How to Change Transmission Fluid for DIY Auto Maintenance

Learning how to change transmission fluid and filters is relatively simple, especially if you are familiar with the process of changing the oil in a vehicle. However, transmission fluid replacement is a maintenance task that is often overlooked, so it’s necessary for many automotive DIYers to learn how to replace transmission fluid.

If you don’t change transmission fluid at recommended intervals, the fluid becomes dirty, which greatly reduces its effectiveness as a lubricant. This results in increased friction, heat, and wear and tear on the transmission.

Signs that it’s time to replace transmission fluid in your vehicle include spikes in RPM before shifting, grinding sounds, sudden jarring up and downshifts, and burning smells that indicate there is an increase in the friction among the moving parts of the transmission. To help avoid lasting problems with your transmission, learn how to change transmission fluid and make changing transmission fluid a regular part of your automotive maintenance schedule.

BEFORE YOU BEGIN

Transmission fluid only needs to be changed about once every 30,000 to 60,000 miles for manual transmissions and every 60,000 to 100,000 miles for automatic transmissions. Be sure to check the owner’s manual for the manufacturer’s recommended maintenance schedule to get an estimate of the appropriate transmission fluid replacement interval for your specific vehicle.

You can also open up the hood of the vehicle and look for the red-handled transmission fluid dipstick to check the transmission fluid level in a car. If the transmission fluid looks clean, but the levels are low, then you may just need to add fluid to the system, but if it looks discolored, then it’s a good idea to change the fluid.

STEP 1: Park and elevate the vehicle.

Like many maintenance tasks on a vehicle, a transmission fluid change begins with parking the vehicle in a safe space, like a garage or level driveway. Put the vehicle in park, take out the keys, and apply the parking brake.

To get access to the transmission fluid pan for the purpose of draining the old transmission fluid, you will need to use a jack to elevate the vehicle off of the ground. With the vehicle suspended on the jack, you can position wheel chocks behind the rear tires to prevent the vehicle from moving or shifting while you work.

An alternative to using a jack to lift up the car is to drive the vehicle up onto steel wheel ramps. These tools are made to support the weight of a vehicle and they have depressions at the top of each ramp to help prevent the vehicle from shifting or otherwise moving. Just make sure to allow the engine about 5 to 10 minutes to cool down after turning it off, so that you aren’t working with incredibly hot parts and transmission fluid.

STEP 2: Locate the transmission fluid pan.

Similar to changing the oil, you will need to slide under the vehicle and locate the transmission fluid pan. Typically, this pan can be found on the left or right of the engine bay on front-wheel or 4-wheel drive vehicles, while it is located under the center console area on rear-wheel-drive vehicles. The pan has a broad, flat shape and it’s attached to the bottom of the transmission with six to eight bolts, so it should be relatively easy to find.

Check whether the transmission fluid pan has a drain plug for releasing the transmission fluid or if you will need to remove the entire pan to drain the transmission fluid. If your transmission fluid pan doesn’t have a drain plug, make sure that you find a drain pan that is at least as wide as the transmission fluid pan to avoid creating a mess under the vehicle.

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STEP 3: Drain the old transmission fluid.

Put on gloves to keep your hands safe during the replacement process and wear safety glasses to protect your eyes from falling transmission fluid. If the transmission fluid pan has a drain plug, then use a socket wrench or crescent wrench to loosen the plug and begin to drain the old transmission fluid into a suitable transmission drain pan.

Transmission fluid pans without a drain plug will need to be completely removed. Use a socket wrench or crescent wrench to loosen and remove the bolts at one end of the transmission fluid pan and position the drain pan to catch any falling transmission fluid. Proceed to loosen and remove the bolts along both sides of the fluid pan, allowing the transmission fluid to continue to drain. Completely drain the remaining transmission fluid by removing the final bolts and freeing the pan.

Put the transmission fluid pan and the bolts in a safe spot until reinstallation. Check the contents of the drain pan to see if there are any large or odd-shaped chunks of metal that could indicate severe damage. It’s normal to see metal shavings in the old transmission fluid, but larger pieces are a sign that the transmission is in need of immediate attention from an automotive professional.

STEP 4: Inspect the transmission fluid filter and change if necessary.

After draining the transmission fluid from the vehicle, remove the transmission fluid pan entirely to access the transmission fluid filter. Inspect the filter for any damage, like cracks or leaks. In most cases, the filter doesn’t need to be replaced every time the transmission fluid is changed, but inspecting it is a good way to identify problems before they can have a greater impact on your transmission system.

If the transmission fluid filter requires replacement, purchase a compatible filter for your vehicle, then slide under the car and remove the bolt that is securing the old filter. With the bolt removed, pull down to take the filter off. Take this opportunity to tighten the transmission valve body bolts, but make sure not to over-tighten them.

Lubricate the new filter O-rings with transmission fluid and line up the fittings with the transmission valve body. Push the filter fittings in to properly seat the O-rings, then use the bolt that you had previously removed to secure the new filter to the vehicle.

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STEP 5: Secure the transmission fluid pan.

With the new filter in place, you are ready to reinstall the transmission fluid pan. Line up the pan according to the bolt pattern, then hand-tighten the bolts to hold the pan in place. Use a socket wrench or crescent wrench to tighten the bolts, but avoid over-tightening to prevent accidentally cracking, warping, or otherwise damaging the pan. If your transmission fluid pan has a drain plug, be sure to reinstall the plug before sliding out from under the vehicle.

STEP 6: Refill the transmission fluid.

Figuring out how to fill transmission fluid is straightforward. Lower the jack or back off the wheel ramps so that the vehicle is sitting on the ground again, then open the hood of the vehicle. Locate the transmission fluid port, which is typically distinguished by the red dipstick. You can pour the transmission fluid directly into the port, but it’s advised to use a funnel to prevent spilling the fluid onto nearby engine components.

There are different kinds of transmission fluid, so check your owner’s manual to figure out the correct type of transmission fluid. After refilling the fluid, turn the vehicle on and allow it to run for a few minutes. Pull the transmission fluid dipstick out to verify that the fluid is at the correct level, then close the hood of the vehicle. If the transmission fluid level is still low, then add more fluid to top it up to the correct level before closing the hood.

STEP 7: Check for leaks.

Unless you plan on refilling the transmission fluid every time you want to drive the car, it’s important to check for leaks before driving the vehicle. Place a large piece of cardboard under the transmission fluid pan and allow the vehicle to run for several minutes. If the cardboard shows signs of dripping transmission fluid, then you will need to slide back under the car to try and resolve the problem.

Possible solutions for leaks include simply tightening the bolts, replacing the transmission fluid pan gasket, or even replacing the entire transmission fluid pan if the leak seems to be caused by damage to the pan.

Final Thoughts

Transmission fluid is a harmful substance that can do lasting damage to the environment if it’s simply poured down the drain. It can affect the local vegetation, wildlife, and water sources like rivers, ponds, and lakes. To avoid causing harm to the environment and the community, dispose of the old transmission fluid properly.

Most auto parts stores and body shops have fluid recycling programs that allow you to simply drop off motor oil, transmission fluid, and other hazardous fluids from the vehicle. Just keep in mind that there will likely be a small disposal fee to cover the cost. If your local auto parts store does not have a fluid recycling program then you may need to take it to your local government recycling facility for proper disposal.