Car Oils And Fluids

Can Changing Transmission Fluid Be Bad For Your Transmission?

Mike Cross
Updated Oct 30, 2021

Your car’s transmission is responsible for taking the power from the engine and transfer it down to the wheels. It may sound like a simple process, but modern transmissions are a complex piece of modern engineering.

Much like your engine needs oil to help lubricate and keep the temperature down, so your car’s transmission. Without some sort of lubricate to stop metal-on-metal contact, a vehicle's transmission would end up eating itself in a matter of miles.

Several factors can play a role in knowing when your transmission fluid needs to be changed. But can changing your transmission fluid be a bad thing? How often should your transmission fluid be changed?

We will answer these and many others related to keeping your gearbox running at peak efficiency. This way, you can make a smart decision instead of just guessing whether or not you should change the fluid?

Can changing transmission fluid be bad for your transmission?

Can Changing The Transmission Fluid Be Bad For A Car?

Changing the transmission fluid on a car can be both a good and bad thing. This section will expand on why a transmission fluid change is beneficial or potentially cause more damage.

You will hear a lot of people mention, the classic “if it ain’t broke, don’t fix it”. While this may be true in some cases, it can spark a debate in the car community. When talking about transmission fluid, higher mileage vehicles that have never had their transmission oil changed, should be left as it.

Over time, automatic transmission's clutches begin to wear out. The material is then deposited in the fluid, increasing the overall viscosity of the fluid. Thicker fluid can help provide the additional pressure needed on worn-out clutches. By putting in new transmission fluid on an old car, you can run the risk of creating more damage, or even worse, having the gearbox completely fail.

On the other hand, if your vehicle has lower mileage and you have maintained the gearbox regularly, doing a flush of the transmission fluid can be beneficial. It can help get any debris or contaminants out and keep everything in tip-top condition.

As you can see, the mileage and condition of your car will play a crucial role in telling you if you should change the transmission fluid. If you have an older vehicle that is not showing any signs of gear slippage or hesitation when shifting, our advice is to leave it as it. You may end up doing more harm than good.

What is transmission fluid?

Much like engine oil, transmission fluid is made from the same basic ingredient, crude oil. The crude oil is then refined and has several other additives to make it the right viscosity.

Depending on what it is used for, the fluid must have a certain viscosity or thickness. If it is too thick, it won’t reach all the nooks and crannies of the transmission. On the other hand, if the fluid is too thin, it will not provide the proper amount of protection when the different gears come in contact with one another.

Just like Goldielocks and the three little bears, the fluid must be just right for your gearbox.

How to Know When to Change?

The best way to know if your transmission fluid is needing to be changed or not is to look at it. It should be a reddish color, and if it still is, then it is probably good.

If it is black, then it is burnt and needs replaced. If it is starting to get dark, but still has some red tinge to it, then that is the perfect time to replace it.

How often should transmission fluid be changed?

This is a question that is often disputed. Some automakers claim their transmission fluid will never need changing. While others say it should be done as early as 30,000 miles or as late as 60,000 miles.

Any experienced mechanic will tell you that there is no such thing as a lifetime gearbox oil. That is of course if you want to make your car last past its factory warranty.

Every transmission is different, therefore its fluid should be changed at different intervals. Your style of driving will also play a role as to when the oil should be changed.

The best thing is to do your homework. First off, check your owner's manual. Secondly, check forums online. Owners with the same make and model you have will be the biggest help as to how often the transmission fluid be changed.

Options for Replacing

You actually have a couple of options when it comes to changing transmission fluid, and that is having your transmission completely flushed or just changed.

This is where the real debate lies for if it is bad for your vehicle or not.

Transmission change

A transmission fluid change is the simpler of the two options. With a transmission fluid change, the transmission fluid is drained out of the pan, and the filter is changed. The transmission pan actually doesn’t hold that much fluid in it tough.

On most vehicles, it holds about half the fluid, but the other half is still inside the torque converter and lines. When doing a transmission change, you are only replacing about half of the old fluid. This will get important later on explaining why transmission fluid changes might be bad.

