You hear an unpleasant noise from your car as you slow down. What could it be? An unexpected sound is often an indicator of a problem with the vehicle. Why do cars make grinding and scraping sounds in the first place? What are possible causes of those noises?
Grinding and scraping sounds from a car at a slow speed usually indicate that there is a problem with the CV joint, the brake rotors or pads, the transmission, the ball bearings, the timing chain, or possibly some other system in the vehicle. It is best to speak with a mechanic when the noise first appears, and address the problem in order to avoid further damage to the vehicle.
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Why Do Cars Make Grinding or Scraping Noises?
Any unusual sound is usually a sign that there is a malfunction in the vehicle. Look for any warning lights or indicators that light up your dashboard. Those will often give you a clue.
Any time your car makes a grinding or scraping noise, talk to your mechanic (unless the cause is something trivial like a steep driveway).
What Are the Causes of Grinding and Scraping Noises at Slow Speeds?
There are a number of possible causes that could make your car grind and scrape at low speeds. They all sound slightly different. Listen carefully to make a diagnosis, then fix the problem before it gets worse, or causes other problems.
Broken CV Joint
The CV stands for constant velocity. The constant velocity or CV joint is at the end of the drive shaft in 4-wheel or all-wheel drive vehicles. Some rear-wheel drive vehicles also have CV joints.
Its job is to let the wheel move independently from the car’s body. This makes for a comfortable ride and easy maneuverability.
What It is
CV joints can break or become damaged due to rough driving. Since they are on the bottom of the vehicle, they can scrape or get stressed on rough roads.
It is a common misconception that damaged CV joints only make noise when the car is turning. This is not true. A broken CV joint can make noise when the car is being driven straight at low speeds, too.
What It Sounds Like
A broken CV joint makes a repeated clicking sound during turns. It may also click when you’re driving straight. The vehicle also may shake and shudder during acceleration.
How to Fix It
The CV boot, which is a rubber casing around the CV joint, usually is damaged first. If you can catch the problem before the joint is damaged, replacing the CV boot is pretty simple.
If the joint is damaged, it will need to be replaced. Don’t wait. The CV joint is an important part of your car.
Bad Wheel Bearings
The wheel bearings are in the front wheel hub, and keep the wheel in place. They also keep friction to a minimum in the wheel. Friction will cause wear and tear on the wheel assembly over time, so intact wheel bearings are very important!
What It is
The wheel bearings are greased in order to keep them lubricated. They will generally last a long time if properly lubricated. However, if they start to fail, you will know it!
What It Sounds Like
Bad wheel bearings will make grinding sounds when you slow down and may make squealing sounds when you speed up. You may also notice a grinding sound when you turn.
How to Fix It
Fortunately, if you catch the problem early, the solution is as simple as adding more grease to the wheel bearings! This should give them a long life in the future.
On the other hand, if there was grinding in the wheel bearings for a while, they are probably worn out. If the wheel bearings are worn out, you will need to replace them.
Worn Brake Pads
Worn-out brake pads are the most common cause of grinding sounds when you’re slowing or braking. Brake pads are made of a steel backing with a friction material. They engage with the rotor when you step on the brake and cause the vehicle to stop.
What It is
The brake pads cushion the rotor by using friction. Over time, this friction wears down the material on the brake pad, and the metal on the brake makes contact with the rotor. This is the cause of the noise.
What It Sounds Like
You may hear grinding or squealing sounds as you apply the brakes to slow down. Braking will probably be less responsive than usual, too.
How to Fix It
Replacing brake pads is a simple, inexpensive fix that you can do at home, or at the mechanic. It’s a good idea to regularly check the wear on the brake pads, and replace them as they wear out, about every 10,000-20,000 miles, depending on your driving habits.
If the brake pads get too much wear, they will make extended contact with the rotor, and it can damage the brake rotors. A rotor repair is far more expensive and time-consuming, so it’s best to catch worn brake pads early.
Worn Brake Rotors
The brake rotors make contact with the brake pads in order to stop the car. They should be smooth and flat. When they wear out or get damaged, they can get grooves and become warped.
What It is
Unfortunately, brake rotors do wear out over time. Worn out brake pads, driving through water frequently, and hard braking can speed up the wear and tear.
With normal wear and tear, the brake rotors need to be replaced about every 70,000 miles and should be replaced in pairs, just like brake pads.
What It Sounds Like
The sound of worn brake rotors creates an unbearable grinding and squealing sound every time the brake is applied. There is no mistaking this sound!
How to Fix it
Warped or worn-out rotors cannot be fixed, and must be replaced. If you are mechanically savvy, you can do this yourself.
Failing Transmission
A failed transmission is a car owner’s worst nightmare. A transmission is often expensive to replace or repair. Sometimes, replacing a transmission is more expensive than the car is worth.
What It is
When the transmission is failing, it may be due to low transmission fluid, or failure in the gears themselves. The car will not run with a failed transmission.
What It Sounds Like
A failing transmission in a manual vehicle can make grinding sounds at low speeds. A failing automatic transmission will make more subtle humming and buzzing sounds. You will also notice rough gear transitions and shaking, or vibrating while driving.
How to Fix It
A failing transmission is no laughing matter. Don’t wait! If you suspect your transmission is failing, take your vehicle to a mechanic right away. It may only need more transmission fluid, but it is better to get it evaluated, anyway.
Final Thoughts
Don’t let grinding and scraping sounds from your car slow you down! Listen carefully to diagnose and address the issue. Remember, the sooner you deal with the problem, the least amount of damage will be caused to your car.
