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Summary
  • The humming noise usually stems from friction caused by a lack of lubrication.
  • Some problems that could cause the humming noise include uneven tire wear, damaged wheel bearings, faulty differentials, A/C failure, and more.
  • Getting rid of the humming sound usually involves repairing or replacing the part that’s causing it. The best way to prevent it is to check the tire pressure regularly and commit to regular maintenance.

Hearing a strange humming noise while driving is concerning, but don’t let it distract you. Instead, pay attention to its source, pitch, exactly when it happens, and its frequency.

Where does it come from? Does it get louder when you accelerate or stay at a consistent volume? Does it change pitches when you make turns or swerve?

Taking note of these details will help you determine its cause. Don’t ignore the issue to avoid complications down the line.

Common Causes of Humming Noise When Driving

The humming noise in a car that gets louder with speed usually stems from friction caused by a lack of lubrication, resulting in worn or damaged components. Some common causes include uneven tire wear, damaged wheel bearings, and A/C failure, among others.

Uneven Tire Wear

Tire cupping is a form of uneven tire wear that looks like a cup or orange surface. It usually develops due to unbalanced wheels, bad alignment, and underinflated tires. Tire cupping generates a humming sound because of the intermittent contact of the tire’s worn areas on the road.

Front-wheel-drive cars that have been driven too many miles between tire rotations may develop a loud tire sound that wasn’t there before the tires were rotated due to the fact that the rear tires developed a wear pattern that produces noise when these tires are rotated to the front.

So if the noise came about right after a tire rotation, have the alignment checked and consider having the tires rotated back to where they were before. But even if the rear alignment is in spec, the rear tires on a front-wheel-drive vehicle will develop a wear pattern that will make them noisy when they’re moved to the front after too many miles on the rear.

If the noise came about right after a tire rotation, have the alignment checked and consider having the tires rotated back to where they were before.

– Richard McCuistian, ASE Certified Master Automobile Technician

Damaged Wheel Bearings

flaking wheel bearings
The wheels carry the weight of the vehicle and each wheel is bolted to a hub connected to a shaft that spins inside a bearing. Some bearings last the entire life of the vehicle and make no noise at all. The rollers or balls and their races are very, very hard. But the metal will sometimes begin to flake, so that the bearing becomes noisy. | Image Source: Richard McCuistian
wheel bearing in damaged state
You can confirm bearing issues by listening to the sound as you’re changing lanes. Swerving to the left loads the right front bearing. If it gets louder when changing from the right lane to the left, suspect the right front tire or wheel bearing; it can be either one. | Image Source: Richard McCuistian

Swerving to the right loads the left the same way. But this can be misleading; sometimes it’s best to replace both front bearings at the same time. Many tire stores do this, not because of upsell, but because it’s a good practice. The same is true with the tires. A tire can look good and still be noisy, and sound just like a bearing. Sometimes a front tire will sound like a bad bearing in the rear. You see, noises telegraph.

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While it’s unlikely to happen, driving with a damaged bearing could also result in the wheel coming off, so it’s best to address the issue as soon as you can. Note, however, that vehicles are typically designed to prevent the bearings from throwing the wheels completely off. They may, however, wobble like cartoon wheels if the bearing totally fails and loses its marbles or rollers, and that’s dangerous.

Final Drive Bearings or Gears

The final drive consists of the ring gear and pinion, the ring gear carrier, and the small “spider” gears inside the carrier. These small gears are referred to as the “differential,” but they don’t usually make noise. It’ll be the ring and pinion or their bearings. The bearings will growl, and the ring and pinion gears will whine, and sometimes the whine will come and go with acceleration.

This gear whine noise is more prevalent on rear-wheel-drive vehicles with hypoid gears than on front- wheel-drive final drives that use helical cut ring and pinion gears. Hypoid gears are a matched set and must be changed in pairs. They have to be set up exactly right in regard to backlash, pinion depth, and bearing preload, or they’ll make all manner of noises.

hypoid gears and helical cut gears
Hypoid gears and helical cut gears | Image Source: Richard McCuistian

A/C Failure

The A/C compressor typically has a pulley that spins on a bearing. When the A/C compressor is engaged, the hub on the end of the compressor engages the compressor shaft when the clutch is energized, which spins a scroll or a swash plate so that it can pump refrigerant through the system.

bearings that carries compressor clutch pulley fails
If the bearing that carries the compressor clutch pulley fails (see photo) or if the compressor itself fails internally so that it can still spin but isn’t working right, the A/C compressor may produce a noise that changes with engine speed and/or A/C operation. If you hear a noise that goes away when the A/C is disengaged, it might be a compressor issue. | Image Source: Richard McCuistian

Damaged Fan Clutch

The fan clutch is a viscous link between the fan itself and the pulley that drives the fan. The viscous fluid in the fan clutch enables the fan to spin but not exactly at the same speed as the pulley that’s driving it.

