Transmission flush vs Fluid Change

When it comes to servicing your transmission, there are two main options: a transmission flush or a fluid change. Both of these services are important for keeping your transmission running smoothly, but they do have some key differences. In this article, we’ll take a look at the pros and cons of each service so you can make the best decision for your vehicle.

Transmission flush vs Fluid Change

What is Transmission Fluid

Transmission flush vs Fluid Change

Transmission fluid is a type of lubricant used in newer vehicles to make the gears shift smoothly. When it begins to burn, transmission fluid turns into sludge, which can cause serious problems for your car’s transmission. If you are experiencing any of these symptoms, it might be time to flush your cooling system and change you transmission fluid.

Symptoms the ATF is wore out

Transmission flush vs Fluid Change

The Automatic Transmission Fluid (ATF) is the lifeblood of your vehicle. It keeps your transmission and other components functioning properly, but even ATF will wear out. When that happens, there are several symptoms that may occur:

  • Slipping Gears: This symptom takes place when gears get stuck after shifting into gear. The transmission will not stay in gear and also fails to downshift when braking or coming to a stop. This problem usually occurs after fluid has worn out over time; however, it can happen suddenly if there is low ATF in the system or if water gets mixed in with the fluid because both degrade the ATF’s lubricating properties. If this issue continues, you may need a new transmission assembly installed.
  • Gears Grind: Gears making a grating sound while shifting indicates that there is metal to metal contact. This can happen if fluid has been low or contaminated, causing the transmission parts to scrape against each other. Replacing ATF will not solve this issue because it’s the actual gears themselves wearing out. In some cases, you may be able to have your gears polished and reconditioned so as to remove any burrs from contacting the gear faces.
  • Grinding Noise: A grinding noise when going from park into drive or reverse can mean bad input or output speed sensors, which are common issues in automatic transmissions. Replacement of these sensors will resolve the grinding noise but does not fix a faulty ATF, which will likely need replacing after time anyway since it is being affected by all of these issues.
  • Fail to Start: If your vehicle fails to start, it could be because the ATF is too low or contaminated. It can also mean that there is water in the fluid or air bubbles blocking the flow of fluid. Replacing ATF will not fix this issue but flushing out all contaminants and air bubbles may get your engine running again, at least temporarily until you manage to replace the ATF.

Noisy during Driving: The most common noise that may come from your transmission occurs when accelerating or driving uphill. This sound comes from the torque converter because it operates under higher pressure than other parts within the transmission like gears and bands, causing strain on components like bearings which can make wear out quickly. This symptom is easy to diagnose because it’s so common but unfortunately, ATF replacement will not solve the high pressure in torque converter. Replacing ATF before other transmission components have worn out can help your engine last longer.

You may be wondering if you should flush or completely replace your Automatic Transmission Fluid (ATF).

Transmission flush

Transmission flush vs Fluid Change

Transmission flush is a service that includes draining the pan and cleaning the transmission oil cooler screen. The goal of the service is to remove old fluid from inside your car’s transmission system as well as lower pressure points as a way to keep contaminants out.

you should have this service performed at 30,000 miles or one year – whichever comes first – after you purchased your vehicle. Then every five years or 50,000 miles thereafter. If pan gasket leaks are repaired prior to performing flushing, it can be done any time after that depending on condition of engine oil and the performance of the car itself.

In general, try changing your transmission fluid once a year or every 30,000 miles to keep it running as long as possible.

Reasons to flush the ATF

If your vehicle’s transmission fluid has not been changed in a while, or if you have recently started noticing that your car is having trouble shifting gears, then you may want to flush the ATF out of the cooling system. Flushing ATF from a cooling system can be done relatively easily and economically. Benefits of flushing automatic transmission fluid from the cooling system include reduced wear on transmissions and improved driving performance.

