How To Quiet Differential Whine

If you notice that your car makes an odd noise whenever you accelerate, decelerate, or corner, your differential may not be in working condition, even though these parts require little maintenance on average. Most often, differentials fail whenever they are overloaded when towing or when there isn’t enough differential fluid to lubricate or dissipate heat from a leak.

If the whining or howling noise occurs whenever you slow down, the sound is most likely due to a bad pinion bearing. In contrast, a whining noise while accelerating is most often due to overloading or lubricant levels. Needless to say, there could be a couple of different reasons for a whining differential.

In this article, we’re going to look at some ways to quiet a differential whine. Because there are many potential causes for the sound, it is most important to determine the cause for yourself so that you can fix the issue accordingly. Let’s get started.

Materials Needed

• Jack stand
• Blocks for back wheels
• Assistant/helper
• Differential oil
• Oil pump
• Can brake cleaner
• Clean shop rags
• Drip pan
• Limited slip additive 
• Seal removal tool ; installation tool
• Screwdriver(s) flat and Phillips head
• Socket set and ratchet
• Replacement differential output seal
• Replacement rear end oil
• Plastic gasket scraper
• Torque wrench

Step 1: Diagnose the Noise

To begin, you need to diagnose the differential noise. Sometimes, it can be difficult to determine whether the noise is coming from a differential or a wheel bearing. That’s because they produce similar sounds, and they even affect the driving experience similarly. Diagnosing the noise ensures that you are treating the actual issue.

To diagnose the noise, go to an empty road and drive around 50 mph. Pain attention to the noise. As you accelerate, listen for a howling sound. Continue listening for the sound as you cruise. Then, slightly turn the wheel left and right to see if the noise increases whenever you turn.

Remember, drive safely, and don’t lose control of the vehicle in the process. Keep both eyes on the road!

If the howling gets louder whenever you steer to the left, the left wheel bearing is to blame. Similarly, it is the right wheel bearing if the sound gets louder when you steer to the right. If you hear no difference in the howling when you turn either direction, it is the differential that is causing the issue.

You can further confirm that the differential is to blame by putting it on a jack stand and testing the tires. You will need an assistant or helper for this test.

Make sure the drive wheels are off the ground and stop the back wheels with blocks. Turn the engine off and shift the car to neutral. In most cars, you should be able to spin one of the drive wheels while the other one is held still. If you can’t do this, the differential likely needs attention.

The only exception to this test is when your vehicle does not have open differentials.

Once you have confirmed that it is likely the differential making noise, think back to when you heard the noise most. If the howling was at its worse when you were decelerating, you likely have a bad pinion. In contrast, howling while accelerating is often due to overloading or lubricant levels.

Of the possible issues, low lubricant levels is the easiest to fix. It doesn’t require many parts or money, making it easy to fix. The other issues, such as a bad pinion, are unfortunately difficult to fix and may require some skill, experience, and money.

Step 2: Replace the Differential Fluid

Once you know that the differential needs repair, it is important to act swiftly. This part will get more and more expensive to fix the longer you wait. Be proactive in your treatment so that you don’t have to spend more than you need to.

The easiest way to quiet a whining differential is by replacing the differential fluid. This option will work for most people unless the differential is broken in other ways. Since differentials last a long time, replacing the fluid should be enough for most needs.

To replace the differential fluid, you will need to look at your automobile’s owner manual. The owner manual will tell you exactly when the fluid needs to be changed. As a general rule of thumb, you should replace the differential fluid every 30,000 to 60,000 miles for the front differentials and every 30,000 to 50,000 miles for rear differentials.

Begin by placing the vehicle on a jack stand or ramp. Find the differential drain bolt to loosen and remove it, allowing for oil to drain completely. To ensure that the differential parts are still intact and that the automobile simply needs more fluid, drain the remaining fluid. If you do not see any small pieces of metal, simply replace the oil. This should solve many howling issues.

To replace the oil, remove the gear oil fill bolt and use a pump to add the gear oil to the differential. Add as much as recommended based on your vehicle or until the oil dribbles out the fill hole. Tighten the fill hole bolt and wipe away any excess oil.

Step 3: Replace the Seal

If you found that there were small pieces of metal within the drained oil, you need to go a step further than simply replacing the differential fluid. Little metal pieces typically mean that there is some sort of issue that needs to be resolved. Remove the cover plate, clean it, and inspect it.

You will likely need to replace the seal. Replacing the seals will largely be needed if the whining has been going on for a while and it is excessively loud. Once the seal is replaced, replace the differential fluid just as we described in step two.

