What causes rear knocking noise at low speed?

There are several different reasons why a driver may hear rear-knocking noises while driving at low speeds. Here is a list of possibilities.

  • Suspension Problems
  • Brake Problems
  • Rear Differential Issues
  • Engine Connecting Rods

Some of these problems may be a simple fix, while others may be more complex. Whatever the situation, you may need a mechanic to inspect the rear of your vehicle.

Specifically, if you do not want these problems to escalate into much bigger and more costly repairs.

How to fix rear knocks?

The repairs for these types of issues usually vary on a case-by-case basis. This is why you may need a mechanic to inspect the rear of your vehicle first. And once the problem has been identified, the repairs can be made.

With that being said, here are 3 possible causes and the repairs that are normally recommended as the fix.

1. Suspension Problems

Whenever the components begin to age, there is a higher likelihood that the noise that you hear at low speeds may be related to suspension problems.

Specifically, those that arise when the components are rubbing together and causing the parts to knock together loudly. In these situations, these components may not be properly lubricated.

Or, on the flip side, the shocks and struts may be worn due to wear and tear.

Fix: Normally, the cause of this type of problem is a lack of lubrication in the suspension components. Therefore, if you want these noises to go away, these components will need to be properly lubricated.

Or, if the shocks and struts are bad, they should be replaced to stop the noises from the rear of the vehicle.

2. Brake Problems

When a mechanic inspects the brakes in these situations, they may identify one of several problems with the brakes on the car. For instance, the brake pads’ calipers are not lubricated enough or the brake pads are worn down due to excessive wear and tear.

Fix: To fix brake problems, you may need to install new brake pads. Or, you may need to pay for services to lubricate the brake calipers properly.

3. Rear Differential Problems

Noises caused by rear differential problems are often caused by poorly lubricated components. When this happens, the noises that the driver hears are often coming from the gears grinding and knocking.

Fix: To fix a rear differential problem, the components will need to be lubricated.

How much do repairs cost?

Depending on the problem that has been identified, the costs will also differ from one repair job to another. So, here is what you can expect to pay.

Suspension costs

The average cost of fixing suspension problems can range from around $100 for suspension lubrication services. Or, if you are paying for suspension components like shocks and struts to be replaced, you may pay between $450 to $1,100 as a ballpark estimate. This is because there are several factors to consider including the following:

  • Make, model, and year of the vehicle
  • Cost per axle
  • Dealership versus Local auto shop
  • Location

Brake Problems:

If the brake problems that exists is related to problems with bad brake pads, you may need to shop around to save on the cost. For instance, if you are buying OEM brake pads, the cost for each axle can start at about $150 to $300 in total on average.

Rear Differential Problems

The cost of rear differential problems can range from light repairs to extensive work that needs to be done. And depending on the make and model of your vehicle, here are some basic amounts that you may be required to pay.

  • light repair jobs – $200 to $400, depending on the make and model of your vehicle
  • extensive damage to the differential – $400 to $800 or more


As you can see, there are three major causes why car knocks in reverse at low speeds. These alongside engine connecting rod issues can lead to knocking sounds.

Although bad engine rods are a rare cause, these parts are expensive to repair. The average costs of fixing are between $1200 and $4000 for the parts and $2000 to $2500 for the labor because removing and dissembling the engine takes some time and also the mechanic needs to put a lot of effort into it.

Therefore, if you want to know what is happening to your vehicle, you will most likely need a mechanic to check the vehicle out. A professional mechanic will know what to look for when they are assessing these issues.

And once they have identified the problem, they can provide a clearer understanding of the source of these noises, the repairs that need to be done, and the cost that is associated with the parts and labor.

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