Fluid Change

Transmission flush vs Fluid Change

A fluid change is when you replace the engine oil or transmission fluid in a vehicle. Despite what you might think, this is actually a normal and necessary thing to do in order for your car to run properly and last a long time. Over time, fluids like motor oil will break down and lose their effectiveness. This is why it’s important that you flush your transmission fluid out on a regular basis. By removing and replacing these fluids at higher mileage intervals, you avoid draining any extra contaminants into the new oil. Fluid changes are one of the cheapest things you can have done on your car, so it’s important to know how to do it yourself!

When to change the ATF

When to change the ATF, or transmission fluid, is a question that often arises among car owners. This article will offer some insight on when to change your automatic transmission fluid.

The engine’s temperature causes the ATF to become thinner and warmer it also causes exhaust gases to break down the additives in the fluid. The heated air causes oxidation which eats away at the additives and reduces their effectiveness over time. Heat can cause other problems such as vapor lock where bubbles of hot air get trapped in part of the system and prevent cooling liquid from reaching the radiator so overheating occurs. Hot weather also increases gasoline evaporation which can reduce performance, fuel economy and emissions while increasing oil leakage because of reduced lubrication properties.

Transmission flush vs Fluid Change

Transmission flush vs Fluid Change

Both transmission flushes and fluid changes are performed with the goal of replacing old, contaminated fluid with new, clean fluid. However, they differ in technique and how thoroughly they accomplish this task:

  • A transmission flush replaces both old and contaminated fluid with fresh fluid throughout the entire system via a thorough but simple process that is less likely to introduce contaminants than a standard drain-and-fill procedure. Transmission flushes do not completely replace all the internal filter/separator elements nor does it remove all debris from inside the system as these steps require specialized equipment or tools which can introduce additional contamination if done improperly. Fluid exchanges such as those found at quick lubes typically use automated “suck and refill” machines; these sort of services are not recommended as they can introduce contaminants into the system.
  • In a fluid change, only old and contaminated fluid is replaced with new fluid by removing the drain plug to allow for draining followed by refilling via a new factory-fill of fluid. While this method does remove some debris from inside the system, if degreaser or components are used in conjunction then there is a greater chance that any debris left inside will be scrubbed into the internal filter/separator elements if flushed through too quickly. Fluid changes can also be incomplete at times due to component clogging (by debris) which may not be noticed until later on when symptoms start occurring; these symptoms may lead to misdiagnosis and additional work/costs for no reason. In contrast, a transmission flush is complete and thorough from the get-go.

Transmission flush advantages:

  • A transmission flush is the most thorough method to remove old, contaminated fluid and debris that’s inside the system.
  • Old fluid contains contaminants which can damage internal components if not removed; therefore fresh, clean fluid helps keep your transmission running in good condition for longer.
  • Because of this thoroughness, it is also more likely to correct problems related to internal filter/separator element clogging than a simple fluid change. Additionally, unclogged filter/separator elements cannot be guaranteed with any type of service including flushes unless they are performed by specialized equipment (that actually checks each component after servicing) or parts were replaced on every service due to internal failures before symptoms started occurring – which isn’t usually the case.
  • A properly performed flush will have all filter/separator elements restored to their original dimensions by removing any debris that’s left behind after flushing through them. This means if clogged components are not discovered until later on there should be no risk of component failure due to lack of flow or other issues related to clogging. Regular fluid changes cannot provide this level of protection against future failures.