Similarly, you will need to replace the seal if you see any leaks from the differential. The quickest way to find a differential leak is to look for gray, black, or brown fluid on the garage floor, driveway, or wherever you park your car. This is a sign that a seal is broken or gone completely. Once again, replace the seal and the fluid inside.

To replace the differential output shaft seal, you’ll probably need three to five hours to complete the project. The vehicle should be on a jack stand so you can remove the seal. For the best results, opt for a hydraulic lift. Remove the wheels and tires using an impact wrench or star wrench.

You may also need to remove the axle, but we will touch on that more in step 5.

Step 4: Test the Automobile

Most of the time, replacing the fluid or the seal will solve the issue. Test the automobile by driving it around and seeing if the whining is fixed. Simply repeat the driving test from step one. If the issue is resolved, great. Your issue is solved, and you don’t need to do any of the remaining steps.

However, if you still hear a whining sound, then there is likely an issue with the parts of the differential. These will be more difficult to fix, and they will be more expensive. Continue on through the next steps to fix the most common broken parts of a whining differential.

Step 5: Inspect the Rear Differential Gasket and Pinion Seal/Side Seals

Inspecting parts within the differential is more difficult than replacing the fluid. There are typically two parts that will commonly cause whining: the rear differential gasket and the pinion seal or side seals. The rear differential gasket is relatively easy to inspect, but the other two are more complicated.

To inspect the rear differential, you will need to drain the oil. You should be able to see if it is broken or needs to be replaced. The side seals, on the other hand, are a bit more difficult to inspect. You will need to remove axle shafts and any leaky seals before reassembling.

To remove the axle, you will need to consult your user’s manual about the following components:

• Brake caliper
• Emergency brake
• Shock mounts
• Spindle nut
• Tie rod ends
• Wheel bearings

Before removing the broken seal, stuff the differential with a clean rag. This will protect it from the elements whenever the seal is removed. Use a seal removal tool or a flat screwdriver to displace the seal from the housing. Make sure not to scratch or damage the inside of the differential in the process.

Step 6: Clean the Housing

Even after a differential has been fixed, many people hear a whining again because the housing wasn’t properly cleaned in the process. Grab a clean rag and brake cleaner to clean the inside parts of the differential. Remove any excess materials or broken parts.

Clean the axle male fitting as well. Once again, spray a lot of brake cleaner to the male fitting and axle gear. Clean off all grease and debris so that they fit correctly.

Step 7: Get the Needed Parts and Repair

After you have inspected all the parts, it’s time to figure out what you need. You might need to order new seals, replacement fluid, gear, and more. Replacing any pitted or damaged bearings will require you to dismantle the differential, as well as possibly replaced pinion seals. This will likely take you three to five hours to complete.

If there are any chipped or worn teeth on the gear, you might need to replace bearings, gears, or miscellaneously broken pieces. More than likely, this will take 6 to 8 hours to repair if the parts are on hand. If you have to order the parts, it will obviously take longer.

No matter what parts you need, make sure you get models that match your automobile. It is helpful to keep the old parts for comparison when you remove them. This ensures that you get the right make and model based on your vehicle.

Step 8: Lubricate and Add Differential Fluid

Now, you need to add the fluids to the parts. More specifically, lubricate the axle ends using fresh gear oil. This will allow the gears to attach to the inner gears of the differential. When you reinstall the axle into the differential, ensure that they are lined up correctly. You may want to mark the location while you are removing them to aid in this step.

After everything is lined up correctly, tighten the bolts and attachments. Obviously, that should be in reverse order than above since you are putting them back on. Add differential fluid after the parts are reassembled and lubricated.

You may need to read your service manual to learn about your vehicle’s steps. Different automobiles will require different preparation, parts, and oil.

Step 9: Assemble

Finally, it is time to reassemble everything. At this point, the differential should be put back together, but the wheel and tire may still be off. Put the wheel, tire, and lug nuts to the recommended settings so that the vehicle can be used once again.

With everything intact, go one last time to the differential and make sure all bolts are tightened. A final check-up ensures that everything is in order for a safe and enjoyable riding experience. Now, you’re free to take the vehicle off the jack so you can test it out.

Step 10: Test It Out

After you have repaired the differential, you should probably test out the vehicle to make sure the issue has been resolved. We recommend driving the vehicle for at least 15 miles. If everything was corrected correctly, you shouldn’t hear any whining or noises coming from the differential.

After the drive, you also need to inspect the housing to make sure everything is sealed properly. Look underneath the vehicle to see if fresh fluid is leaking. Adjust as needed if you see fluid underneath.

If the vehicle is still making a whining or other weird noise, you may need to contact a certified mechanic to help you out. This part is difficult to properly assess and fix if you do not have their proper experience.