Does My Car Need Transmission Flush Service?

A quick flush of the transmission fluid usually takes less than one hour. This is because it only needs pumping fresh transmission fluid through the transmission cooling lines. Extra service like changing the filter, adjusting the bands, cleaning the pan, or checking the valve body can take 3 to 4 hours. Before a flush, you should check the color of the transmission fluid. If it’s too dark, clumpy, or dirty, you should skip the transmission flush. Just change the transmission fluid and filter instead.

In this guide, I’ll explain how long does a transmission flush take. As a car enthusiast like me, you will be well aware of transmission oil change requirements.

The recommended service interval for vehicle transmission fluid flush is typically 60,000 miles or every 3 to 4 years, depending on your vehicle model.

However, transmission fluid can be changed any time it starts to look dirty, or as soon as your transmission starts shifting hard.

If you want to get a quick answer, you can chat with a virtual mechanic for free.

In the last section, I’ve included comments from forums where users share firsthand experiences of transmission fluid flushing. Be sure to check out that section for real insights.

Some Key Insights for You
  • Transmission flush involves pumping new fluid to replace old fluid. Takes 1 hour or less.
  • Should inspect fluid first – if too dark/clumpy, just change fluid and filter, don’t flush.
  • Fluid wears from heat and metal shavings from gears. Needs change every 60k miles.
  • Flush pushes fluid back and forth to completely replace. Change only drains pan.
  • Only flush if fluid is still red/brown. If black, just change transmission fluid.

Why Transmission Fluid Wears Out?

The transmission fluid gets worn out from the heat it faces during some driving.

The transmission is complex. But really it has two main parts – a torque converter and a drive train. The transmission fluid lubes the parts in the transmission. It also keeps them cool.

The fluid in automatic transmissions breaks down over time from the heat, just like other lubes. Also, the gears in the drive train make tiny metal pieces. These can damage the transmission.

Over time, the transmission fluid loses its slipperiness. So it can’t lube the clutch pack well. The transmission fluid heats up fast. This wears the clutch pads.

The metal pieces and pad material mix with the transmission fluid. They reduce its quality over time. So the transmission needs a flush.

What Is A Transmission Flush?

Transmission flush simply means pumping the fresh transmission fluid under pressure through transmission cooler lines to replace the dirty transmission fluid inside the transmission system (torque converter, transmission pan, valve body, and clutch packs) with fresh transmission fluid.

The procedure involves removing the transmission pan, torque converter, and valve body. Flushing the transmission fluid will remove any debris which may have entered the transmission system.

Transmission flushes are usually recommended every two years, or as recommended by your vehicle manufacturer. They are also a good way to make sure that your transmission is working correctly.

A transmission flush costs roughly $100 to $250, depending on the vehicle.

What Happens During A Transmission Flush?

A transmission flush replaces all the old and dirty transmission fluid. The old transmission fluid has metal pieces and other stuff floating in it.

When you do a flush, all the old transmission fluid comes out. Then the transmission gets filled up with nice clean fluid.

Doing a transmission flush helps because:

  • The clean transmission fluid won’t hurt the transmission parts
  • Old fluid can damage the insides of the transmission

A good flush includes:

  • Checking the fluid and filter(s)
  • Looking for any leaks
  • Inspecting the transmission pan for rust or damage

What Is The Difference Between Transmission Flush and Transmission Oil Change Service?

The main difference between a transmission flush and a transmission oil change is that a transmission flush involves pushing the fresh transmission fluid through the transmission back and forth while a transmission fluid change only involves draining the transmission fluid from the transmission pan by simply opening the drain plug, and replacing the transmission filter.

Transmission oil change and servicing only removes 1/3rd of transmission oil as the remaining transmission oil is still present in the torque converter and transmission cooler. In transmission flush, service companies do not drop the oil pan. They just run fresh transmission fluid through the transmission cooler lines of the transmission and replace it with 100% of the old transmission fluid.

Whether your vehicle needs transmission flush or transmission change service, you can find it in your owner’s manual. It is mandatory to change transmission fluid every 60,000 miles or every 3 to 4 years. But the requirement of transmission flush is dependent on your vehicle’s model.

Signs You Need A Transmission Flush

  • The transmission fluid color is blackish brown or yellow after wiping the transmission dipstick with a white piece of cloth.
  • Transmission shifts hard, especially when it is cold which results in the car shaking at idle.
  • Transmission is jerky due to the clutch slipping.
  • Groaning noise is coming from the transmission.

Is Transmission Flush Good Or Bad?

