Learn About Automotive Differential

This is a tutorial video of how an automotive differential or the “rear-end” works in your car. Very thorough and easy to understand. This seemingly simple device is the key component to distribute torque to your wheels. There are different types of automotive differentials: spools, locking differentials, limited slip differentials (LSD), and open differential. The list is in order of more locking to less locking.

Types of Automotive Differential


A type of automotive differential called the spools are used almost exclusively in racing/offroad. Spools will not allow torque differentiation, meaning no matter what, both wheels will rotate at the same rate. This can give a great advantage in offroading condition, such as severe duty and racing, and drag racing. By guaranteeing equal distribution of torque to both wheels, you can now see why racers would like to have such device. If it’s so good, why not have it on regular cars, you may ask. Well, if you cannot differentiate the rotation, you are essentially stuck going straight. Only way for you to turn is to have inner wheel slip (chirping tire and burning rubber) because it travels less when making a turn.

Locking differential:

A locking differential is usually heavy duty device that allows you to lock manually. Many have electric switch to engage or disengage the lock. When you lock it, it will act like a spool, the non-differential automotive differential we talked about. This is more common in offroad vehicles, like 4×4 trucks because you can lock at your command when you need the traction.

Limited Slip Differentials (LSD):

An LSD is like an automatic locking differential. These are more common in road race cars and higher end automotive differentials. The operation is simple in concept. The locking portion is really never a full lock but rather, it is operated by friction of some sort like spring and wet clutch, and this allows slippage to prescribed degree when you need to turn and will “lock” when you need the traction. One way to tell if your vehicle has LSD or not, you can jack your car up and rotate the one wheel. If your other wheel rotates in the same direction, then you have an LSD. Another way to test is to perform a burn-out and if both tires lose traction (rubber mark), then you have an LSD, but please do not perform this unless you are completely safe and perform this test at your own risk.

Open differential:

An open differential is the most basic form of automotive differential system as described in the video. This will transmit torque to the easiest path. What I mean is, if one of your wheel is in dirt and another on asphalt and if you try to accelerate quickly, the wheel in the dirt is the only wheel that spins and the wheel on the asphalt remains stationary. Similarly, if you try to burn-out with an open diff, only one wheel will leave the tire mark. This is the most common of all and is the one in your vehicle, unless you drive a sporty car.

Exploded view of an automotive differential http://www.grandmarq.net/gmn/tech/techpics/drivetrain2-4.jpg

I decided to share this information with you because I just changed my 2002 Camaro Z28’s differential oil. Of course, I added Polytron MTC in, the best automotive differential fluid additive, but no more than 6oz since the capacity of my differential is 1.75-2qt. The car runs quieter than before and I feel much more comfortable knowing that my ring-pinion and LSD set will last me for a very long time with Polytron Metal Treatment Concentrate, most advanced oil additive.