You get your engine oil changed every few thousand kilometres but have you ever thought about your differential?
The differential is a component in all cars and is designed to compensate for the difference in distance and the varying speeds between the inner wheels and outer wheels as the car goes around a corner.
Changing the differential oil is one of the most overlooked vehicle maintenance tasks. We recommend you ask your transmission specialist to check it regularly as it gets none of the star treatment that the engine does. The reason for this recommendation is that if lubrication in the differential fails, you won’t be getting very far for very long.
The differential has three jobs:
- To allot engine power to the wheels.
- To act as the final gear reduction in the vehicle, slowing the rotational speed of the transmission one final time before it hits the wheels.
- To transmit the power to the wheels while allowing them to rotate at different speeds (this is what gave “differential” its name and this transfer of power of often referred to as ‘differential action’).
Why you Need a Differential
Car wheels spin at different speeds, especially when turning. If all wheels were travelling at the same speed while turning, the vehicle would experience a great deal of “stuttering”. Each wheel travels a different distance through the turn, and the inside wheels travel a shorter distance than the outside wheels. Since speed is equal to the distance travelled divided by the time it takes to go that distance, the wheels that travel a shorter distance travel at a lower speed. Also note that the front wheels travel at a different distance than the rear wheels.
For the non-driven wheels on your car (the front wheels on a rear-wheel drive car, the back wheels on a front-wheel drive car) this is not an issue as there is no connection between them so they spin independently.
However, the driven wheels are linked together so that a single engine and transmission can turn both wheels. If your car did not have a differential, the wheels would have to be locked together, forced to spin at the same speed, this would make turning difficult and hard on your car. For the car to be able to turn, one tyre would have to slip and with modern tyres and concrete roads, a great deal of force is required to make a tyre slip resulting in a heavy strain on the axle components. This is due to the force is being transmitted through the axle from one wheel to another.
The differential is a device that splits the engine torque two ways, allowing each output to spin at a different speed. The differential is found on all modern cars and trucks, and also in many all-wheel-drive (full-time four- wheel-drive) vehicles. These all-wheel-drive vehicles need a differential between each set of drive wheels, and they need one between the front and the back wheels as well, because the front wheels travel a different distance through a turn than the rear wheels. Part-time four-wheel-drive systems don’t have a differential between the front and rear wheels; instead, they are locked together so that the front and rear wheels have to turn at the same average speed. This is why these vehicles are hard to turn on concrete when the four-wheel- drive system is engaged.
The differential needs to be serviced like any other component of your vehicle. Dirty differential fluid could contain particles of metal, which would indicate excessive wear of internal gears and potential problems. Fortunately, you only need to change this oil every 50,000 to 80,000 kilometres.