Transmission flush disadvantages:

  • Flushes can be time consuming and costly since using specialized equipment, chemicals, and tools is required in addition to standard service costs. Additionally, services can take too long for certain shops so they may refuse or cut corners which could lead to incomplete work, safety concerns, and possible warranty issues.
  • Using chemicals in conjunction with flushes can lead to safety concerns since most are not designed for use inside the transmission system. Using these types of products have led to lawsuits when injuries or damages occurred due to negligence or misuse of these products. For example, using automatic transmission fluid in a power steering system would cause the power steering pump and lines to fail; this is because ATF cannot withstand high pressures and temperatures of the power steering system which is why it was designed for use solely within an automatic transmission (where pressures and temperatures are much lower) and never the other way around. Other components such as pumps and fittings may also be considered at risk if compatibility issues exist between fluids used during flushing – which isn’t always caught beforehand.
  • Flushes can be incomplete if either not performed by a professional, or if they are done too quickly and components such as the filter/separators clog which results in debris scrubbing into internal elements. This leads to component failure and other expensive damage later on due to lack of proper cleaning before this occurs; using specialized equipment is required because it performs the service at a much slower rate which reduces the chance that any debris remains behind (or gets through) to cause downstream issues.

Transmission flush alternatives:

If you wish to avoid paying for a flush, which can be time consuming and costly, but still want your transmission serviced properly then flushing your cooling system during every fluid change should allow you to reap the same benefits. One of the most effective ways to do this is by filling your transmission fluid through the radiator filler neck or from an external cooler which can easily be done during a regular oil change.

However, it’s essential that you use a compatible transmission fluid for both systems – using automatic transmission fluid in the cooling system or power steering system would damage those components as explained above. This means you must use a Dexcool compatible ATF such as Amsoil MTG Transmission Fluid . Also make sure all air pockets are removed from your cooling system before starting any service to ensure maximum flow and mixing of fluids between systems.

Although not as thorough as flushing, this method can save you time and money since it’s less expensive than paying for a full flush and since other components such as the filter/separators are not removed it greatly reduces the risk of them becoming clogged. Only performing regular fluid changes also means that should any defects occur during flushing there is no risk to further damage to your transmission components due to lack of protection against future failures.

How to change the Transmission Fluid Yourself

Transmission flush vs Fluid Change

When trans fluid is low, it can damage the transmission and cause problems with power. This article will show you how to properly flush the old fluid out of your truck’s cooling system stack overflow tank, and replace it with new fluid in order to ensure a reliable vehicle for years to come.

Step 1: Prepare Area and Vehicle

You will need:

  • Hydraulic jack and jack stand (follow your vehicle owner’s manual for specific set up)
  • Monitors with appropriate adapters to check trans fluid level in the automatic transmission
  • An assistant – one person is needed to remove old fluid from the cooling system stack overflow tank, while another is needed to add new fluid after it is flushed
  • A catch pan large enough to hold all of the removed fluid from the cooling system stack overflow tank

Step 2: Raise Vehicle High enough to work under it with a hydraulic jack

Use a hydraulic floor jack and a pair of sturdy jack stands. Follow manufacturer’s safety recommendations when working under a lifted vehicle. Never get underneath a vehicle that has only been lifted with a scissor jack.

Step 3: Locate cooling system stack overflow tank and remove lid, dipstick and magnetic plug

The cooling system stack overflow tank is located in the engine bay near the back of your vehicle, on the passenger side. It has a lid with three lines for fluid levels marked on it. Unlatch the lid and set it aside. Inside you will see a stick with a pink plastic handle, called a dip stick (A). To the left of this stick is another stick (B) with a small black magnet attached to its end – this is used to pull any ferrous particles out of the transmission pan. Remove this second stick by pulling it straight up out of its holder (C).

Step 4: Check and/or replace magnetic plug and dipstick

At this point, your assistant should check the transmission fluid level with a properly calibrated tool. If the oil is low, it may be necessary to add new fluid. Be sure to follow proper safety precautions when handling and adding transmission fluid – it is flammable.

As an alternative to removing the magnetic plug in Step 3, you can dump old fluid from the cooling system stack overflow tank into a catch pan while removing only the lid of the overflow tank with three lines on it. This method will not require that you drain any additional fluids or remove any more components. Just make sure your assistant keeps checking your transmission fluid levels before re-filling in order to ensure the fluid is at an acceptable level.

