Does your car make grinding, howling, or other odd sounds when you accelerate, decelerate, or round a corner?
If yes, one possible cause is that your differential is not in proper working condition.
Possible causes of differential whine include overloaded when towing or when the differential fluid runs out.
If you find that your car howls or whines when you slow down, this is most likely caused by a bad pinion bearing.
On the other hand, differential noise on acceleration is most likely due to overloading or lack of differential fluid.
There isn’t just one possible cause or solution to fix differential whine.
If you’ve been wondering how to quiet differential whine, this article should help you a great deal.
What is a differential on a car?
The differentials on a car are the gears that change the direction of torque from the engine equally between the drive wheels.
Differentials types include front-wheel drive and rear-wheel drive.
They are usually found on the rear axle of rear-wheel-drive vehicles and placed in the bulge in the axle.
In contrast, front-wheel differentials are located at the end of the transverse-mounted engine.
4-wheel drive vehicles have both front and rear differentials that lock together when in use to deliver the same power to both axles.
All-wheel drive vehicles include a third differential which can be found between the front and rear axles.
This third differential is what makes it easy for the steering axle to turn at varying speeds when rounding a corner.
Other vehicles may include split or co-axial differential.
This allows the left and right wheels to rotate at different speeds on uneven surfaces and when cornering.
An example of this type of axle is limited-slip differentials that transfer torque from one axle to another if one tire is spinning due to ice, mud, or wet pavement.
Differentials are made up of different gears that help to rotate engine power to both the left and right wheels.
The gears are called planet gears and sun gears.
Planet gears spin around or can be driven by sun gears.
An input pinion turns the pinion shaft that is located at the end of the drive shaft.
This allows it to mesh with the ring gear which has the left or right axle going through it.
At the end of each axle is the side gear also known as the sun gear.
The sun gears are driven by two spider gears(pinion gears).
When the engine turns the shaft it turns the input pinion at the same time which then turns the sun gear.
The rotation of these gears is what delivers drive power to the wheels.
What can cause a bad differential sound
It’s no surprise that every vehicle makes noise whilst being driven.
You hear everything from the sound of the engine humming to the sound of tires against the road.
However, odd sounds that stand out are a clear indication that something is amiss and you should probably get it checked out.
Differentials can last for thousands of miles and usually require little to no repairs.
However, they may require some maintenance if you are experiencing, clunking, grinding, howling, and whining.
So what can cause a bad differential sound?
Let’s talk about some noises you may hear when your differential isn’t in working order and the possible causes are?
If you are hearing a loud humming sound that stands out, it can be due to a worn pinion bearing.
Clicking or ticking noises when slowing could mean that there is a problem with the side-gear.
Clunking and clicking can be caused by a broken tooth on a pinion or ring gear.
Your vehicle can click or tick due to problems with your lifter.
Check out how to diagnose and fix a lifter tick in this article.
Squeaking or grinding sounds when driving could be an indication that a universal joint is damaged or worn.
Whirring sounds can be caused by worn or pinion bearings.
Knocking or clicking can be a result of a worn axle shaft spline or chipped gear teeth.
If you hear a low pitch rumble when reaching speeds greater than 20mph. it could indicate that a carrier bearing is worn.
However, if the rumbling gets worse when you perform a hard turn, it’ most likely a worn wheel bearing.
Clunking and banging sounds can be caused by worn spider gears, clutches, or lack of lubricant.
The sounds would be heard when cornering, reversing, or slowing down too quickly.
Whining sounds are a result of a loose gear inside the differential.
Rear differential noise when turning and front diff noise can be a result of loose gears.
Steps to diagnosing differential noise
Diagnosing differential noise can be problematic since it can be hard to tell the difference between a differential needing attention and a failing wheel bearing.
They can produce the same types of sounds and affect driving in a similar manner.
First things first, take your vehicle for a drive on an empty road and maintain a speed of 50mph.
Listen if there’s any howling sound when you accelerate.
Try turning the wheel slightly to the left and right and listen if the noise can be heard, stays the same, increases or decreases.
If you find that the noise increases when steering left, the left wheel bearing is most likely the culprit and the opposite when steering right.
However, if the noise remains the same, it could be the front or rear differential.
If you’re not sure whether it’s a worn wheel bearing or trouble with differentials, check how long will a wheel bearing last after it starts making noise for further diagnosis.
How to quiet differential whine
If you’re wondering how to fix a noisy differential, then you will be glad to know that you just might be able to do it yourself if you’re mechanically inclined.
You’ll need some tools and a bit of time to perform some of these fixes.
Keep in mind, that it is recommended to have your vehicle looked at as soon as you hear odd noises.
If you don’t know your way around a vehicle, visit an experienced mechanic to help diagnose and fix the issue.
Continuing to drive your vehicle not only cause more damages which can cost you but can also put your safety in jeopardy.
Prep the area
You will also need to place your vehicle on a jack stand or ramp to have easy access to the differentials.
Differentials can come in different designs and depending on the type your vehicle has will depend if it is going to be a messy or tidy job.
