Clunking Noises When Accelerating And Decelerating – Explained

At some point, most drivers had to deal with different car noises, which might indicate something wrong with the car.

While some of these noises can mean minor repairs, you should never ignore any noise that isn’t normal.

Here’s what can cause a clunking noise when accelerating

When accelerating or slowing down, a clunking noise from the front of your car can indicate weak motor or transmission mounts, a failing drive shaft, a failing shift solenoid, or a low transmission fluid level.

man driving his car

1. Worn motor mounts

From my experience as a car mechanic, if you can hear the clunking noise mostly when you hit the gas pedal, it is probably a bad motor mount. Most customers will fail to reproduce the sound when they bring the car in for a diagnosis. However, there are other ways to identify a broken mount.

What is a motor mount?

Even if you are familiar with cars, it is possible that you never had to deal with a motor mount. As the name suggests, your engine relies on multiple mounts that hold it in place. When the engine is running, it produces different levels of vibrations that can make the driving experience feel worse.

Engine mounts are made from rubber and do an excellent job at dampening vibrations. On newer cars, mounts can have a fluid inside, which helps even more in reducing vibrations.

High-end cars can use vacuum-controlled mounts that significantly reduce the amount of sound and vibrations getting into the cabin.

Common signs of a bad motor mount

Although you do not need to service engine mounts, they do break and need replacing after a few years. Signs of a bad motor mount include:

  • Clunking or banging noises coming from the front of the car, as the engine starts moving and hitting other parts
  • Worn mounts can lead to increased vibration while driving the car
  • The ride might not be as smooth as before, as you might notice a jolt when changing gears
  • You might experience a lurch when starting the car
  • A close visual inspection will tell you if the motor mounts are worn and need replacing

How much does it cost to get it replaced?

Replacing a motor mount is not easy nor cheap. It is one of those jobs where the labor will cost you more than the actual part. Expect to pay anywhere from $400 to $600 for labor and parts. If you have more than one mount that needs replacing, your cost will be higher.

How long does a motor mount last?

Engine mounts will last up to 10 years, depending on the build quality and the car’s drive. Inspecting them regularly will ensure your vehicle will drive as smoothly as possible, and you can prevent further damage.

2. Worn transmission mount

Another common issue that might cause your car to make a clunking noise can be a worn transmission mount. Transmission mounts work the same way as motor mounts.

They can be made out of rubber, while the better ones are hydraulic mounts. The latter does a much better job of dampening vibrations and sounds.

Signs of a worn transmission mount

A worn transmission mount will have the same symptoms as a worn engine mount.

  • Excessive noise and vibration
  • Clunking and banging sounds coming from transmission area
  • You might feel a jolt when changing gears

You can also perform a visual check of the transmission mounts for any damage.

Cost of replacing a transmission mount

Replacing your transmission mount is not an easy job. I don’t recommend attempting this as a DYI job unless you have experience working as a mechanic.

Replacement costs will start around $400, as it is a similar task to replacing a motor mount.

3. Low transmission fluid

Low transmission fluid can be the cause of the clunking noise you hear occasionally. Although transmission fluid does not require changing like engine oil, it is recommended by some manufacturers to replace your transmission fluid every four years or 100,000 miles.

Signs of low transmission fluid

Here is a list of signs that indicate your transmission fluid might be lower than required:

  • Slipping gears
  • Warning light ON
  • Clunking noise when changing gears
  • Leaks of red fluid on the ground
  • Burning smell from overheated transmission fluid

If you experience any of these signs, it is essential to have your car inspected as soon as possible by a certified mechanic. Any delays can cause further damage to the vehicle, which can become very costly.

Cost of changing transmission fluid

While some manufacturers produce cars with sealed for life transmissions that never require changing the fluid or filters, some cars require a transmission fluid change every 40,000 miles.

It is important to note that there are filters and a pan gasket that need replacing too. The average cost of changing the transmission fluid starts at $300, depending on the make and model of the car.

4. Failing driveshaft

The driveshaft, as the name suggests, is a shaft that drives the car. It takes the power the engine produces and delivers it to the wheels of the vehicle.

Although the driveshaft will not fail as quickly as other parts, it can happen due to corrosion and spirited driving.

Signs of a failing driveshaft

A failing driveshaft will show some of the following signs:

  • Clunking, rattling, or squeaking noise from under the car
  • Shuddering when accelerating
  • Problems when turning
  • Increased vibrations while driving
  • Drivetrain or Powertrain Warning light

Cost of repairing a damaged driveshaft

As with other car parts, the cost of repairing a failing driveshaft will heavily depend on where you take your car for reparations.

A main dealer like Ford or Mercedes will quote you from $500 to $1200, while a local repair shop can do it for a little cheaper. However, it is always important to choose a qualified and knowledgeable person when repairing your car.

What should you do if you hear a clunking noise when driving?

If your car starts making unusual noises, you should drive it to a repair garage and have it inspected by a mechanic as soon as you can.

Troubleshooting on your own can be difficult, but you should pay attention to the area where the sound is coming from, and more importantly, when you can hear the sound. Before getting the car to the mechanic, try and replicate the sound as many times as possible.

This will help to identify the culprit a lot easier, saving you money and hassle!


How transmissions work

Drive Shaft

What is transmission fluid?