Almost all cars, trucks, and SUVs have a differential. We tackle everything from what a differential is to what types of differentials there are.
Among all of the integral parts of a working automobile, the differential or differentials are some of the most important. Without them, cars wouldn’t be as smooth, comfortable, and capable as they are today. The differential dates back to 1827 and over the years it’s become far more sophisticated and capable. Today, we’re going to break down what a differential is, how it works, what the major types are, and whether or not all cars even have one.
A differential is a mechanical part that transmits power to the wheels and allows the wheels to rotate at different speeds. When you make a turn, the inside wheel (left for left turns, right for right turns) needs to travel at a slower speed than the outside wheel. If it can’t, one wheel will stutter because it’s forced to maintain the same speed as the other wheel. A differential allows for different wheel speeds while maintaining drive power to at least one wheel (most often the outer wheel).
It does so through a gear or pair of gears that connect to each drive axle. When the vehicle makes a turn and the wheels need to travel at different speeds around that turn, the differential continues to provide power to one wheel while allowing the other wheel to travel at a different speed.
Non-drive wheels, like the front wheels in a rear-wheel drive car, don’t need a differential of any kind since they’re not connected to one another in any way. For more information on which wheels are your drive wheels see our article on powertrains explained.
Most automobiles feature one of four different types of differential. The most common is the open differential which sends the bulk of engine power and torque to the wheel with the least resistance. If you’ve ever seen a car do a burnout and leave just one rubber tire mark, you’ve witnessed how an open differential works. Since that one wheel was already spinning, all of the available power and torque was sent there and not to the other wheel.
A locking differential, similar to the ones found on many 4WD vehicles, provides completely equal power to both sides of the axle. While this does make turning much harder, it aids in low-speed traction and can often help get stuck vehicles unstuck or out of low-grip situations like the ones often encountered off-road.
Many modern vehicles use electronically locking differentials for exactly this reason. When the driver needs to lock the differential to get through a sticky situation, they can do so from the cabin and then unlock the differential once back on solid ground.
A limited-slip differential typically acts much like an open differential until wheel slip occurs. At that moment, the differential feeds power back to the non-slipping wheel. Typically, it does so through a series of clutch packs but other methods can be used to produce the same result as well.
Finally, a torque-vectoring differential utilizes planetary gear sets, clutch packs, and or electric motors to control exactly how much torque is provided to each wheel. The result is that a car with a torque vectoring differential can corner more quickly since power is sent to the most effective wheel throughout the phases of a turn. It can also improve stability both on entry and exit of corners but also while traveling straight down road surfaces that don’t offer optimal grip.
No, not all cars have a differential but that’s a relatively new development. Those cars are all-electric ones. Cars like the Rivian R1T pickup or the R1S SUV use individual motors at each wheel so they don’t have any physical connection between the wheels. Thus, there’s no need for a differential.
Not all electric cars are devoid of differentials. Tesla, for example, uses open differentials in many of its vehicles.
Without differentials, most vehicles would be a lot rougher to drive than they are. Thankfully, this component smooths out the ride, provides better traction at times, and improves comfort for all of us. For more information on how modern suspension components do the same, see this article.