Transmission flush can only be bad and cause damage to the transmission if the color of the transmission fluid has become dark black due to not changing of transmission fluid at recommended intervals. 

color of dirty transmission fluid
color of dirty transmission fluid

If your vehicle has high mileage, and transmission fluid has not been changed for a long time, it will have metal shavings and small chips of clutch pad material suspended in it. The suspended chips of a clutch pad material will helo clutches engage and maintain the grip.

If you perform a transmission flush at this stage, two damages will occur to the transmission:

  • The clutch will slip because the fresh transmission fluid will not have any material suspended in it to engage the clutch.
  • The metal shavings hanging out in the transmission pan and microscopic debris in the transmission will be forced back into the valve body, solenoids, and clutch packs, thus blocking the oil from properly applying pressure to the band.

Due to the above two reasons, transmission flush has established a big myth among car owners that it will damage the transmission. If you never let the transmission fluid become too dirty and dark, transmission flush won’t harm your vehicle’s transmission system.

Moreover, some transmission service companies use high-pressure flush machines to pump fresh transmission fluid through the transmission and replace it with the old one.

These high-pressure transmission flush machines may not meet the manufacturer’s specifications and can damage the delicate internal passages and seals of the transmission valve body. This type of transmission flush is called a power flush, which I won’t recommend to you for your vehicle.

Best DIY Method To Perform Transmission Flush

To save a big chunk of your money, instead of using a transmission flushing machine that makes high pressure in the lines to flush out the old transmission fluid, I recommend you do a regular flush using your transmission’s gear pump power.

You should take these steps for a transmission flush:

  1. First, check the transmission fluid health. If it’s reddish brown or yellow, it’s fine to flush. If it’s dark black with particles, just change the fluid and filter. Use a white cloth to see the color.
  2. Remove the transmission pan and clean it well. Transmission pans have magnets to catch metal pieces. Clean with brake cleaner.
  3. Also clean the transmission filter.
  4. Fix the transmission filter and tighten the transmission pan.
  5. Find the transmission cooler inlet and outlet lines. The location depends on your vehicle. The manual can help find them. The lines are near the radiator.
  6. It may be hard to tell which is inlet and outlet. Attach rubber hoses to the cooler lines. Put the other ends in a bucket and start the engine. The one spitting transmission fluid goes from transmission to cooler. This video helped me.
  7. Confirm the line to the cooler, disconnect it, and connect a hose.
  8. Put the hose end in a bucket to collect old fluid.
  9. Under the hood, remove the dipstick.
  10. Put a long funnel in the dipstick opening.
  11. Use the transmission fluid your manufacturer recommends, with the right capacity. For a Ford 150 it’s 14 quarts.
  12. Start the engine and slowly add fresh transmission fluid through the funnel.
  13. Watch old fluid flow out into the bucket.
  14. Keep adding new fluid until the color changes from yellow or brown to clean red.

Some First Hand Experiences Shared By Users In Different Communities

Our team conducted research across various online communities, forums, and subreddits to gather user comments and opinions on “how long it takes to flush transmission fluid”.

User 1 says:

Have a 2014 Wrangler. Experienced gear slipping and a burning smell. Checked Jeep forums, seemed like a transmission fluid issue. I flushed and replaced the fluid myself in about 1.5 hours. No more slipping or burning smell.

User 2 says:

Own a 2010 Corolla. Started experiencing rough shifts. Checked online forums and figured it might be the transmission fluid. Local garage did a flush and refill in about 35 minutes. Made a huge difference.

User 3 says:

Got a 2018 Challenger. Was experiencing a lag in downshifting. Checked some car forums, and they pointed towards the transmission fluid. Took it to a Dodge dealer, and they did a flush in just under an hour. Shifts perfectly now.

User 4 says:

I’ve got a ’13 Silverado. Felt some slipping in transmission. Read up on it and learned it could be the fluid. Decided to do it myself. It took me about 2 hours, mostly because I was being extra careful. Solved the slipping issue.

Frequently Asked Questions About Transmission Flush

Why Does My Transmission Slip After Fluid Change?

Transmission slips after transmission fluid flush because the old clumped oil is forced back into the valve body, blocking the oil from properly applying pressure to the bands.

Should I Change My Transmission Fluid If It’s Never Been Changed?

You should change transmission fluid if it has never been changed but you can’t perform a transmission flush. If the color of the transmission is dark black and it has suspended particles, you should not perform a transmission flush. However, you should replace the transmission filter and change the transmission fluid by opening a drain plug of the transmission pan.

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