Commanding a huge hunk of metal around a corner can be nerve-wracking enough without having the action be accompanied by suspicious sounds. If your vehicle has ever made strange noises while turning or accelerating, you need to take a closer look at the differentials. Once you understand the function of those parts of your vehicle, learning how to quiet a differential whine will be a piece of cake.
Located between the engine and the wheels, differentials allow your vehicle to turn effectively. The gear train components adjust the number of rotations each tire has to do while turning or shifting speeds. If you need to turn left, the front left tire will have the lowest rotational speed while the rear right one will have the highest speed. That variance is what your front and rear differentials are supposed to achieve.
Needless to say, these gears should ideally operate at a low level of noise. Since we’re talking about moving parts, you can’t really expect absolute silence. Still, the sounds coming from the engine are usually louder than anything the differentials can produce. So what should you do if that is no longer the case?
Which Car Parts Can Cause Humming, Whining, or Grinding Sounds?
Firstly, you’ll need to learn how to recognize the array of sounds that might come from your vehicle’s differentials. As we have established, you shouldn’t hear anything during standard operation. Squeaky breaks and rattling dashboards and doors are usually loud enough to cover all other sounds.
Still, if you happen to hear whining or howling sounds as you turn or accelerate on the road — it may have something to do with these components. Of course, they’re not the only parts that could have that effect on your vehicle. Other suspects include the wheel bearings and the tires themselves.
Both of these parts could develop performance issues that would make them produce louder humming or grinding sounds. Jacking up your car and manually spinning each tire will tell you if the problem lies in the wheel bearing. But you can always perform that test before you start the process of replacing the differential fluid.
Conversely, a simple visual inspection should be enough to determine whether you have unevenly worn, cupped tires. However, uneven tire wear and handling difficulties could also be the result of a faulty differential. Either way, you’ll have to take the car for a spin to find the exact source of the noise.
What Does Differential Whine Sound Like?
On your drive, you should take turns having the windows up and down while you accelerate, decelerate, and turn corners. That will help you understand where the noise is coming from. Depending on the part that’s causing the noise, you may be able to pinpoint the fault to a single tire. However, if the differentials are to blame, you’ll hear the sound coming from the space between the front or rear wheels.
Many people report hearing a distinct whining sound that turns into a louder howl as they push their vehicle to go above 20 miles per hour. That noise can be a symptom of a wide range of issues, though it usually comes down to loose bearings. However, malfunctioning differentials can produce other sounds as well.
Namely, if the gears inside aren’t lubricated enough, you might hear rumbling or clunking noises. On top of that, rhythmic thumping sounds could even indicate a broken ring or pinion gear.
What Causes a Differential to Whine?
When addressing automotive malfunctions, some people prefer replacing faulty parts to fixing them. Sadly, getting a new differential can set you back anywhere between $1,500 and $4,000. So let’s just say that fixing the issue that’s causing the noise you hear is your best bet.
Of course, the matter will ultimately come down to the severity of that underlying problem. With that in mind, it’s time to discuss the things that might be causing one of your differentials to whine.
As we have established, that particular noise could be triggered by worn rings and pinion gears. Those components could also cause more rhythmic clicking, clunking, or banging noises. On the other hand, if the sound you’re hearing could be characterized as whirring, the issue is more likely with the pinion or carrier bearings.
But really, unless you have special training, you won’t be able to identify those parts when you see them. With that in mind, you might find this video helpful. It should explain the interior components of a differential, how they work, and how they might malfunction.
Another common cause of differential issues could have something to do with the gear lubricant. Namely, to function optimally, the inside of the differential needs to be fully submerged in oil.
If the gasket has deteriorated enough to let the fluid drain from the chamber, the gears will have a hard time turning. On top of that, if you often drive off-road and through deeper puddles, the oil might have gotten mixed in with water. As you can imagine, that will likely result in all manner of strange sounds.
How to Stop a Differential Whine
Ultimately, there’s only one thing you can do to optimize the performance of your differentials from the comfort of your garage. While you can’t go around replacing the gears inside the component, you could easily swap out the fluid even if you don’t have any experience fixing cars. So without further ado, let’s get to it!
