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What is a differential?

First off, what is a differential? You may never have heard of or will ever hear about your differential in your lifespan of car ownership. What you may not realize is that it’s actually an incredibly important part of your car! It is a gear that sits in between the drive wheels of a car that controls the speeds at which they turn. Why would you need your drive wheels to have the speed controlled? Doesn’t that come from the gas pedal? Well, when your car handles a turn, the inside wheel needs to go slower than the outside wheel, because the outside wheel has more ground to cover. The wheels have to turn at different angles and speeds. Fun fact, the angle at which the front wheels need to turn is not the same angle, it is actually adjusted to the center point of a circle that sits on the radius of your back wheels! The differential is the instrument compensates for that “difference” in the physics of your drive wheels.

How does it work?

In most cars, the differential sits in between the drive wheels. If you have a 4-wheel drive, you may have 2 differentials. A differential made of a pinion, a ring gear, spider gears and side gears. The pinion is connected to the drive shaft, which runs down from your steering wheel. The pinion gear turns a ring gear, the ring gear houses the spider gear and two side gears (more side gears for heavier vehicles in some cases). When the vehicle makes a turn, the spider gear turns on an axis to cause one of the side gears to accelerate or decelerate the individual wheels of the car. This describes the basic system of an open differential. There are a few other types of differentials, but this one is inexpensive, lightweight, and doesn’t require a lot of maintenance. The only downside to an open differential there is potential for slip. If your car passes over ice or water and this causes one wheel to slow down, your differential will “think” that because of the lower acceleration, you’re trying to turn! This can cause skidding. An answer to this problem can be found in a limited slip differential, which ensures that power will always be sent to both wheels and only limited power makes it to the wheel that is rotating more slowly, protecting your car from skidding. There is also a type of differential called a locking differential, which locks power to both wheels so that they both receive enough torque to keep rotating. The 4th common type of differential is a torque-vectoring differential, which essentially harnesses the power of sensors and computers to “know” exactly how much torque to give each wheel at all times.

Differential fluid?

As you might imagine, all the gears required to run smoothly against each other could easily be damaged without some kind of lubrication, thus differential fluid, or oil. In some manual transmission cars with front wheel drive, the transmission fluid and the differential fluid can be shared (automatic cars cannot share oil because the manual transmission fluid is a different viscosity, or thickness). If your car has a rear wheel drive, the differential will be housed behind the back wheels. If you have all wheel drive, it is likely that you will have two differentials! The rear differential has its own fluid. Its good to note that when it comes to cars, if there is some kind of fluid or oil, it is likely that there is a way to get it dirty, and it will more than likely need to be changed at some point in the life of the car. Most cars will have the mileage for when it’s time to change the differential fluid in the owner’s manual. You can always give us a call down at 10 th street automotive, and one of our technicians will be happy to answer any questions you might have! You can also schedule an appointment here: