Subaru Outback Front and Rear Differential Noise Causes and Fixes

Do you hear loud noises any time you use to shift gears? Does your Subaru outback make annoying whining noises in the back? If that is the case then something is probably wrong with your rear differential.

The rear differential is responsible for taking power from the engine and splitting it up to both your drive wheels. This suggests that if one of the wheels begins to spin faster than the other, it can cause grinding or clunking noise from beneath your vehicle.

Some of the most effective ways to fix your Subaru outback rear differential noise are to replace the seal, lubricate the axle and replace broken spider gears and other internal parts of the rear differential.

There are several reasons why the Subaru outback makes rear differential noise some of the causes may include;

  • Inadequate differential fluid 
  • Overload during towing 
  • Faulty pinion gear bearing
  • Failure of the wheel bearing 

The rear differential is a complicated assembly consisting of gears, bearings, and assemblies.  So hearing strange noises from your Subaru outback rear differential is not only annoying but is also worrisome as the noise indicates an underlying problem.

Here are some of the possible noises you will hear from your vehicle and what they mean.

Howling or Whining Noise

You may hear a whine or howl noise when decelerating your vehicle. You may also hear some sound anytime you accelerate. This noise usually indicates a loose ring pinion gear. 

Rumbling or Clunking Sound 

You may hear this noise anytime you hit a corner. This noise suggests that something isn’t right with the spider or side gears. The noise may also be a sign of leaking fluid or broken gear. 

Clunking Noise 

You may hear this after you have traveled some few yards. This noise indicates a broken gear or pinion gear.

Also Read:

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Potential Causes of Subaru Outback Front and Rear Differential Noise 

Faulty Wheel Bearings 

A faulty wheel bearing may induce a humming noise in your Subaru outback. Some of the most common signs of a defective wheel bearing are the grinding or humming noise within the cabin from the direction of the affected wheel 

In other cases, the symptoms may include a knocking noise when you are cornering and vibrations in the steering wheel or the vehicle’s whole body.

The humming noise becomes louder when you drive faster. The entire weight of the vehicle lies on the bearings, this means there is so much force on the bearings as it also absorbs high radial forces. A failing bearing may not be able to support the gears properly. The bearings may wear out quickly depending on your driving habits, driving on uneven roads or potholes has a lot of negative impact on the bearings. 

Using the Wrong Oil Type 

Another reason why your rear differential may make noise is the use of the wrong oil type on your vehicle. You may discover oil spots under your vehicle around the differential housing, thus the wrong oil type causing leakages. The oil may not work as it should, which relates to it not being able to lubricate the spider gears, differential, and ring gears. Once this occurs it will lead to friction causing the differential, ring, and pinion to fail hence creating the noise.

Defective Wheel Balancing 

If you are hearing a loud noise on the rear of your Subaru outback it may be caused by the wheels. A defective wheel balancing can cause instability in the wheel’s logical path and thus leading to its vibrations. 

Lack of Oil

One of the common causes of differential rear noise in your Subaru outback is the lack of oil. The lack of oil can cause grinding noise when driving at high speed due to metals rubbing against each and the friction between them. 

In extreme cases, a lack of oil can cause the carrier to break or block the rear wheels. Several things can lead to low differential oil but the most common cause is worn out differential seal or a cracked housing that may lead to leakage of oil.

Deformed Tires 

Another cause of the noise in the rear of your Subaru outback is uneven tires. The tires may begin to scallop and stick poorly to the ground when driving at high speed hence causing the noise. In this kind of tire, wear dips are formed around the treads, this point out that the wheel is out of balance. It also indicates you need to replace worn-out shock absorbers.

Most of the tire wear is caused by improper wheel alignment, unbalanced wheels, and over-inflated or inflated tires.

Steps to Fix Your Subaru Outback Rear Differential Noise

Prepare Your  Vehicle 

You can get the vehicle ready by placing it on a jack stand and getting a wide catch pan to help drain the fluid. 

Refill the Differential Fluid 

The owner of the vehicle should follow the instructions in the manual to determine how often you need to change the differential fluid. If you have changed your differential for a long time, then it is time to drain the fluid and refill it with a fresh supply. This will help remedy the rear-end noise problems.

Replace the Seal 

Once you have drained the oil fluid and have detected the small metal piece, then you must replace the seal. You can do this by completely removing the cover and finding out if it has any defects.

If your vehicle is making an extremely loud whining noise, then replacing the seal is the only way out. Once you have replaced the seal the noise will stop. However, if you have a differential leak, replacing the seal will help stop the leak. To determine if there is a leak or not check out for any Brown fluid on the ground.

Test Drive Your Subaru Outback

In most instances replenishing the differential fluid or replacing the seal will considerably quiet the differential. Taking your Subaru outback for a test drive will help you determine if the differential noise had stopped or not. If the noise had disappeared then you have solved the issue. But in case the noise persists, then you need to visit the auto shop for a quick fix. It may be that other differential parts are faulty. 

Replace Broken Spider Gears and Other Inner Differential Components

If you realize any component is broken within the differential rear of your Subaru outback then it needs to be replaced urgently. These parts may include the pinion shaft, ring gear, bearings, or seals. This will effectively help remedy the differential noise issues. 

Clean the Housing of the Rear Differential 

Sometimes your rear differential gasket may be filled with dust and dirt. The accumulation of dirt and dust on the gasket may induce some weird noise. To clear out the dust and dirt use a brake cleaner and a clean throw rug to clean up the rear differentials.

Lubricate the Axle Shaft 

Applying gear oil on the rear axle and the steering axle will help lubricate these parts and make the gears rotate smoothly.


Ignoring rear differential noise can lead to major problems and cause irreversible damage to the ring and pinion. So you need to fix these problems urgently when you begin to hear rear differential noise in your vehicle. Fortunately enough we have discussed some of the best methods to help you fix your Subaru outback rear differential noise. However, it’s advisable to call up a professional mechanic to fix it if you can’t do it yourself. Also, ensure to lubricate the rear differential regularly.

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