There are valuable parts of your car that you don’t realize exist—until something goes wrong. Your rear differential is one of those parts, and trust us, when this part goes bad you’ll never forget about it again.
If your car makes a whining noise each time you turn a corner or a whirring sound compounded by noticeable vibrations on the highway, it could be your car letting you know that your rear differential is going bad.
Differential repairs and replacements can become costly if you don’t maintain them accordingly. Now that you know this part exists, it’s time to learn more about what it does, how to maintain it, and what your options are if something goes wrong.
Keep reading to learn more.
Rear Differential 101
You’re probably wondering, what does a rear differential do exactly? In short, your rear differential allows for a pair of tires to move in the same direction while rotating at different speeds.
Without getting too much into the physics, the differential distributes an equal amount of torque to each wheel which enables them to react to any resistance provided by the differential while also providing traction. By using resistance, the differential can control the speed of each tire individually.
For example, when you turn a corner, your exterior wheel has to move faster than the interior wheel. Your differentials handle this.
Your differentials can be part of your front or rear axle assembly—or both—depending on the type of vehicle you drive. For example, if you have an SUV with 4-wheel drive, then you have both a front and rear differential. There are actually three different types of differentials:
- The Open Differential is the most commonly used for a variety of vehicle types. However, it does not control slippage, making it a flawed design for off-road vehicles and hot rods.
- The Limited-Slip Differential is very similar to the first type, however, it’s designed with an integrated clutch system. This system allows the left and right axles to lock when traction is lost, making it a great design for sport utility vehicles and other high-performance vehicles.
- The Torque-Vectoring Differential is the latest in differential parts and technology. Using sensors that read the steering system, engine components, and road surface, these differentials adjust themselves accordingly. This increases vehicle performance as well as traction and safety.
Regardless of the type of differential—or differentials—that your vehicle is equipped with, these unsung heroes sitting at the end of your drivetrain need your attention from time to time.
Symptoms of a Bad Rear Differential
Like we said, your differentials need your attention from time to time. A differential is made up of internal gears and bearings covered in a specific oil to keep them lubricated and to keep them from overheating. This oil prevents wear and damage to the internal gears—the ring and pinion gears.
Over time, that oil breaks down and those metal gears begin to chip as do the bearings. The metal that chips off remains in the broken-down oil, which is why every so often you’re supposed to take your vehicle in for a differential fluid change. If you haven’t don’t get the oil changed, you run the risk of permanent damage not just to your differentials—but your transmission as well.
If your rear differential has gone bad, you may notice some of the following symptoms:
- A whirring noise upon deceleration
- A whining noise or howling when accelerating
- A rumbling or whirring at speeds over 20 MPH that change when turning
- A clunking noise when you first begin to move your car
- A steady vibration that increases with speed
You also want to keep a lookout for a leak, which typically happens at the axle seals or pinion seal. If your rear differential is leaking, it’ll be pretty easy to spot since it will be towards the back of your vehicle. If you do spot a leak, then your level of stress should be directly related to the size of said leak—the larger the leak, the more worried you should be.
Your engine’s power is transferred to your wheels through your rear differential. If it goes out while you’re driving, you’ll experience anything from loss of power to loss of control. If this happens to you, you must pull over immediately.
Types of Rear Differential Repairs
There’s no “one-stop-shop” for repairing your differentials. There are quite a few different types of repairs that can be carried out since your differentials have such intricate components. The costs will reflect the parts that need to be replaced and the hours of labor involved, not to mention diagnostics.
Starting with oil leaks, repairs may include:
- Gasket Replacement. Differentials have a rubber or silicone seal inside the cover that deteriorates over time, causing the oil to leak. This repair requires the cover to be removed, cleaned, and the new gasket to be put in place and sealed.
- Pinion Seal Replacement. This repair is more in-depth because it requires the yoke that sits in front of the driveshaft to be removed. The pinion seal sits around the yoke and wears down over time. Once the new seal is put in it has to be carefully driven into place.
- Side Seal Replacement. There are two side seals that prevent the differential oil from leaking onto your breaks. For this repair, the entire axle assembly has to be completely removed so that the worn-out seals can be replaced.
The non-leak repairs may include:
- Bearing Replacement. There are side bearings and a pinion bearing which also deteriorate over time. This is what causes the whirring noises and vibrations you may hear. Bearing replacement on your rear differentials can take up to five hours and require special tools to push them in and out.
- Gear Replacement. Chipped and worn down teeth on your differential gears also cause the noises you hear when these parts go bad. These are integral parts of your differentials and can cost up to $1,500 between the new parts and the labor.
- Complete Replacement. When the gears are beyond saving, it’s time for an overhaul. This requires you to have the rear differential replaced completely—the housing, gears, bearings, seals, and fluids.
A typical rear differential repair costs anywhere between $200 and $400. These typical repairs would include your bearing, seals, and fluid changes. Of course, when a gear change is required, that’s when things get pricey. $1,500 is just the minimum you can expect to pay for new gears.
For a total replacement, you can expect to shell out up to $4,000 for brand new parts. If this is the only option you can always find a used rear differential assembly which will end up costing about half the price and may still be under warranty.
To Replace or To Repair?
Ultimately, the decision to replace or repair your rear differential depends on your wallet, your mechanic’s suggestion, and of course the actual issue at hand. A simple repair to keep your car on the road is nothing compared to a total replacement. But, when a replacement costs you thousands, is it worth it?
One important thing to consider is your car’s resale value. For example, if you have an SUV or truck that’s in good condition and is still in demand, there are certain upgrades that can add to its resale value. This means that if you have to replace certain parts, it may be beneficial to you if you plan to sell your vehicle.
The only downside to this is that you may have to replace or upgrade other components as well. If the upgrades don’t add more than $1,000 to the resale value, it probably isn’t worth it. You’ll also have to keep in mind that some upgrades can cause the resale value to decrease.
One last thing to consider with repairs is that severe damage to your differentials could mean damage to any of the attached parts. That could mean damage to the transmission, driveshaft, and axles—which means even more costly repairs.
You Can Always Junk Your Car
The truth is that sometimes replacing your rear differential will end up costing more than your car is actually worth. But that doesn’t mean you’re at a total loss. You can still junk a car with broken or faulty parts—and walk away with cash for it.
So, rather than stressing over repairs you can’t afford, get a free offer on your car today. We’ll buy your car from you—no matter what the condition of it is.