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How Do I Check for Differential Leaks and Change the Oil?

Technical  ·  October 7, 2021

How Do I Check for Differential Leaks and Change the Oil?

Keeping a car well maintained is challenging, there's no question about that. It is especially true when it comes to dealing with leaks. Sometimes, a leak that is not immediately fixed can lead to catastrophic results. Other times, the 'leak' that you're freaking out about might not be a leak at all but just harmless condensation and water dripping under the car.

One leak that you need to be watchful about is one that comes from your car's differential.

What Is a Car Differential?

Let’s address this obvious question first. An automotive differential is what allows your car’s tyres to rotate at different speeds, especially around corners.

You see, if your wheels all rotated at the same speeds when you turn a corner, you'd lose traction. That's because the inner wheel must travel a shorter distance than the outer wheel. Without enough traction, you'd end up damaging your tyres, the handling would become unstable, and you could put too much strain on your drivetrain. All these are not good for your car.  

To deal with this problem, engineers created the automotive differential. Simply put, inside the differential are a bunch of gears designed to help the inner and outer wheels rotate at the right speeds, allowing you to handle corners successfully.

As you might have guessed, just like anything else in your car with gears and moving parts, there are oils or fluids involved.

What Are Differential Oils or Fluids?

Differential oil or fluid keeps all those moving parts lubricated. This oil tends to be thicker than the engine oil that you might deal with more regularly. That's because differential oil is designed to perform well under high pressure and not in high temperatures like in the case of engine oils.

Despite this thickness, differential oils and liquids can sometimes leak out, and when that happens, it’s clearly bad news.

How to spot differential leaks

Now we come to the fun part - Spot the Diff! 

Spotting the differential leaks, that is. Trust me, everything you've just read above will come in handy soon enough.

1. Check your parking ground

Personally, my favourite way of noticing leaks in my car is to look at the ground where it was parked overnight. As you back your car out in the morning to leave for work, pay attention to your parking spot to look for puddles or patches that don't belong there. As mentioned earlier, some of it may be harmless condensation. If you notice some fluids that weren't there before, it's worth taking a closer look.

2. Smell leaked fluids

Look at the fluids on the ground, touch it a little, and give it a little sniff. It might sound like an odd bit of advice but, trust me, it's the quickest trick there is. You see, differential oils or fluids have a unique smell. If you've done this enough, you should be able to tell it apart from the smell of engine oils or any other fluid.

3. Notice the location 

Another hint is the location of the leak. Look at where those fluids are located on the ground. Are they towards the front or the back of where your car was parked? If it was towards the rear, that is another suggestion that the leaking fluid comes from your differential.

4. Observe its viscosity 

As mentioned earlier, differential oils are thicker than engine oils or other lubricants. This, in itself, may help you narrow down and identify whether you're dealing with a differential leak.

5. Try to sense changes in your car’s performance

You can also observe your car's performance and use your senses to diagnose transmission issues. Sometimes, a leaking differential shows itself when you notice an unusual increase in braking distance. Or you may even hear a strange noise coming from the brakes in the back whenever you're trying to slow down.

Once these hints are clear to you, it's time to dig deeper and check for those differential leaks up-close. You should know that sometimes, those leaks aren't located at the car's differential itself. Yeah, odd. Instead, some of the seals might have failed, allowing differential fluid to flow elsewhere like the brake assembly.

If you suspect that your differential may be leaking but prefer not to deal with it yourself, you can always head to your preferred mechanic or workshop. If you don’t have a go-to mechanic, you can search for one via this directory, and don’t forget to specify your area. I'm a big believer in leaving specific problems like differential leaks up to the professionals. As an added benefit, you could use it as a learning experience, as most mechanics are more than happy to show you how they work on your vehicle.

How & When Do You Change Differential Oil?

The fluid in your car's differential, needs changing just like engine oil and other fluids. Don’t forget that a differential has lots of metal parts always moving against one another. Over time, those differential gears and moving parts could wear out and lead to costly repairs if you don’t change the fluid regularly.

When to change differential fluid

The best way to know when to change your differential oil is to refer to your car's manual. In there, you should see the manufacturer's recommendation for the differential oil change interval, either after a certain amount of time or after a specific distance travelled. 

If you're unsure about this, talk to your mechanic the next time you take your car in for regular maintenance. While you have the vehicle in the shop, you may as well get your differential checked.

How to change differential fluid, DIY steps

If you prefer to do it yourself, here are the basic steps:

1. Elevate your car on jacks or ramps. Your first task is to find the drain bolt for your differential, open it to drain the differential oil into a container.

2. Completely drain the differential oil. Once that’s done, put the drain bolt back and wipe away any spills.

3. Remove the oil-fill bolt or plug. Fill in the correct type of differential oil for your car. Again, details of this should be provided in your car owner's manual.

4. Fill in as much differential oil as the manual recommends. Replace the fill hole's bolt. Make sure you wipe everything clean, so there's no oil anywhere on the differential's casing.

And you're done!

Did you find this article helpful? Check out for more of these from CarPart Australia’s blog section. You may also want to try the many features on the website, including the Parts Request function to help you locate parts, like a car differential. It’s free to use, so why don’t you request a car part now!

By Ray Hasbollah

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