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Transmission Fluid Change VS. Flush – What’s The Difference?

Transmission Fluid Change VS. Flush – What’s The Difference?

If you have a car with an automatic transmission, you might be due for some maintenance that you were not even aware of. Most everyone who owns a car knows that they have to change their engine oil, but did you know that you also have to regularly change your transmission fluid as well? This is crucial maintenance that must be performed to extend the life of your transmission. Without this service being done, the fluid in your transmission gets old and loses its cooling and lubricating properties. That spells bad news for your transmission!

There is actually more than one way to perform this service. There is the traditional transmission fluid change, but there is also a transmission flush that accomplishes the same end goal. How do you know which one is right for you, and can you perform this service yourself? Keep reading because we will explain the difference between the two as well as offer some tips for those of you who like to DIY all things automotive.

What Is the Difference Between a Transmission Fluid Change and a Transmission Flush?

To get a better understanding of the difference between these two methods, it will help to have an understanding of what each of these methods is. Let’s take a look at each method separately, then we’ll dive into the key differences between the two as well as some debate over which is better.

Traditional Fluid Change

Most of you are probably familiar with how an engine oil change works. Simply remove the drain plug, let the old oil drain out, replace the filter, and then refill with new oil. Pretty simple, right? Well, a transmission fluid change is pretty much the same concept. Except not all automatic transmissions have drain plugs. In fact, most of them do not. So in order to change the fluid, the transmission pan must be removed so that the old fluid can drain out.

With the pan removed, the transmission filter or screen can be replaced. The pan is then reattached using a new pan gasket, and the transmission can be refilled with new automatic transmission fluid. This can be quite a messy process as the fluid drains pretty erratically when the pan is removed. We’ll provide some tips for making this less messy in the next section. But, as for the basics of the fluid change itself, that’s it. Now let’s take a look at the flushing method.

Automatic Transmission Flush

This is the method that most dealerships and repair shops use today because it requires much less manual effort. The flushing method entails hooking up a machine to the car’s transmission and letting it do all the work. The machine either acts like a vacuum and sucks out all the old fluid or pumps in new fluid as the transmission itself pumps out all the old fluid. Either way, the fluid is removed through the use of force or pressure and the transmission is refilled during the same process.

Flushing is typically faster and less messy than a traditional change. However, there is much debate about which method is better for your transmission. There are pros and cons to both methods, and mechanics still disagree about which method you should ultimately choose. Even with this debate, there are certain aspects of each that most everyone agrees on and you can use these facts to help you decide which is right for your car. Let’s now examine these differences in more detail.

Let’s first talk about the removal of the old fluid. A traditional change does not actually remove all the old fluid from the system. At least 30% or more of the fluid remains in the torque converter and other parts of the transmission. Gravity is simply not enough to remove it because it sits inside other internal parts. A transmission fluid flush, however, uses pressure to push all the old transmission fluid out of the system as it is refilled with new fluid. It is more of a fluid exchange than a drain and refill.

For this reason, many mechanics recommend performing a second fluid change within 10,000 miles of the first. This helps to make sure that the fluid and contaminants are fully removed from the transmission and it is refilled with fresh fluid. If a flush is performed, there is no need to perform a second one so soon. One is enough to fully refill the transmission with new transmission fluid, although remember that you do need to perform this service at your manufacturer’s recommended interval.

Another big point of debate between these two methods is the amount of stress that each places on your transmission system. With a regular change, there is little to no stress placed on the system. The fluid simply drains out due to gravity, and there is no pressure present to force tiny particles or metal shavings into places they should not go.

A flush, on the other hand, uses pressure to force the fluid out of the system. Many people argue that this pressure can force tiny particles and contaminants into parts of the transmission where they should not be. This can cause terrible consequences like improper shifting, overheating, slipping, or even total failure. Many of these people also argue that flushes can cause a transmission to leak because the seals inside the transmission are not made to withstand that much pressure. This can cause the seals to break or burst and fluid to leak. Conversely, those who are fans of the transmission flush contend that the pressure actually cleans the internal parts of the transmission.

How to Change Transmission Fluid

If you are the DIY type who likes to do all your own car maintenance, then you might be wondering how you can change the fluid in your transmission on your own. Luckily, it’s not as difficult as it sounds. The exact process depends on whether you are planning to do a simple change or a flush. We’ll provide step-by-step instructions for both methods here.

Standard Fluid Change

Before you start, make sure to read through all the steps and be certain that you possess the tools and skills needed to perform this transmission service. Otherwise, you might be left in quite a mess as you could do permanent damage to your vehicle’s transmission.

Before you get started, be sure your car is supported with jack stands. Never get under a car that is not properly supported! Once you are certain it is safe, then climb underneath and locate the pan on the bottom of the transmission. Look and see if it has a drain plug. If it does, then your job just got much easier! Simply remove the drain plug and let the fluid drain out into a pan or bucket.

