How To Perform A Transmission Flush On Your Vehicle - SlashGear (2024)

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How To Perform A Transmission Flush On Your Vehicle

Cars

How To Perform A Transmission Flush On Your Vehicle - SlashGear (4)

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Your car's transmission is a vital part of its anatomy. It's responsible for taking the raw power created by the engine and scaling it down to various driving situations. The transmission is what makes it possible to drive at different speeds, take off from a stop, and decelerate when it's time to slow down. But the transmission isn't just a magic box that does all of that on its own. Transmissions work using a particular type of hydraulic fluid. This pressurized fluid helps actuate valves inside the transmission, move gears, and lubricate all moving parts. While transmission fluid is durable and long-lasting, it's subject to degradation over time and will eventually lose its ability to help your transmission function properly.

Because transmission fluid breaks down over time, it must be replaced periodically. Most manufacturers provide specific schedules for transmission fluid flushes and replacements. A transmission flush is a relatively simple procedure, but the steps can vary depending on your car's make and model. There's also a distinction between a transmission flush and a transmission fluid change.

Generally, a flush involves draining the transmission fluid, connecting a machine or other apparatus to the transmission cooler lines to purge any remaining old fluid, and then refilling the system with fresh fluid. However, some vehicles require additional steps, like replacing the transmission fluid filter and installing a new pan gasket. A transmission fluid change, on the other hand, is a simple drain and fill procedure. Typically, a drain and fill is all you'll need to do, as flushes are more time-consuming and require more equipment. That said, there are ways to perform a flush at home if you're a confident DIYer. Let's dive in and take a deeper look at transmission flushes and how to perform them.

How to flush an automatic transmission

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Flushing your transmission is a fairly straightforward task. However, the procedure can differ slightly from car to car and depending on your transmission type. For automatic transmissions, including continuously variable transmissions (CVTs), the steps are relatively similar.

  1. Lift the vehicle off the ground.

  2. Remove the transmission fluid drain plug or remove the pan and allow the old fluid to drain (you'll have to remove the pan no matter what if you plan to replace the filter).

  3. Remove the old filter and replace it while the pan is off.

  4. Clean the old gasket material and the drain pan mating surface before installing a new gasket.

  5. Torque the pan bolts to their proper specification.

  6. Replace the drain plug if applicable.

  7. Lower the car and remove the transmission fluid dipstick.

  8. Measure the amount of fluid that you drained from the transmission, and add that same amount of clean fluid to the transmission via the dipstick tube.

  9. Locate your car's transmission cooler lines.

  10. Attach one end of a hose to the outlet or return line and place the other end in a bucket or drain pan.

  11. Start the engine.

  12. Allow the new fluid to drain into your bucket (this is the flushing procedure that will clear out any grime and gunk from the transmission).

  13. Continue adding more fluid to the transmission until the liquid leaving the return hose looks bright red and clean.

  14. Turn off the engine and reconnect the return line.

  15. Start the engine and check your transmission fluid level using the dipstick.

  16. Add more fluid until the level is within the appropriate range.

  17. Test drive your car.

How to flush a sealed transmission

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A sealed transmission does not have a dipstick, meaning you can't check the fluid level or fill the transmission with new fluid from the engine bay. Instead, these transmissions typically have a drain hole and a fill hole located directly on the transmission. Flushing a sealed transmission is significantly more complex than flushing an unsealed one. You'll need a pump, which you can find at most auto parts stores, a piece of hose, and a clear container.

  1. Check your vehicle repair manual to determine your car's overall transmission fluid capacity.

  2. Remove the transmission drain plug and allow the fluid to drain into a clear container.

  3. When the fluid stops draining, replace the drain plug.

  4. Measure the amount of fluid that drained out of the pan.

  5. Locate the fill plug and use your pump to add the same amount of fresh fluid that you previously drained.

  6. Locate the transmission cooler hoses and disconnect the return line.

  7. Attach a piece of hose to the return line and place the other end in your clear container.

  8. Start the engine and drain one quart into the container.

  9. Stop the engine and use your pump to add one quart to the transmission.

  10. Repeat this procedure until you've drained and added the maximum fluid capacity for your car (at that point, the fluid leaving the return hose should be red and clean).

  11. Replace the fill plug.

  12. Take your vehicle for a test drive.

How to flush a manual transmission

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Manual transmissions differ from automatic transmissions in that they're much simpler and easier to maintain. These transmissions do not have filters or cooler lines, meaning you can't flush them in the same sense that you can flush an automatic transmission. Instead, when it comes to servicing a manual transmission, you'll basically just be performing a drain and fill. Manual transmissions can be sealed or unsealed, meaning you may need a pump to complete the procedure. You can determine whether your car has a sealed transmission by checking the engine bay for a transmission fluid dipstick. Follow the procedure below to replace the fluid in your manual transmission.

  1. Lift the car off the ground.

  2. Remove the transmission drain plug or the pan and allow the fluid to drain.

  3. Replace the plug or pan (if you removed the pan, you'll need to replace the gasket and retorque the bolts to their proper specification).

  4. If your transmission is sealed, measure the fluid that you drained and pump the same amount of clean fluid in through the fill hole.

  5. If your transmission is unsealed, lower the car and fill the transmission with the appropriate amount of fluid.

  6. Start the engine and let it run while you continue to check the fluid level.

  7. Add more fluid if necessary.

  8. Take your car for a test drive.

When do you need to perform a transmission flush?

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Your car's manufacturer provides a maintenance schedule for routine services, including transmission fluid flushes. The intervals will depend on various factors, including your vehicle's make and model, the type of transmission it uses, and the type of fluid. You can find this information in your owner's manual, your repair manual, or by contacting your local dealership. However, most cars need a transmission fluid service every 30,000 to 100,000 miles.

Outside of regular transmission service, you may need to replace your fluid if you experience any symptoms of transmission damage. Some of the most common signs that your transmission fluid is bad include an overheating transmission, dashboard warning lights, jerky or irregular shifting, and stalling issues. Over time, transmission fluid can accumulate debris and metal shavings. It's vital that you replace the fluid regularly to avoid damage and keep your transmission shifting smoothly. The best way to protect your transmission is to follow your manufacturer's instructions and keep up with a routine maintenance schedule.

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How To Perform A Transmission Flush On Your Vehicle - SlashGear (2024)

FAQs

How to perform a transmission flush? ›

Disconnect the transmission cooler line that enters the radiator with hot fluid. With a thin funnel in the dipstick tube, start the engine and begin pouring the clean fluid into the funnel. As it's going in, old fluid is being pumped out of the cooler line into your drain pan, flushing contaminants from the system.

Why not to do a transmission flush? ›

A theory here is that flushing can dislodge debris that's trapped in some of the internal passages, allowing it to clog up other passages downstream. It could also blow out old seals that are otherwise doing their job.

How much should a transmission flush cost? ›

Drivers can expect to pay $125 to $250 for a transmission fluid flush service. This is approximately twice as much as a transmission fluid change. This is due in large part to the additional fluid required. A flush will take 12 to 22 quarts, while a fluid change requires 5 to 7 quarts.

Can you flush water out of an automatic transmission? ›

Usually, some amount of water will come out of suspension and form white gummy masses in various areas of the unit. This is why the unit cannot be flushed to remove all of the water. In addition, the presence of water will start rust forming on the ferrous metal parts throughout the unit.

What is better, transmission flush or drain? ›

Which is Better? In many cases, the transmission flush is a bit more effective. However, it can also be more expensive.

What do you use to flush transmission lines? ›

LUBEGARD Kooler Kleen Trans Flush uses a proprietary mix of detergents to safely clean transmission lines in automatic, CVT, DCT and manual transmissions. This product works without any water to remove grease, dirt, grime, and metal shavings that can clog up the lines.

Can a transmission flush ruin your car? ›

Despite some potential advantages, a transmission flush also carries certain hazards which, if not properly managed, can potentially worsen existing transmission problems or create new ones. Power flushing, for instance, utilises force to expel old fluid and contaminants.

Are transmission flushes a waste of money? ›

Performed properly, a transmission flush will not damage a transmission. Are transmission flushes a waste of money? No! Transmission fluid flushes remove contaminants that could hurt your transmission, much the same way that engine oil is changed to clean the engine.

Does your car run better after a transmission flush? ›

After a transmission fluid flush, you may notice that your vehicle shifts smoother, and that your transmission operates better than before.

How long does it take to flush a transmission? ›

A trained mechanic can perform a simple transmission flush in three to four hours using a commercial flushing machine or pump inlet. A transmission fluid change takes just about 30 minutes.

What mileage is good for a transmission flush? ›

What is the recommended service interval for transmission flushes? Each manufacturer recommends the transmission flush interval for their vehicles; however, most recommend that the transmission is flushed every 30,000 to 50,000 miles.

How many years does transmission fluid last? ›

Automatic: Every 60,000 to 100,000 miles

If you drive manual, most manufacturers will recommend changing your transmission fluid every 30,000 to 60,000 miles. If you have automatic, you can typically boost that range up to 60,000 to 100,000 miles. There's no harm in changing your fluid early.

Can I do a transmission flush myself? ›

» A transmission flush can be performed (DIY) using the transmission's pump without a flush machine. A transmission flush is a process in which the fluid in an automatic transmission is flushed out of the transmission and replaced with new ATF.

What is the easiest way to drain transmission fluid? ›

Place a large catch pan under the transmission, decide which end or corner of the pan that you want the fluid to drain from and start losing the bolts at that point, working your way towards the opposite end of the transmission pan. After the pan is dropped on one end, allow the fluid to drain as much as it will.

How to tell if water is in transmission? ›

All you'll need is a hotplate and a clean pan. Just pour a small sample of the transmission fluid into the pan and put it on the hotplate to heat up. Transmission fluid will burn and smoke, but if the fluid's contaminated with water or coolant, it'll start to boil and spit.

Can I flush my transmission myself? ›

A transmission repair shop or dealership service center will use a special machine to flush a transmission, but you can do it yourself using the transmission to flush itself.

How many hours does it take to flush a transmission? ›

How long does it take to flush a transmission? A trained mechanic can perform a simple transmission flush in three to four hours using a commercial flushing machine or pump inlet. A transmission fluid change takes just about 30 minutes.

Do you leave the car running when adding transmission fluid? ›

Your car's engine should be running when you add fluid to the transmission, but you should have the transmission in park and the handbrake activated for safety. Check the owner's manual for instructions on selecting the correct transmission fluid for your vehicle.

How to get air out of transmission fluid? ›

Loosen the bleeder valve and pull a vacuum with the pump. You will need to use the catch can that comes with most vacuum pumps to catch the fluid. When all the air bubbles are gone then the system is bled. This may take a while so keep check of the amount of fluid in the reservoir and do not let it run out.

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