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How To Flush Transmission Fluid

how to flush transmission fluid

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Flushing Transmission Fluid Is an Intermediate Job for Most DIYers. Here’s Everything You Need To Know To Flush Your Transmission Fluid at Home.

What Is a Transmission Fluid Flush?

Automatic transmission fluid is just one of the many fluids that your car depends on to run safe, smooth, and reliable. Like all other fluids, automatic transmission fluid wears out over time and gets filled with contaminants, and then it must be changed to prevent internal transmission damage. A transmission fluid flush is a process that removes all of the old automatic transmission fluid from the transmission and replaces it with new, clean fluid. A transmission fluid change replaces most of the fluid, but some of the old fluid still remains in the system’s supply lines and coolers.

Since the transmission fluid collects particles and grime over time that will interfere with the proper operation of the transmission, flushing it and cleaning the fluid can help improve performance.

Is It Safe To Drive Without Flushing Transmission Fluid?

The transmission fluid works to cool and lubricate the transmission. If it gets dirty, the particles in the fluid can stop it from keeping the transmission cool. As a result, the transmission will create more friction and heat and eventually interfere with how your vehicle shifts and accelerates.

A transmission fluid flush will maximize the transmission’s performance and keep it working and performing for longer. The transmission is one of the most expensive components in a vehicle if it needs replacing, so flushing the fluid is an important service that should be done when you determine that it’s needed.

You can safely drive without flushing the transmission fluid as long as the transmission is working correctly. If you notice any signs of a failing transmission, you should bring your vehicle to a mechanic to have it looked at as soon as possible.

A trained mechanic can flush transmission fluid in a couple of hours. A commercial flushing machine makes the job easier than if you do it at home. If you do it on your own, it can take several hours, and you need to have a place where you can jack up the front of the car. If you bring your vehicle to a mechanic for a transmission flush, it may cost around $400, though it depends on where you go, the type of vehicle you have, and its type of transmission.

If you have a good working knowledge of vehicles and a place where you can do the job, flushing the transmission fluid at home can save you money. It tends to be a dirty job and requires getting under the car, so if you don’t have jacks and jack stands, you will be better off bringing it to a mechanic.

When To Flush Transmission Fluid

You may need to flush the transmission fluid every few years or after you’ve driven somewhere between 30,000 and 100,000 miles, depending on your vehicle and the type of transmission you have. It’s important to check your manufacturer’s recommendation.

What Are Common Symptoms Indicating You Need To Flush the Transmission Fluid?

Here are some signs to look for that will indicate that your transmission needs a fluid flush:

  • Transmission slips
  • Shifting sounds different
  • Shifting feels different
  • Dark red fluid on the transmission dipstick
  • A whining noise
  • Grinding noise

Keep in Mind

It’s important to note that there’s a difference between flushing the transmission fluid and changing the transmission fluid. A transmission fluid change is a simple job where you just drain the fluid and then refill it with new, clean fluid. This process only replaces about 50% of the fluid, but it’s often enough to keep the transmission working correctly. When you flush the transmission fluid, it gets almost all of the old fluid out of the transmission.

Before flushing the transmission fluid, pull out the dipstick and look at the fluid. If you see that it’s dark or has a burnt odor, you should not do the flush. Instead, a transmission fluid and filter change is the recommended service.

Remember to always follow the manufacturer’s recommended maintenance schedule and do this service as advised for your make and model.

During a transmission fluid flush, you can also check the pan and inspect the old fluid to look for issues. It’s important to drop the pan because getting a good look at the fluid and what is in it can give you an indication of what shape the transmission is in.

How To Flush Transmission Fluid

You can take these steps to flush the transmission fluid in your car:

Step 1: Start the Engine and Let the Car Warm Up

Run the vehicle until it reaches normal operating temperature, then turn it off. Place a block behind one of the rear tires, and then use a jack to raise the front of the vehicle.

Step 2: Find the Transmission Oil Cooler Lines

The oil cooler lines run from the transmission to the radiator, carrying the fluid. There are two lines: one brings it to the transmission, and the other brings it from the transmission to the radiator. Disconnect the line that enters the radiator. Place a drain pan to catch the fluid coming from the line.

Step 3: Flush the Transmission Fluid

Take the dipstick out of the transmission and insert the funnel into the fill tube. Get the recommended amount of transmission oil ready and put it close to the funnel. Start the engine and pour all the fluid into the transmission using the funnel. Make sure the engine doesn’t run dry between fluid quarts. Once all fluid has gone through, shut the engine off.

Step 4: Reconnect Transmission Oil Cooler Lines

Now you can reconnect the lines, remove the funnel, and reinsert the dipstick. Make sure you push the dipstick all the way into the tube.

Step 5: Start the Engine

Start the engine back up while the front end of the vehicle is still up on jacks. Check for leaks. If you don’t see any leaks, shut off the engine and lower the vehicle back down.

Step 6: Check the Fluid Level

Once you have the vehicle back down on level ground, turn the engine back on, and at idle, pull out the dipstick to check the fluid level. Wipe the dipstick clean and check it again to confirm.

Still Need Help?

Want an expert mechanic on speed dial who can walk you through DIY repairs and answer any questions? Join FIXD Mechanic Hotline for unlimited access to our Master Mechanics Monday through Friday, 8 a.m. to 8 p.m.

Disclaimer: The guidelines in this article are general and not meant to replace instructions for your specific vehicle. Please consult your owner’s manual, repair guide, or a professional before attempting repairs.

FIXD Research Team

At FIXD, our mission is to make car ownership as simple, easy, and affordable as possible. Our research team utilizes the latest automotive data and insights to create tools and resources that help drivers get peace of mind and save money over the life of their car.

We’re here to help you simplify car care and save, so this post may contain affiliate links to help you do just that. If you click on a link and take action, we may earn a commission. However, the analysis and opinions expressed are our own.

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About the Author

FIXD Research Team

FIXD Research Team

At FIXD, our mission is to make car ownership as simple, easy, and affordable as possible. Our research team utilizes the latest automotive data and insights to create tools and resources that help drivers get peace of mind and save money over the life of their car.

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