5 Symptoms Of A Bad Differential & Replacement Cost

Your car’s differential is one of the key players in keeping the car moving in the right direction. It’s essentially what keeps your front and wheel tires on the same page, making sure each set is given the right amount of power to go in whichever direction the driver wishes. When your differential goes bad, it could be bad news for your car.

We’re going to take a look at bad differential symptoms to look out for and what causes a rear differential to go bad in the first place. Hopefully, this knowledge will help you keep your car differentials in working order and alert you when you need to take it in for service.

What Causes a Rear Differential to Go Bad?

Let’s start with getting to the root of the problem. What causes a rear differential to go bad?

Well, one of the main reasons a differential goes bad, is the way in which one drives their new car. There’s a grace period where your car has to be ‘broken in’ and putting too much stress on your engine too soon can cause some front or rear differential noises that signify a larger issue.

By putting too much stress on the new car, we mean driving too fast (more than 50 mph) for long periods of time or by towing or hauling another object, such as an RV or a boat. This can cause your differential to overheat and start to break down.

The easiest way to cause problems with your differential is to allow your car to spin out a lot. Every once in a while, unintentionally, spinning out shouldn’t cause too much harm.

But instances, where your front wheels remain on the road while your back wheels slide out, will cause harm. It’s these kinds of driving maneuvers that could crack or damage parts of your differential.

Symptoms Of A Bad Differential

Five Symptoms of a Bad Rear Differential

Damage To the Tire

If you find sidewall or outer tire wear on the rear wheels, it’s a good indication that your differential might be failing. The differential allows the tires to spin at different rates during cornering, and when it fails, the gears grind, causing the tires to turn at the same rate, which wears out the tires.

Reduced Handling Capabilities

With a bad differential, handling around corners can become unpredictable, and it’s noticeable that the vehicle isn’t functioning as expected.


A bad differential can cause vibrations that increase in intensity as you speed up and reduce as you slow down. If you have this issue, avoid driving at high speeds and bring your vehicle into a shop as soon as possible.

Grinding Gears

Grinding gears is another significant sign that your differential is failing and that the gears are wearing themselves out. In this situation, you will want to avoid driving the vehicle as it can lock up the rear wheels at any moment, which is dangerous.

Whining Noises

Hearing whining noises can indicate that your differential is failing, but this is not a guarantee since it is also a symptom of a bad wheel bearing.

What Are the Repair Options for A Rear Diff?

Gasket Replacement

Most rear-diff covers are rubber or silicone, which can wear and dry out over time. To prevent them from leaking, you’ll have to have them replaced. Thankfully, this is an easy repair that shouldn’t take more than an hour.

Bearing Replacement

There are two bearings in a differential, the one for the pinion, and the one for the side.

Once it begins to grind or hum, you’ll have to have one or both of them replaced. Since this requires dismantling the diff, it can take as much as 5-hours to complete, meaning it’s a lot more costly to do so.

Sealing The Piston and Side

If you do notice a puddle of fluid under your car, it may mean that the piston or the side needs to be sealed. Both require a lot of time to repair, especially the latter – since the axle shafts have to be removed as well.

Replacing The Rear Differential Entirely

If none of the above repairs are possible, you may have to have your rear diff replaced entirely.

This is the worst-case scenario, which usually means the gears in the diff are unusable.

Differential Replacement Cost

The average replacement cost for a whole rear differential is between $1000 and $4000. Luckily, you can just repair it or replace it with a used differential, which will decrease the costs a lot.

Most differential repairs will cost between $200 and $400 to repair. Of course, this depends on the severity of the defect and what parts need to be replaced.

For a rebuilt differential, you might need to spend between $400 and $1,000. On the other hand, replacing a differential cost $1,000 to $2,000 on average.  This isn’t a job that most people will tackle on their own but will require the help of a trained technician.

How Do You Maintain A Rear Differential?

The best thing you can do to preserve the life of your rear diff is to change the differential fluid every 30,000-50,000 miles. Additionally, you should have your drivetrain inspected annually.

Doing so will ensure that any repairs are simple, rather than needing a full differential replacement.