Some differentials have drains plus while others will need to have their housing cover removed.
However, in both cases, you’ll need a wide catch pan to drain the fluid.
Replace Differential Fluid
Review the owner’s manual to have an idea of how often, the differential fluid needs changing out.
If it is way past its time and there are no leaks, you will need to drain the oil and replace it with fresh new liquid.
As mentioned before, you’ll either that a differential with a drain plug or one where you’re required to move the housing.
If your differential design features a drain plug then remove the fill-hole plug at the top of the differential casing and unscrew the plug.
If you have to remove the differential housing to drain the fluid, remove some of the housing bolts and unscrew some loose enough to keep the cover in place.
Pry open the cover gently with a screwdriver or risk getting sprayed with the old smelly differential oil.
After draining, inspect the fluid and if there are no metal pieces, then the changing of the oil is enough to stop the whining.
Differential fluids are all labeled differently and finding the most compatible one for your vehicle is important.
Replace the seal
If you observed small pieces of metal in the drained oil, then you need to move on to the next possible solution.
For this, you’ll need to remove the cover plate fully, clean it and inspect it.
You may have to replace the seal especially if the whining is exceptionally loud and has been going on for some time.
Once the seal and the fluid are replaced, the noise should be gone.
Seals will need replacing as well if there is a differential leak.
Look in spots where you usually park and see if any black, gray, or brown fluid appears on the ground.
If you do see such spots, then a seal is broken and needs to be replaced.
Do note that if you have to replace the differential output shaft seal, you’ll need 3 to 5 hours perhaps to complete that task.
Place the vehicle on a jack stand and opt for a hydraulic lift to make removing and replace the seal easier.
You’ll have to remove the wheels, tires, and even the axle.
Test the Vehicle
Majority of the time, replacing the differential fluid or seal will eliminate any whining.
After doing these, you can take the vehicle for a test run to determine if the whining has stopped or if it can still be heard.
If there is no whining sound, then great, there is no need to do anything further.
However, this is not the case all the time and you may still hear the whining sound.
This means that there may be a problem with the parts of the differential.
These problems can cost a lot and can also be difficult to fix but with a little patience, you just may be able to do it yourself.
Inspect rear differential gasket, pinion seal, and side seal
This is where things can get difficult and tedious and you’ll have to inspect the4 parts within the differential.
There are a few parts of the differential namely the rear differential gasket, pinion seal, or side seals that can be responsible for the whining you hear.
The rear gasket is fairly easy to check but the other parts can be a bit more complicated.
Inspecting the rear differential, you simply drain the oil and have a look to see if it is broken or needs to be replaced.
To inspect the side seals require a bit more work and you’ll be required to remove the axle shafts to do so.
If you’re not sure how to remove your axle shaft, look up videos with a make, model, and year similar to your vehicle and go from there.
You can also consult your owner’s manual if you have it on hand.
The owner’s manual is going to guide you since it’ll have information about the brake caliper, emergency brake, shocks mount, spindle nut, tie rod ends, and wheel bearing.
This way you remove the axle safely without damaging the other parts.
Once the axle is off, look for broken seals and if you do see one, do not remove it just yet.
Stuff the differential with a clean rag first before attempting to remove the broken seal.
The rag will protect the differential from outside elements when the seal is removed.
You can use a seal removal tool or flathead screwdriver to carefully remove the broken seal from the housing.
Clean the housing
Oftentimes, people neglect cleaning the differential housing which is why even after fixing all the issues, your differential still whines.
Cleaning the housing is easy as using a clean rag and brake cleaner to clean the inside of the differential.
Saturate the male fitting and the axle gear with brake cleaner and wipe off all the grease and debris so they fit and work correctly.
Replace broken parts
Fixing differentials may require you to order new parts like seals, bearings, gears, etc.
If you have to replace pitted or damaged bearings, you’ll have to dismantle the differential and most likely replace pinion seals as well.
If the gear is chipped or worn, you’ll need to replace the bearings, gears, and other broken parts.
Make sure you get parts that are compatible if not exact to the broken ones.
Lubricate and re-install axle into differential
After, replacing the old and broken parts, you’ll need to lubricate everything and add differential liquid.
Pay special attention and lubricate the axle well so that the gears attach to the inner gears of the differential well and everything is rotating smoothly.
Once everything is lined up, it’s time to tighten the bolts and attachments to reinstall the axle into the differential.
Assemble and test drive
After you reinstall the axle into the differential and everything is back in its right place, it’s time to put back the wheel and tires.
Give the differential one last glance over and make sure all the bolts are tightened.
Do a final check-up to ensure everything is back in position and in working order before removing it from the jack and testing it out.
If all is well, it’s time to remove the vehicle from the jack and taking it for a test run.
Do a test drive for about 15 miles and during this time you shouldn’t be hearing any whining sounds.
After the test drive, inspect the differential again.
Look to see if there’s any fresh fluid on the ground and apply the fixes mentioned above until there’s no leak.
However, if your vehicle continues to make odd noises, contact a certified mechanic who is experienced enough to diagnose and fix the problem for you.