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What Is a Rear Differential?

A view from under a vehicle shows the exposed interior of a rear differential installed between the wheels.

What is a rear differential and what does this key component do? While every vehicle has a differential, whether you have a rear one or not depends on the drive system. Read on for the ins and outs of differentials and how to know which your vehicle has.

What does a differential do?Differential Cover

Have you ever watched a marching band take a corner in a parade? You may have noticed the people on the outside of the turn take longer strides than the people on the inside to keep everyone in line. A differential does the same thing for a car. It compensates for how the inner wheels don’t have to travel as far to get around a corner as the outer ones. The kind of differential that’s installed depends on a few factors.

Front- and rear-wheel drive vehicles

If your vehicle has front-wheel drive, then it uses a front differential that is next to the transmission in a unit called the transaxle. A vehicle with rear-wheel drive has a rear differential that sits between the rear wheels and connects to the transmission through the drive shaft. Both front and rear differentials do the same job — ensuring the wheels move smoothly when you turn the steering wheel — just from different locations.

All- or four-wheel drive vehicles

Things are a bit different with these. An all-wheel-drive vehicle has a third kind of differential called a center differential. It helps distribute power between the front and rear axles since both do the job of steering your car. With four-wheel drive, there is a front and rear differential that’s called a transfer case located in the middle to manage and deliver power to all four wheels. These systems have the same goal as the others: ensuring a smooth turn where the wheels don’t skip or jump.

Signs something is wrong

If your differential isn’t working properly, you may notice several things before it fails altogether. Noticeable tire damage on the sidewall or outer tread of a tire could mean a bad differential. If your car becomes difficult to handle and doesn’t easily steer around corners, that’s another sign that the differential needs to be replaced. The sound of grinding gears or a whining noise are also indicators that you should have your differential checked.

Every car has some kind of differential in order to handle corners with ease. Understanding what a rear differential is and whether or not your vehicle has one isn’t complicated — the only ones that don’t have some kind are those with front-wheel drive. And clues like tire damage, handling, or sounds will let you know when you need to have it looked at.

Check out all the differential parts available on NAPA Online, or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information about how a rear differential works, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Photo courtesy of Flickr.

Nicole Wakelin View All

Nicole Wakelin covers the automotive industry as a freelance journalist for a variety of outlets. Her work includes news pieces, podcasts, radio, written reviews, and video reviews. She can be found in The Boston Globe, CarGurus, BestRide, US News and World Report, and AAA along with lifestyle blogs like Be Car Chic, The Other PTA, and She Buys Cars. She is active on social media with a large following on both Twitter and Instagram and currently serves as Vice President of the New England Motor Press Association.

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