Transmission Flush

A transmission flush, on the other hand, removes all the fluid or tries its best too. The pan is drained, and then a machine is hooked up to the cooler line, and it pumps out all the rest of the fluid.

This removes 95% of the fluid and also the gunk that comes with it. Then the new fluid is put in. This way makes the fluid brand new which logically seems better, but is it?

How Do I Know It’s Time To Change The Fluid In My Transmission?

Why can Transmission Flush be Bad?

Why can transmission flush be bad
Why can transmission flush be bad?

If you are reading this, then you have probably heard stories where people have had their transmission flushed, and then it stopped working.

If people didn’t have problems with their transmission after fluid changes, then there wouldn’t be the question of if a transmission fluid change is bad or not. So, now we will get into why it might be bad now that you understand the two ways of changing transmission fluid.

When transmission fluid gets old gunk builds up in it. Pieces of the gears break down and get in the material. These extra pieces get between the gears in the gearbox and make gaps. As long as the metal is there, then the gears will work fine, but if they are removed, then you might start getting slipping.

This is why some people think that flushing the transmission and removing all the gunk can be bad and hurt it and why you hear stories of people getting flushes have their transmission stop working.

Even if you think you may never have to change your transmission fluid, your car’s gearbox will let you know when it is time.

Here are some of the most common signs that it may be time to change the transmission fluid. Remember, these are just some of the most common and are not the only ones.

Check the fluid

This may sound easy, but on newer models, checking the transmission fluid may a difficult task. As we previously mentioned, some auto manufacturers do not want you to change the transmission fluid as they think it is not needed.

Some older vehicles came with a dipstick for the transmission, just like the one for the engine oil. Newer vehicles require a mechanic to take out the fill plug and check it manually.

Is the Flush to Blame?

Is, the transmission fluid flush really to blame though? The answer is no; the blame is that the transmission wasn’t taken proper care of to start with.

If you take proper care of your transmission and have the fluid changed or flushed regularly, then you won’t have to worry about components breaking off into the fluid and for gaps occurring. Proper transmission care will keep your transmission working correctly.

Should You Get a Flush or Change?

With that said, should you get a transmission fluid flush or just a change? Well, the answer is it depends.

If the car has always been yours, then you can get the transmission fluid flushed and not have to worry about anything because you know how often and how well you took care of it.

However, if you have not always had the vehicle and it has a lot of miles on it, then you should probably just start having the transmission fluid changed when it is needed.

That way you don’t have to worry about the free metal being removed. This will make sure your transmission will keep working, even if it won’t last as long as a properly taken care of transmission.

The Key

The key thing with your transmission though, and making sure a flush won’t hurt your transmission is to stay on top of the fluid that is in it. You want to care for your transmission from the life of it, so you don’t have to worry about pieces breaking off.

You can do this by having the fluid changed based on what your mechanic recommends and having it flushed every other time or so.

Also, you need to stay on top of your fluid level and make sure it isn’t getting old and burnt. Some people will say don’t bother it till you have problems, but once you have problems fixing them is expensive.


So, to wrap things up is changing the transmission fluid bad for your transmission? The answer is no, changing the fluid is never bad for your transmission. A change only removes about half the liquid anyways.

Is a transmission flush bad for your transmission then? Well, the answer to that is also no. A flush is never the thing that is bad. If your transmission is damaged already though, then a flush can cause the problems to start showing, but the thing that was bad was the improper care of the transmission, to begin with.

Should you have your fluid flushed? The answer to that is it depends. If you have always had the car and took care of the transmission, then a flush is fine.

If you haven’t always had the vehicle through and it has a lot of miles, then I would just stick with transmission fluid changes, that way you don’t have to worry about possible problems showing up.

Now you know enough though to make an informed decision on if a transmission flush or change is right for you and you also know the answer to the question of is a transmission fluid change bad for your transmission.

Mike Cross
Life is too short to drive with stock audio

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