If there is no drain plug, then things will have to get a little messier. You’ll need to remove the pan so that the fluid can drain. Remove the screws from one side of the pan first. Be ready as fluid will start to leak out once you start removing screws. Once you have screws removed from one side, loosen the screws from the other side so that you can slightly tilt the pan down and allow the fluid to drain out. Once the drainage slows, go ahead and remove the screws from the other side so that the pan can be removed. Watch out as this can get quite messy!

If your transmission has a replaceable filter, then go ahead and replace it with a new filter. Now, you’ll need to remove the old gasket from the mating surfaces on the pan and the bottom of the transmission itself. Make sure to remove all the pieces and get the surfaces as clean as possible. Otherwise, you will not get a good seal and fluid will leak after you replace the pan. Go ahead and install the new gasket, set the pan into place, and hand thread the screws back into the pan. Before tightening them, refer to your owner’s manual or a repair manual for the proper tightening sequence and torque specs.

Once you have the pan replaced, you will need to fill the transmission with new fluid. Since all the old fluid will not have drained out of the system, only pour in about 60% of the fluid capacity. Check the fluid level, and then top it off if necessary. Congratulations, you just changed your transmission fluid! If you have decided to perform a fluid flush instead, then keep reading for instructions.

Fluid Flush

First, you will need to locate the transmission cooler lines where they enter and exit the radiator. It will likely be somewhere close to where your coolant lines run into and out of your radiator. Remove the line that runs out of the transmission and place it into a bucket. Go ahead and place a funnel into the filler neck and be prepared to start pouring new fluid into the funnel. The next steps go quickly, so make sure you are ready.

Start the engine of the car, and old fluid will begin pumping out of the cooler line and into your bucket. At the same time, go ahead and start pouring new fluid into your funnel. Make sure that you do not run it dry as that could be detrimental to your transmission. Once you’ve poured about 70% of the fluid capacity back into the funnel, go ahead and shut off the engine. Replace the transmission cooler line. Check the fluid level and top off if necessary. You just performed a transmission fluid flush on your vehicle!

While this might not seem that difficult for some folks, it probably seems overwhelming for many people. If this all seems like too much, then don’t worry! You do have other options. Instead of going through all the trouble of changing fluid, spilling it everywhere, and possibly ruining your car, just sell your car to Auto Wranglers and use the money to buy one that does not need a transmission service. This requires almost no effort on your part. They will come to you to pick up the vehicle, provide free towing, and pay you cash! It couldn’t be easier!

How to Check Transmission Fluid

Transmission Fluid Change VS. Flush – What’s The Difference?

Just like with the engine oil, your transmission has a dipstick that you will use to check the fluid level. However, unlike with the oil, your car needs to be at normal operating temperature before checking the level. Start your engine and let your car warm up to full temperature. Next, shift through the gears in your transmission. Go to reverse, then neutral, then to drive, and then back to park. This will help to properly disperse the fluid through all the moving parts of the transmission so that you will get an accurate reading. Next, leave the car running and pull out the dipstick to check the level. If it is low, then top it off with some fresh fluid. Also, keep an eye on the color of the fluid when you check it. It should be a bright reddish pink color. If it is brown or dark red, then it’s time for a change!

When to Change Transmission Fluid

As mentioned above, if your fluid looks dark or dirty, then it’s definitely time for a change! The correct answer to this question though depends on your specific vehicle. You should refer to your owner’s manual for the proper interval for changing the fluid in your transmission. Some vehicles have service intervals every 40,000 miles for the transmission while others can go 100,000 miles before they require a transmission service. Following the manufacturer’s recommendation for your specific vehicle will help ensure the proper operation of your transmission for years to come.

If you have a vehicle that requires more frequent transmission flushes, then don’t worry! Thankfully, this is not an extremely expensive service. The cost of a transmission flush usually ranges anywhere from $150 – $400. Compared to transmission repairs or rebuilds which usually average $1,000 – $3,000, this service is cheap insurance to keep your car running reliably for years to come.

How Much is Transmission Fluid

If you are planning to change your own transmission fluid, you might be wondering how much it’s going to cost you. The cost of fluid varies widely depending on what type of fluid your car requires. Automatic transmission fluid, or ATF, comes in several different varieties. There is Dexron fluid, Mercon fluid, fully synthetic varieties, and a few others. Make sure that you purchase the specific type that your car requires as using the wrong kind of fluid can have bad consequences and cause major transmission problems. On average, a quart of fluid generally runs about $6 like this Valvoline fluid here on Amazon. You might find some that are more expensive, but that would typically be for higher end vehicles.


Transmissions are complex pieces of machinery that must be maintained properly to stay in good working condition. The fluid must be changed through either a fluid change or fluid flush. After reading this article, you should know the key differences between the two as well as how to perform each on your own.

If you’ve decided that doing your own transmission service is just too complicated, then take the easy way out and call Auto Wranglers. We buy cars nationwide, so no matter where you are located in the country, we will come to you and pick up your car. Plus, we always provide free towing and pay you in cash. If this sounds better than getting covered in transmission fluid when you drop that pan, then contact us today to get your instant free quote. You’ll have cash in your pocket in a day or two, and you can be cruising around in a new ride that doesn’t need any kind of service.