1. Elevate the Vehicle
Since the parts you’ll need to access are located on the bottom side of your vehicle, the first thing you’ll have to do is elevate it. In this case, you’ll have to lift your car at least a foot or two off the ground so you can get under it. You can lift it onto some jack stands or use a ramp — that part will be up to you.
Before you crack open the noisy differential, you should get some supplies ready. You’ll need:
- A half-inch torque wrench
- An oil drain pan
- Some clean rags
- A flat pry bar or screwdriver
- A can of brake cleaner
- Some differential oil
- A utility knife or gasket scraper
- A new gasket in the shape of the differential cover
- Flexible tubing that fits the fill hole or a lubrimatic fluid pump
Once you have all these things lined up next to your vehicle, you’ll be ready to work on the differential.
2. Loosen the Fill Plug
Before you drain the diff fluid out of the chamber, you should figure out where the fill plug is. Depending on the kind of differential you’re working on, that access point could either be just above the differential or on the cover itself, as is the case in this video. Either way, you’ll want to find it and try to open it.
If you’re unable to open the fill plug even with a healthy helping of WD-40 spray and your mightiest torque wrench, you shouldn’t try to drain the differential yourself. Instead, you should get a second opinion. After all, if you were to drain the chamber only to find out you can’t fill it back up yourself, you’d have to get your vehicle towed to your mechanic.
That’s why you’ll want to try to loosen the plug before you do anything else. Don’t fully open it just yet — knowing that you can is enough for now.
3. Drain the Fluid
After you’ve made sure the fill plug is workable, you can start dealing with the bolts that are holding the differential cover in place. As you’ll see, the part is positioned vertically. And if it’s anything like the one in this video, it may have a drain hole you could open first.
If not, you could just get the black ooze out by getting the bolts off with a torque wrench. In either case, you’ll want to have a drain pan ready to catch the mess.
If the bolts are the only thing standing between your drain pan and the diff fluid, you should start getting the bottom ones off first. As you work your way up, keep the topmost bolt in — don’t go further than loosening it. That should prevent the cover from dropping into the drain pan along with the contents of the differential.
Now, there’s a chance that the cover won’t pop off or start leaking even after most of the bolts are out. That might indicate that the old gasket and oil have created a seal around the edge of the cover. In that case, you’ll need a slim tool — like a screwdriver or a pry bar — to get the lid off.
After you crack the seal, the tar-like fluid should pour out without an issue. After that initial gush of liquid is out, you’ll be able to take the topmost bolt out and take the cover off fully.
4. Clean the Differential Cover
At this point, you can let the diff fluid continue draining into the pan while you clean the cover. To pick up the thick layer of oil coating the inside of the lid, you can use paper towels or fabric rags. Either way, you should take care not to leave any debris on the inside of the lid.
If you have issues getting the diff fluid off the cover, you can hit it with a brake cleaner. However, it should be easy enough to clean as long as you have patience and a steady supply of shop rags.
As you get the oil off the cover, you may notice some stubborn black residue around the rim. That’s probably a mixture of oil and the old gasket that prevented the fluid from leaking out of the differential. Before you can put a new one in place, you’ll need to scrape that residue off with a utility knife, a scraper, or a Scotch-Brite pad.
You could even get the job done with a wire brush, as long as you don’t scratch up the surface too badly. Grooves in the metal could prevent the differential from closing properly even with the new gasket in place.
5. Clean the Inside of the Differential
Next up, it’s time to clean the inside of the differential chamber. With this step, you’ll want to start by scraping the remnants of the previous gasket from the rim. But before you reach for your scraper, try to cover the inside of the differential with rags. That should prevent any debris from getting on the gears.
After getting the old gasket off the rim, you can take the rag off the gears. Mind that none of the debris that may have landed on the rag ends up inside the chamber. Once you take care of that, use brake cleaner to get the oily residue from the gears and the rim. Use another clean rag to wipe away any dirt.
