How And Why You Need To Change Your Differential Fluid

A vehicles differential, or gear box, gears are surrounded by fluids that help keep them protected while the vehicle is in operation. To breakdown what the differential does easily, it basically assists the power in the engine to turn the rear wheels and lets the wheels turn at different speeds when necessary. As a car is driven, the differential fluid heats up and over time, breaks down to a point where a car will have metal to metal contact that stops the gears from being able to turn the wheels.

Surprisingly, with as much work as the differential is responsible for when it comes to ensuring the car can travel, many people have never heard of it and would have no clue as to where it is or what it does. For a great deal of people, they don’t even hear the word differential until they go in for an oil change and a mechanic tells them they may want to have their rear end serviced.


What Exactly Does a Differential Do?

You now know that the differential has something to do with engine power and turning wheels, but what is this part and how does it work?

Many individual gears work as one in the differential and they work to maintain the right tire speed when the car is driving directly down a straight roadway, but they also help adjust the speed of the wheels as the car goes around curves. There are times when wheels need to be at two different speeds to make sure the driver has good control of the car always. For instance, when a car is going around a sharp curve in the road, the inside wheels need to go a little slower than the outside wheels. The differential, and the gears and fluid surrounding them is what ensures the wheels will turn at the speeds they need to turn to offer the car maximum stability during a drive.

If you own a brand-new car and take it in for the first oil change between 3500 and 5000 miles, you will not hear about the differential. Once the car gets up to around 30,000 miles, then shops will start mentioning having the differential changed or serviced.



The Difference in Differentials

Differentials will vary in every car. This means some cars have them in the front and some in the rear and some even have them in more than one place altogether. For motor vehicle owners, this can be confusing, but let’s try to break it down.

Owners of rear wheel drive cars will find that their differential fluid is located at the rear of the car, which is why a mechanic will recommend having the rear end checked or having the rear end fluid changed.

Front wheel drive cars will have the differential in the front of the car. The difference in this is that with a front wheel drive vehicle, the differential is called the transaxle and it takes transmission fluid rather than separate, differential fluid. It works the same however and ensures the wheels turn. When a vehicle owner must get a repair shop to check their transmission fluid or change it out, they are essentially having their differential fluid checked or changed.

What about car owners who drive a 4WD? These have differentials as well, but unlike 2WD vehicles, a 4WD has three separate differentials that include one in the front as well as another in the center and one in the back as well. The one located in the center is commonly known as the transfer case and it has a job all its own. The center differential or transfer case is what fine tunes precisely how fast or slow the speed is on the rear wheels and front wheels.


Reasons for a Change

While mileage alone can be a legitimate reason to have the differential checked or have the fluid changed, there are also other reasons that may cause a change to be necessary long before the mileage even comes into play.

First, based on various serve recommendations, cars may need a regular differential service anywhere from 20,000 to 50,000 miles. This will, of course, depend on the type of car and what the manufacturer recommends. It is important to take time to read the handbook to your car because it will tell you when different services including oil changes, transmission changes or rear end servicing needs to be taken care of.

If you own a truck and do a lot of heavy hauling, it can cause those fluid temperatures to rise to levels that cause them to burn faster than they would under normal wear and tear, thus making it possible that the vehicle will need to be serviced sooner than the mileage recommendations.

People who own boats and make frequent visits to drop the boat from a truck to the water might find that water has seeped into the differential and when this happens, it can not only cause water to get into the fluid, but it can set the rear end up for rust. Whether it is water in the fluid or rust, it should be serviced quickly to prevent escalating damage to the vehicle.



While mileage and even water contamination can be valid reasons to have the differential checked or the fluid changed, did you know that the very sound of your car can be a good warning sign as well? If your car goes form quiet rides to sounding like a bear roaring in the woods, it may be a good time to have things checked out. Loud noise in the car could be many things, but often it is where the fluid has gotten low in the rear end and the gears are beginning to move against one another. Some people tend to ignore the noise, but when gears start sticking together, they can lock up and this can not only cause the car to become inoperable but imagine them locking up on the interstate and suddenly, the wheels don’t move. This can cause the car to crash and not only will you need to have it hauled from the roadway, but you will quite possibly find that you or someone else has bodily harm or that the crash causes a fatality. This is a preventable crash waiting for the vehicle owner to have the car serviced.


How Differential Fluid is Changed

Differential fluid can be changed in various ways depending on the vehicle as well as the tools the repair shop has available to change the fluid and refill the fluid. Some of the more modern shops will possibly own an extractor that will not only remove the old fluid, but it will also refill with new fluid. Older shops and those that don’t own an extractor machine will often pull the drain plug and let the fluid drain out slowly and then will manually refill the fluid once the old fluid is drained.

The mechanic will watch for metal shavings in the old fluid and will be able to either refill immediately with new fluid if no shavings are seen, or they can remove the cover and get everything nice and clean as new before refilling with new fluid. Metal shavings can cause the gears to mess up even when new fluid is put in, so if they can get those removed, the gears will move smoother.

Most vehicle owners strive to ensure regular maintenance is taken care of. This not only includes regular oil changes or tire rotations or even brake jobs but also includes having the differential checked and changed when needed. Think of it this way, having your rear end checked when needed might cost you up to $40 or so, but if you ignore it and fail to have it checked when needed or you don’t have the fluid changed, you could be looking at a service bill of more than $1800 to replace the differential. Save your money and keep your car running smoothly by having the differential checked and changed when needed.