gear:
Transfers power from the drive shaft to the ring gear.
Ring gear:
Transfers power to the differential case assembly
Side/Spider gears:
Helps both wheels to turn independently while turning.
Differential case assembly:
Holds the ring gear and other components that drive the real axle.
Power flow:
First drive shaft spins the pinion gear. Pinion gear turns the larger ring gear. Ring gear attached to differential case. Hence it rotates with ring gear. Then differential case spins the sun gears which attached to the axles. Axles transfer power to the wheels.

Function: * Transfer power from drive shaft to the wheels * Provides final gear reduction * Splits amount of torque going to each wheels * Allow the wheels to rotate at different speeds in turns
Hypoid gears:
Most of the modern differentials have hypoid gears. Pinion gear sits offset, lowred from the ring gear. It has more contact area compared to the other gear pairs and will make sure that the operating gear is smooth.
It’s advantage is to improve gear life and reduces gear noise.
Other functions of differential gear:
Apart from allowing the wheels to rotate at different Rpm differential has two more function. First is
Speed reduction:
This is achieved by using ring gear which having at most 4-5 times number of teeth as a pinion gear.Such huge ratio will bring down the speed of the ring gear. Such huge gear ratio will bring down the speed of the ring gear. Science the power flow at the pinion and ring gear are the same, such a speed reduction will result in a high torque multiplication.
The other function of the differential is to turn the power direction by 90 degree.
Differential problems: Bearings: (humming sound gets louder with higher speeds)
Solutions:
* Lift the vehicle on the hoist. * Put it in gear and spin the wheels at approx. 50 Km/hr. * Use a stethoscope to listen for a humming sound by the carrier bearings and the pinion bearings.
Ring and Pinion problems: * If backlash between ring gear and pinion gear is too great, a clunking sound can be produced, especially when an automatic transmission is shifted into gear. * Lack of service or low fluid can cause this problem. * Will show up as whining or howling noise that changes when going from acceleration to deceleration.
Also there is a situation where one wheel of the vehicle is on the surface with good traction and other wheel in the slippery track. In this case a standard differential will send the majority to the slippery wheel.