If the inside of the differential looks good, you could just put a new gasket on the differential cover and bolt it back on. Don’t fully tighten the bolts as you go around the cover. You’ll need some wiggle room while you get them all in. Once all ten or so bolts are in place, feel free to tighten the fit.
Of course, if you suspect something isn’t right with the internal components, now would be the time to call in an expert. Otherwise, you can move on to replacing the differential oil.
6. Replace the Fluid
At this point, it’s time to go back to the fill plug you loosened before you took off the differential cover. After you take it off, you’ll use a length of tubing or a fluid pump to get the differential oil from the bottle to the fill hole.
You’ll want to keep pouring until the liquid starts coming back out through the hole. Since we’re talking about transferring a fairly viscous fluid from one point to the next, the process might take a while. In the video, the job required two and a half jugs of oil, but that will depend on the capacity of the differential you’re working on.
When you see the fluid coming back up to the fill hole, you can simply put the plug back on. Finally, you’re ready to take your car for a spin!
7. Test Drive Your Vehicle
Unless something is seriously wrong with the internal parts of your differentials, replacing the lubricant should eliminate any disturbing noises. Still, you know what they say — it ain’t over ‘til it’s over. You’ll have to make sure the sound is gone before you start patting yourself on the back.
Don’t worry, testing the efficacy of your treatment should be a matter of going for a quick ride. You’ll have to push your car well above 20 miles per hour, then decelerate to check if that action prompts any suspicious noises. While you’re at it, you should take a few turns as well. Additionally, opening and closing the windows should help you understand the noise better.
Just remember that most vehicles already make all sorts of noise while on the road. So if you want to be able to isolate the sound of the differential, you should take steps to make your car quieter in general. After all, if you have a loud exhaust or noisy lifters, you won’t be able to hear a malfunctioning differential.
Can You Drive With a Noisy Differential?
At this point, you might find yourself wondering how long you can continue driving with a noisy differential. Perhaps you have a road trip coming up and are wondering if you can postpone dealing with the issue until you get back. Alternatively, you might have already tried to fix the cause of the noise only to end up right where you started. Either way, the question of safety should be at the forefront of your mind.
Unfortunately, you may not like the answer you’re about to get. On the one hand, you’ve probably already driven with a noisy differential by this point. But just because you can drive with faulty parts doesn’t mean that you should.
Remember, differentials are a crucial component of your car’s steering system. If those components are misbehaving to the point of producing sounds, you should address the underlying issue as soon as possible. Fixing it is in your best interest. In fact, if you want to implement some preventative measures, you can make a habit out of replacing the gear oil every other year.
Even so, you might get a completely different answer from your mechanic. In that case, make sure to ask them if their recommendation is coming from the cost associated with the fix or a genuine belief in the safety of the differential in question.
Sometimes, mechanics avoid recommending replacements simply because the cost is too high. Between the parts and the labor cost, fixing a differential could set you back up to several thousand dollars. But if you’re willing to invest in your vehicle for the sake of safety, your mechanic should take that into account before issuing their final recommendation.
What Are the Other Symptoms of a Noisy Differential?
When it comes to fixing a noisy differential, there’s no time better than the present. Still, if you need any more convincing, we could quickly go over the other symptoms that will accompany the whining sound.
As we have established, the noise a differential makes will be most evident while you’re accelerating and turning corners. That means that those are the times you will struggle to maintain control of your vehicle. If a differential is malfunctioning, you will find it difficult to steer, particularly when you’re traveling at high speeds.
Moreover, if the gears stop turning due to low lubrication or faulty parts — your tires could lock up. In fact, tire troubles are a common sign of differential malfunctions.
Remember, differentials are supposed to convert the power coming from the engine into wheel rotations. During standard operation, these components should alter the number of rotations each tire takes as the vehicle turns.
So if a differential isn’t functioning properly, it could make all the wheels spin at the same rate even during turns. Even if that doesn’t make the vehicle get out of control, it’s sure to lead to uneven tread wear. And who would want to buy a new set of tires instead of just getting some synthetic lubricant?
With any luck, that’s all you’ll need to get your car to stop whining at the most inopportune times. So ultimately, cleaning out the differentials and putting in new oil should solve several of these problems for you.