8 Signs That You Need a New Rear Differential on Your Car 8 Signs That You Need a New Rear Differential on Your Car

Caring for your car, at times, can feel like caring for a child. There are spills, leaks, and sometimes, a horrifying sound that comes from somewhere you can’t see.

If your car has a rear differential that’s acting up, how do you know? What can do you do to fix a rear differential, and how much effort should you take to repair it before getting a replacement?

We’re going to show you eight signs that your vehicle needs a new rear differential, and how to go about replacing it!

What’s a Rear Differential?

When you’re driving, your car has to be able to compensate for the difference in distance that the inner and outer wheels travel when you’re taking a corner. This is where the differentials come into play. If it weren’t for differentials, your car would turn into a half-finished video game character that doesn’t respond to the player’s controls.

Since the differential is shoved to the back of the car, it usually doesn’t get the same amount of attention as all of the other major components. Oil, brakes, and transmission are usually mentioned in one beat. Ask about the status of your differential at a mechanic and you’re likely to find out if they know what they’re doing.

Most of the time, a four-wheel drive vehicle has two differentials, with a front one added to the rear differential. Each differential powers your engine to give the axles the energy they need to handle turning. 

When Should I Replace a Rear Differential?

​Obviously, you would want to repair a rear differential before replacing it. Not only will it be less labor-intensive, but the cost of repairing it or topping off fluid can be quite drastic compared to an outright replacement.

There are eight signs that you should replace your rear differential, which we’ll look at in the list below. 

#1: Loud Noise

Remember how we compared a faulty car to a noisy child? The same analogy applies to your rear differential. If you begin to hear a sound that resembles howling from the back of your car, that’s not a good sign.

At times, this loud noise will rise and fall in pitch. This can occur when the severity changes how much weight is bearing down on your rear differential.

You need to address this issue as quickly as possible if you can pinpoint the error. It’s a common mistake to think of a faulty rear differential as nothing more than tires hitting the ground. If you let this go, your cost of repair is going to rise very quickly.

#2: Leaky Fluids

If there’s a puddle of anything other than water under your car, it can be cause for concern. A rear differential has its own oil, and many problems start with leaks of this oil. When a leak starts, you can find it at the pinion seal, the axle seals, or the cover of the rear differential itself.

Can you see a light brown, or gray fluid puddling under the back of the car? If this color matches the description, you’ve probably got a rear differential leak on your hands. It’s hard to diagnose the leak without taking it to a mechanic unless you specifically know what to look for. 

#3: Broken Rear Differential Gasket

The cover of the rear differential is commonly made of silicone or rubber. If oil begins to leak out of here, the material will quickly degrade and contribute to the breakdown of the entire differential.

Fortunately, you might be able to fix this with a repair. You can remove the cover of the rear differential and cleaning the sealing surface. After doing this, simply reseal the cover, and that should fix any leakage problems. Barring any complications, you can complete this task in under an hour.

If you choose to repair the gasket, make sure you reapply the cover properly. There’s still a risk of leaking if it isn’t sealed, and the spilled oil will make things worse for the rest of your vehicle. 

#3: Broken Rear Differential Gasket

The cover of the rear differential is commonly made of silicone or rubber. If oil begins to leak out of here, the material will quickly degrade and contribute to the breakdown of the entire differential.

Fortunately, you might be able to fix this with a repair. You can remove the cover of the rear differential and cleaning the sealing surface. After doing this, simply reseal the cover, and that should fix any leakage problems. Barring any complications, you can complete this task in under an hour.

If you choose to repair the gasket, make sure you reapply the cover properly. There’s still a risk of leaking if it isn’t sealed, and the spilled oil will make things worse for the rest of your vehicle.

#4: Leaking Differential Pinion Seal

Check the front end of the rear differential. You’ll find a yoke that physically connects to the driveshaft. If the seal around the pinion has been cut or torn over time, this is where another leak might originate.

While this is still fixable, it’s going to be complicated if it hasn’t been tended to in some time. You have to remove the yoke, pry out the seal, and put on a brand-new seal.

Furthermore, this new seal must be installed without damaging the seal or anything else surrounding it. Be careful if you decide to replace this part, as one small slip can ruin the entire rear differential. 

#5: Worn Differential Side Seals

When these seals are in place, they will stop the rear differential fluid from seeping into your brakes. Running this kind of replacement is also complex. You’ll need to take out the axle shafts completely, and the process of removing and replacing them is among the more labor-intensive tasks involving automotive repair.

While the axles are out, the seals allowing leaks to seep through are replaced. Only when the new ones are in place can the axles be put back together. 

#6: Broken Rear Differential Bearing

You’ll find these bearings on the side of the rear differential, as well as one located on the pinion. That awful screaming sound you’ve been hearing? A bad bearing causes it, and finding a faulty bearing means you have no choice but to replace the entire component.

When you find a bad bearing, you can expect a repair time of up to five hours, and no less than three. 

#7: Worn Rear Differential Gears

The deeper we get in this list, the worse your situation is getting. The teeth on the differential gears can become worn or chipped over time, just like the ones in your mouth.

You won’t find these on the shelf at Walmart – you need to know exactly what you’re doing if you’re going to get your hands dirty enough to fix the gears of a rear differential.

Unfortunately, these are also quite expensive, but it’s still a last resort before a total replacement for a rear differential. 

#8: Replacing the Rear Differential

If none of the steps above will work, you are looking at an outright replacement for your rear differential. If you’re at this stage, there are a lot of components to purchase.

You will need new bearings, seals, and housing. Get your gloves ready if you’re DIYing this project! 

How Much Does Replacing a Rear Differential Cost?

Price of a rear differential

If you can salvage your rear differential by fixing a few small parts inside, it will make a world of difference in your wallet or on the invoice from your mechanic.

Should you find that the bearings or seals can be repaired, you’re looking at a cost of $200 to $400 for the fix. Let’s hope that’s all you need, as the costs are only going up from here.

Once you determine that you need new gears, you’ll be jumping into four digits for repairs. Usually, gears for a rear differential sell for at least $1,500.

Keep in mind that this is just the cost for the part itself and doesn’t factor in the labor for a mechanic to disassemble your entire differential and replace the gear.

Deciding to replace your rear differential may determine whether or not you want to keep your vehicle. Finding a used rear differential and getting it installed could run you $2,000.

If the part is new, you could be paying as much as $4,000. With a number that high, you’ll have to seriously consider how much it will be worth replacing a rear differential. 

How Can I Prevent a Rear Differential from Failing?

Proper care for your car and preventative maintenance doesn’t have to end with oil changes and tire rotations. The rear differential doesn’t get a lot of love because of its location.

When you take your car out, pay close attention to the sounds it makes. Does anything seem off?

Next time you have your vehicle in for service, ask the mechanic to take a look at the rear differential while it’s in the service bay. Just asking about this specific part demonstrates that you have an eye for detail and want the best for your investment.

If you don’t feel like getting on your hands and knees to replace a rear differential, the best thing you can do is monitor the fluid levels. All too often, it’s easy to let little things go unnoticed.

Before you know it, you could have a leak in your rear differential that a simple glance could have prevented.

As you put more miles on your car, the road’s wear and tear will become visible in areas more prominent than the rear differential. Don’t let this potentially expensive replacement out of your sight. Before you find any of these eight signs that you need to replace your rear differential, keep a close eye on your car. It’ll thank you for it!

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