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How & Why to Change Your Differential Oil

Changing the differential oil on your vehicle isn’t something that comes across everyone’s mind, but it should. If you use your truck or RV to tow things regularly, it’s a vital step toward keeping your vehicle in good order. 

Going through the steps to change your differential oil from time to time isn’t much harder than the process of changing your engine oil, but it’s just as important. If you don’t know how to do it, you’ve come to the right place. Read on to learn more. 

What Is Differential Oil?

Just as your engine needs oil to keep all of its moving parts protected from excess heat and friction, your differential needs oil to allow the gears to move without hindrance. A “differential” is that big compartment on the rear axle of your vehicle. 

Inside that compartment, you’ll find all of the parts that work together to transfer engine power to your rear axle. In short, the differential houses all the contraptions that give your back wheels power. Differential oil goes inside of the compartment to keep all the parts well lubricated. 

How To Change Diff Oil

How Often Does Differential Fluid Need to Be Changed?

Your vehicle’s differential fluid doesn’t need changing nearly as often as your engine’s oil. In general, you should change it every 30,000 to 60,000 miles. However, this depends on how much work your car does on and off the road. If you push it particularly hard, change it every 15,000 miles. 

How to Change Your Differential Oil

First, you should know that you might face two situations when you get down to look at your setup. Your differential cover may have a drain plug. If it does, the process is a little easier to complete. If you have a differential casing that does not have a drain plug, you have a few more steps to run through to complete the job. Check out how to do it based on your setup. 

Know Before You Go: Before you hit the road, find out What You Need to Know About Your Front Differential.

Under a car close up on differential
Ensure you are safe and sound on the road by regularly maintaining your differential oil.

Drain Plug Differential

First, we’ll go over the steps of changing your oil if you have a drain plug on your differential casing.

Clean Around Drain & Fill

On a drain plug setup, you will have a fill plug somewhere on the side or top of the casing. You will also have a drain at the bottom. Take the fill plug out first, and clean it and the area around it. Then screw the fill plug back in just a little, so you won’t get any stray particles in your differential while changing the fluid. 

Open Fill Plug First Drain Plug Second

Next, place an oil pan underneath the differential to prevent spilling oil everywhere. Slowly loosen the drain plug until it comes free from the housing. Oil will begin to spill from the hole into your pan. 

Mechanic repairing vehicle differential
Prevent excess heat and friction in your differential by changing the oil.

Drain Differential Completely & Torque Drain Plug

Then, let the oil drain completely from the differential. Give it some time — around 5 to 10 minutes. After the oil drains entirely from the casing, close the plug. Torque the drain plug to the proper setting. Now, you can start refilling the differential with clean oil. 

Fill Differential & Reinstall Fill Plug

Make sure you have the right supplies before you get to this point because you can’t drive your truck to the store to get them now. With the correct type of oil, start filling your differential from the fill hole. Keep pumping oil into the housing until it starts to spill out from the fill hole. Then, screw the fill plug back into place, and you’re done. 

Pro Tip: Get the inside scoop on RV Oil Changes: What Every RV Owner Needs to Know.

Closed-Case Differential

If you don’t have a drain plug on your differential, the oil-changing process changes slightly. Here are the steps if you have a closed case.

Open Fill Plug First

On a closed-case differential, you’ll start by opening the fill plug. Take it out, and clean it and the surrounding area. Then screw it back in just a little to protect from contamination. 

Loosen Differential Bolts

Now, without a drain plug, the process shifts a bit. Loosen the bolts around the outside rim of your differential and place an oil pan underneath. Then remove all of the bolts except the top center one, as it will provide needed stability while draining it. 

Woman under car replacing differential oil
By following a few simple steps, you can change your differential oil by yourself.

Drain Differential & Remove Cover

Take a flathead screwdriver and gingerly use it to crack the seal on the housing. Once you open the seal, the fluid will begin running out. Ensure you’ve placed your oil pan. Once the differential oil has finished draining, remove the housing cover. 

Clean Cover and Inside Housing

Once you have removed the casing, you have to clean it thoroughly. Clean the parts that will be married by the gasket when you replace the cover. Use a plastic paint scraper to remove any pieces of the old gasket that remain. Take care not to scratch any of the surfaces, as they need to be smooth to function properly. 

Mechanic fixing differential oil under car
Change your differential oil roughly every 30,000 to 60,000 miles.

Install Gasket/Gasket Material

Once you properly clean the cover and the marrying part of the differential housing, you can start laying down the gasket. If you have a ready-made gasket, just put it in place. If you have a gasket sealing gel, place the goo along the middle of the marrying area in a continuous bead around the whole piece. 

Then let it sit for about 15 minutes, so it gets a little tacky. Once tacky, place it back onto the differential. Hand-tighten the bolts until you see a little bit of the gasket sealant pushing out on the edges. Then let it sit again for about an hour so the gasket has time to take shape. 

Tighten Differential Bolts

After you set the gasket, tighten the differential bolts to the specified torque with a proper torque wrench. If you’re not sure how to use this type of wrench, a quick YouTube search will fill you in on the details. 

Fill Differential & Reinstall Fill Plug

Now refill the differential oil and reinstall the fill plug. Check over your work to make sure you didn’t miss any bolts and you’re finished. 

Pro Tip: Uncover the truth about How Often You Should Really Check Your Oil?


Why Change Your Differential Oil?

It’s important to change your differential oil so you don’t run the risk of blowing out your rear differential. Your vehicle won’t do you much good without power to the rear axle. You’d probably be better off getting your hands dirty from time to time instead of ignoring the issue and hoping for the best. You can easily do this yourself by following these steps. Or you may prefer to take it to the mechanic. Either way, you want to keep your car in tip-top shape. 

So, what kind of differential setup does your truck or RV sport?  Tell us in the comments!

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About Tom Morton

Tom, a Pacific Northwest native, is our technical genius. Born in Washington and raised in Alaska before settling in Michigan. He's the man who keeps our operation running, both figuratively and literally.

With a background in Electrical Engineering, Tom specializes in RV solar systems and lithium batteries. He made history as the first documented individual to use a Tesla battery module as an RV battery. Tom has personally assisted countless RVers with system installations and has educated thousands more through his videos and articles.

Cinematography is another of Tom's passions, showcased in his work on the Go North series. You can see his camera skills on display in The RVers TV show on Discovery Channel and PBS where he also stars as a co-host.

Tom's mechanical expertise extends beyond RVs to boats, planes, and all things mechanical. He's renowned for taking on maintenance and repair projects single-handedly and is often spotted underneath RVs, making him the technical backbone of our endeavors.

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