Step 5: Use catch pan to drain all of old transmission fluid from cooling system stack overflow tank into a large bowl or bucket

Next, lower your vehicle back down onto its tires. With your assistant’s help, use a catch pan under the coolant stack overflow tank and remove the lid with three lines on it (the one you just removed in Step 3). Pour all of the contents of this reservoir into a large bowl or bucket – be careful not to spill any fluids! Make sure that you’ve drained all of it.

Step 6: Fill cooling system stack overflow tank with new transmission fluid and replace lid with three lines on it

Once your old trans fluid has been replaced with new fluid, pour the old fluid into a large bowl or bucket. Then slowly add new transmission fluid to your cooling system stack overflow tank until it reaches the “Full” line (D). Be sure not to overfill.

Step 7: Refill Transmission Fluid After Filling Cooling System Stack Overflow Tank

After you have replaced 1/4 of the transmission fluid in the cooling system stack overflow tank with new fluid, change out assistant and have them refill your transmission. You will need a 1/2-inch socket wrench and 2 quarts of fresh automatic transmission fluid for this part of the job. One person should be under the car refilling while another checks for leaks around underneath – if you see any oil leaking from the area under the engine, you should probably let your mechanic know.

Step 8: Dispose of old transmission fluid

After the draining, flushing and refilling are completed, it is time to dispose of all of this used fluid. Drain your catch pan into an approved container, then properly discard any remaining waste oil at a local recycling center or automotive shop that accepts oil. Never pour used transmission fluid down the drain – it will solidify in pipes and cause serious damage. Your help with this part is great appreciated! Be sure they understand not to dump their old fluids down storm drains or streams as these can contaminate water supplies.

The following are possible reasons for being unable to flush out the transmission system rather than replacing it altogether:

  • The transmission pan is inconsistent. There may be some debris or dirt stuck on it which causes the whole process of draining to fail.
  • The fluid lines are clogged with metal particles, preventing all of the old trans fluid from being flushed out.
  • There is a crack in the line which causes the new fluid to leak into another part of the car before reaching your trans system.
  • Your car has an automatic transmission that constantly recycles its own fluids rather than sending them back into the engine as yours does, so this recycling feature might prevent you from being able to flush out your transmission completely.
  • Many people cut corners by using water instead of all new fluid during the flushing process since there are not many components, but this can contaminate your cooling system and must be avoided at all costs.

If the old transmission fluid has been allowed to deteriorate, you may need a new trans system regardless of how many times you try to flush it out. Depending on the severity of the damage done, this can range from a few hundred bucks for a used trans system with 80k miles of life left in it up to thousands of dollars for a completely rebuilt one without a warranty or guarantee of quality. If you find yourself in this situation, I recommend going ahead and getting a replacement rather than trying over and over again just for the sake of being able to say that you did everything possible – there are no points awarded for effort!

Step 9: Put drain pan back in place and replace oil pan drain bolt

Once the transmission fluid is flushed out, it’s time to put everything back where you found it. Replace the old fluid in your catch pan with fresh new oil under your car on a level surface. Be very careful not to spill any on yourself or the ground. It may seem like an easy task but this liquid can wreak havoc on fabrics and soil. While you’re underneath there, go ahead and make sure that all of your tools are accounted for and safely stored away up above.

Once you have successfully completed this job, congratulations! You will never need to worry about buying automatic transmission fluid again because you will now know how to flush out trans systems effectively. If you’ve experienced symptoms of problems with your transmission system, you may want to consider coming into our shop for a check-up. We are experts at diagnosing and repairing these systems so that they can continue to serve you well!

If the whole process seems too daunting for you, contact your mechanic.


As stated earlier, flush out your cooling system if you notice the transmission fluid is leaking into your radiator. If you are unable to stop the leak or are uncertain if it’s happening, this process will fix that problem. While changing the ATF is important in regular basis. Be sure to follow every step of the instructions carefully for good results. Once completed, check for leaks again and enjoy a fresh new cooling system!

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