Subaru Outback Rattling Coming From Behind: Causes + Diagnosis

Rattling Noise When Going Over Bumps

If you hear your Subaru Outback rattling when going over bumps, this sound could be caused by various issues, from minor to more serious. 

Here, we’ll explore the potential causes of the rattling sound in your car and offer possible solutions.

Subaru Outback Rattles from behind

The most common reason for a rattling noise when hitting bumps is a loose exhaust heat shield.

Rattles VS Clunks

If your Subaru Outback has a rattling noise, it rarely indicates a serious issue. While a clunking sound usually does.  A clunking noise will usually correspond with a suspension problem.

On the other hand, a rattling noise may not be felt in the steering wheel when going over a bump.

Subaru Outback Rattling Noise Common Causes

Exhaust Heat Shield(s)

Rattling Noise Coming from the Rear Causes

One of the most common causes of a rattling noise in the Subaru Outback is a loose exhaust heat shield. 

A heat shield’s job is to prevent heat from the hot exhaust from coming in contact with the car’s undercarriage.

Heat shields can be used at any point in the exhaust system to keep heat from radiating into the cabin or soaking into the engine.

When a heat shield becomes loose or damaged, it produces a rattling sound, which can increase as your Subaru Outback accelerate or as the engine speed changes.

Loose exhaust heat shields affect every type of vehicle. The solution to this issue is to have your Outback’s heat shield reattached or replaced.

Exhaust Hangars

One other potential cause of a rattling sound could be loose exhaust hangers. Rubber hangers support your Outback’s exhaust system.

If they become loose or damaged, they can cause the exhaust system to vibrate with the engine, which generates a rattling or clunking noise. 

In this scenario, the rubber hangers must be reattached or replaced.

A good exhaust shop can diagnose and repair your Outback’s heat shield’s fast.

Catalytic Converter

Another common cause of a rattling sound coming from the Subaru Outback is an internal rattle inside the catalytic converter.

If your car’s catalytic converter is failing, it may get the P0420 OBD II code, which indicates that the catalytic converter is losing efficiency.

Suspension Components

Shock Vs. Strut

Another possible cause of the rattling noise could be damaged suspension components. If your Outback has bad shocks or struts, or other suspension parts are worn out or damaged, it can cause a rattling sound while driving over bumps. 

Sway bar bushings are also possible causes of a rattling noise. These bushings act like a bridge between the sway bar and the frame of the car and help to reduce vibration and noise.

When sway bar bushings become worn out or damaged, they can cause a rattling sound. Almost every modern vehicle uses a sway bar (including the Subaru Outback). 


Lastly, it is possible that smaller components like loose license plates or other miscellaneous items inside or outside of the vehicle are contributing to the rattling when going over bumps noise.

Almost anything can get loose and cause your Outback to start rattling. Here are some other items that can cause a rattling sound.

  • Bad sway bar bushings– Sway bar bushings are a common issue that can cause a rattling noise.  It’s usually more of a squeaking sound.  
  • Worn out shock absorbers/struts–  A worn out shock or strut can cause a rattling sound.  Take a look at your Outback’s shock bushings and verify they are in good shape.
  • License Plate– A loose license plate can cause a rattling sound.  A couple of generations ago, you’d often find an empty pack of cigarettes behind the license plate to keep it from rattling.
  • Loose Brake Discs– If a disc isn’t’ attached to a caliper, it’ll rattle.  The rattling sound will go away when you push the brake pedal, and the distance between the caliper and pad decreases.


P0446 Definition

This process works better if you have a partner to listen for the clunking or rattling sound.

  1. Start your Outback’s engine and keep the engine in park or neutral.
  2. Rev the engine up and down.  Hold it at different RPM levels and listen.
  3. If you hear a rattling sound, it’s likely an exhaust component since only the engine is moving.
  4. Shut the engine off.
  5. If it’s not rattling when you rev the engine, try rocking the car up and down and from side to side.
  6. If you hear the rattling noise, it’s likely a suspension related issue.


Overall, it is important to identify and solve rattling sound issues before they cause further damage to the car. Do not take the rattling noise lightly, as it can indicate your Subaru Outback has a serious suspension problem. 

By identifying the problem early and taking the necessary steps to fix it, you can avoid further issues in the future. In conclusion, if you experience rattling noises while driving over bumps, be sure to have your car inspected by a certified mechanic to diagnose the issue and correct it promptly.