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bimetal spring or electronic control change the valving inside the viscous clutch
As the air coming through the condenser and radiator heats up at road speed, a bimetal spring or electronic control will change the valving inside the viscous clutch so that the fan more closely matches pulley speed, moving more air. | Image Source: Richard McCuistian

If the fan clutch locks up completely, the energy required to drive the locked up fan will consume a lot of power so that the engine seems very noisy and fuel economy will suffer dreadfully. This video is a demonstration of this kind of failure:

Faulty Transmission

Issues within the transmission system, such as a worn planetary gearset in an automatic transmission or lubrication-starved gears in a manual  transmission will cause whining or humming. The crazy thing is that you can’t always LOOK at gears and tell when they’re the source of a noise – gears can look just fine and still be noisy.

Bearings can fail in transmissions as well; if a manual transmission makes noise in every gear except the direct drive gear (3rd or 4th) the input shaft bearing has failed, sometimes due to low lubricant levels, other times just because they began to shed metal from the races or balls/rollers.

Belt or Tensioner Issues

The front-end accessory drive (FEAD) belt system, as Ford calls it, doesn’t only spin the alternator, but it snakes its way around a lot of other pulleys as it delivers power from the large crankshaft pulley. It spins the alternator, power steering pump (if equipped), and water pump (if the pump isn’t driven by the timing belt or chain).

Idler pulleys have bearings that can fail, as do the other components. Some engines have manually tightened tensioners, others have spring-loaded tensioners. Cheap belts will stretch and can begin to make noise if you have a manually tightened style tensioner, but don’t over-tighten the belt or you can destroy other components.

, Humming Noise in the Car That Gets Louder With Speed: Common Causes, Fixes, and Prevention

Pro Tips are nuggets of information direct from ASE-certified automobile technicians working with CarParts.com, which may include unique, personal insights based on their years of experience working in the automotive industry. These can help you make more informed decisions about your car.

Pro Tip: If you suspect any of the belt-driven components to be the source of a noise, simply remove the belt and start the engine briefly (30 seconds or so) to see if the noise goes away. If it does, inspect the belt and spin each component with your fingers checking for rough or loose bearings.

The tensioner has an internal damper you can’t see, so if you’re replacing the belt because of a squeaking or chirping noise and you notice the tensioner bouncing while the engine is running, replace the belt and the tensioner and any rough or rattling pulleys.

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Many alternators have overrunning pulleys now with internal springs and clutches that can fail and make noise, so be aware of this as well.

Does a Worn CV Joint Cause a Humming Noise?

Constant velocity (CV) joints are located at each end of a driveshaft or drive axle. CV stands for “constant velocity,” meaning, they provide smooth power through a wide range of angles during driving and suspension events.

When CV joints begin to wear out, they don’t hum, they click during turns. This usually happens because the CV axle grease boot has split and has allowed dirt and moisture to enter the joint. But sometimes even if the boot is intact, the joints can wear out. Check the CV boots for telltale cracks, tears, or grease leaks.

How to Get Rid of the Humming Noise in Your Car

How to resolve the humming noise depends on what’s causing it.

The easiest and most effective way to deal with the humming noise is to replace the damaged or worn-out components causing it. First though, you have to isolate the source of the noise.

How to Prevent the Humming Noise in Your Car

Some ways to keep your daily driver from making a humming noise when driving is by regularly checking the tire pressure and following your regular maintenance schedule.

Check the Tire Pressure

One of the biggest causes of uneven tire pressure is under or overinflated tires. Incorrect tire pressure results in certain areas of tire rubber making more contact with the road. The increased friction leads to inconsistent and premature wear.

Checking the tire pressure and adjusting it as needed would do wonders for your tire’s lifespan. You can find the appropriate amount of pounds per square inch (psi) on the tire itself or in your owner’s manual.

Follow the Regular Maintenance Schedule

Regular maintenance lets you check your vehicle’s different components and systems. This means you can prevent the humming noise by spotting faulty parts before they cause issues.

Regular maintenance usually involves oil changes, tire rotations, and alignment on top of the visual inspections. There should be a recommended maintenance schedule you can follow written in the owner’s manual.

About The Authors
Written By Automotive and Tech Writers

The CarParts.com Research Team is composed of experienced automotive and tech writers working with (ASE)-certified automobile technicians and automotive journalists to bring up-to-date, helpful information to car owners in the US. Guided by CarParts.com's thorough editorial process, our team strives to produce guides and resources DIYers and casual car owners can trust.

Reviewed By Technical Reviewer at CarParts.com

Richard McCuistian has worked for nearly 50 years in the automotive field as a professional technician, an instructor, and a freelance automotive writer for Motor Age, ACtion magazine, Power Stroke Registry, and others. Richard is ASE certified for more than 30 years in 10 categories, including L1 Advanced Engine Performance and Light Vehicle Diesel.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

NTMS Scientist
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