How and When to Check Your Transmission Fluid
  • Buying Guides

How and When to Check Your Transmission Fluid

By Michael O'Connor | September 25, 2021

Fluids are the lifeblood of your car. They need to be as clean and fresh as possible to keep your vehicle running smoothly. While most people are familiar with getting motor oil changes, you might not be as well-versed in changing transmission fluid or why it is important. Knowing what this essential fluid does and when it should be changed can help you stay on top of your car’s maintenance.

Whether you have an automatic or manual transmission, rear-wheel, or front-wheel-drive car, you should know how to maintain it. Regular maintenance is one of the best ways to ensure that your vehicle stays running for longer and with fewer issues.

How Often Should You Check Your Transmission Fluid Level?

It’s a good idea to check all of your car’s fluid levels at least once a month. These checks include your engine oil, power steering fluid, brake fluid, coolant, and transmission fluid. Doing this regularly will keep you informed on the fluid health of your car so you can know whether or not you need to take it into a shop and get it looked at.

If you suspect that you have a transmission fluid leak, you can check the levels daily and keep a log of where they’re at as time goes by. You should not be losing a noticeable amount of fluid on a regular basis and if you are, this is a good indicator that you either have a leak or that the fluid is burning off. Either way, you will need to top off the fluid and make a service appointment for it to be diagnosed.

Why Check Your Transmission Fluid Level?

Checking your transmission fluid level regularly can give you a good idea of the condition of your vehicle's transmission. Ideally, you wouldn’t lose any transmission fluid and the level will remain the same until the next time it’s changed. Unfortunately, that isn’t always the case.

Transmissions can sometimes leak and this will require you to top off the fluid more often. If you are noticing red fluid on the ground after parking, you might have a transmission leak. Checking your fluid level regularly can help you know if your transmission is leaking.

How to Check Your Transmission Fluid Level

Checking the level of transmission fluid in your car is a simple process that anyone can do. Even if you’ve never opened the hood of your car, you can still check your fluids. If you make sure to do it properly, you can be certain that you’re getting an accurate reading.

1. Warm up the Engine
The temperature of your engine will change the level of fluid that the transmission dipstick shows. Fluids expand and contract with the heat level, so you’ll want to make sure they are in the condition they will be in when the car is running. Because of this, you should let the engine run for five to ten minutes before checking the fluid level.

Park your car on a completely level surface. It can be easy to check your fluid in the driveway and forget that the car is slanted. When this happens, all the fluid will drain to the back of the engine as it runs. This will give you an inaccurate reading on the transmission’s dipstick.

2. Remove and Wipe the Dipstick
After the car has warmed up, turn it off and locate the transmission fluid dipstick. This will be further down on the engine and closer to the back of the engine compartment than the oil dipstick, which is typically at the top. On some vehicles, it will be directed to the right of the oil dipstick. Be careful when reaching to grab the dipstick as the engine will be hot.

Wipe the dipstick with a clean rag and look at the markings. It will have two marks for “FULL.” One of them will be for when the engine is warm and one for when it is cold. You will want your fluid to reach the warm “FULL” mark.

3. Replace the Dipstick and Check Levels
After you have wiped down the dipstick, replace it in the dipstick hole. Pull it back out and check the levels. You may need to adjust the stick in the light to be able to see what mark the fluid comes up to. Be very careful because the transmission fluid on the stick will still be hot from the running engine.

4. Top Off If Needed
If your fluid level does not reach the “FULL” mark, you will need to top it off. Use transmission fluid that is suggested by your vehicle’s owner’s manual. This will be your best option if you aren’t sure what the difference is between types of transmission fluid.

Insert a long, thin funnel into the transmission dipstick hole. With that funnel, add transmission fluid slowly, checking the level as you go. Fill it until the fluid reaches the warm “FULL” mark. At that point, you will have enough fluid in the transmission and your gears will be lubricated properly.

How to Change Transmission Fluid

1. Warm up the Engine
The point of changing your transmission fluid is to completely remove the old, dirty fluid and replace it. Get all the old fluid out, it is best if the car is warm. This will heat the old fluid and make it much easier for it to flow out when you remove the transmission pan. Set the parking brake and run the car for five to ten minutes before getting it up on jack stands so you can get underneath it.

2. Remove the Transmission Pan
The transmission pan is located under the car towards the middle. Place a two-gallon plastic catch bucket underneath the transmission pan and start removing the bolts from one side. Be careful of any hot exhaust or engine parts.

3. Empty the Fluid
As you continue to remove all the bolts, the fluid will start to drain out of the pan. Once you have removed all of them, you will be able to completely disconnect the pan and dump the remaining fluid into your bucket. There is a gasket between the pan and the transmission that may need to be pried apart gently with a screwdriver.

4. Clean the Surfaces
Once you have drained the pan completely, clean off all the surfaces with a clean rag or paper towel. Inspect the area for any metal shavings or burnt smells. These could be signs that you need to schedule service for your transmission.

5. Replace the Filter
Your transmission has a filter to help remove impurities from the fluid and keep the chamber of the transmission clean. On most vehicles, you should replace this filter every time you change the fluid to make sure you get the most out of it. If you don’t replace the filter, you could end up with old impurities in the new fluid.

Some vehicles, however, use a wire mesh filter that doesn't need to be replaced. If this is the case with your vehicle, simply clean the filter out thoroughly (some experts recommend using a disc brake cleaner for this), and put it back.

6. Replace the Pan
Once everything has been cleaned and you have placed the new filter, put the pan back in place and bolt it back in. Don’t over-tighten the bolts as this could cause fluid to leak and make it more difficult to remove the pan the next time you want to do a fluid change.

Some vehicles have a replacable gasket around the seal of the pan to the vehicle. If yours does, replace the gasket at this time too.

7. Refill the Transmission Fluid
Refill the fluid through the dipstick hold in the engine compartment the same way you would when topping it off. Your owner’s manual will tell you how much fluid you need to completely fill the transmission pan. After refilling, start the engine and leave the car running while looking for leaks. If you see any, you may want to take your car in for a transmission service.

What is Transmission Fluid?

Transmission fluid is a lubricant that keeps the bearings and parts inside your car’s gearbox from grinding as they move. Without automatic transmission fluid, the gears would quickly wear down and expel metal shavings into the transmission. Fluid creates a liquid barrier between moving parts and keeps them cushioned.

Shifting gears is one of the most strenuous things your car has to do no matter what kinds of driving habits you have. There is a tremendous amount of pressure on the gears since they connect the engine to the wheels. Keeping your transmission lubricated is crucial and if your fluid isn’t clean, it can cause serious issues.

How to Choose a Transmission Fluid

If you aren’t sure what kind of fluid your transmission needs, you should always consult your car’s owner’s manual. It will not only tell you what kind of fluid you should be using, it will even tell you the best brand. The recommendation may also be printed on the dipstick. You should stick with the same kind of fluid that was included by the manufacturer or dealership. While most of these fluids are interchangeable, it is best to keep them consistent.

Changing Transmission Fluid Yourself vs. Having a Shop Do It

According to most manufacturers, you should change your transmission fluid once every 30,000 to 60,000 miles. This will keep the fluid from getting dirty and gumming up the gears, which can happen as the fluid heats up and cools down over and over again. You can either take your car into a shop to have them change the transmission fluid or you can do it yourself.

Most shops will charge somewhere between $80 and $250 for a transmission fluid and filter change. If you do it yourself, it should only be between $50 to $100 for materials like a plastic pan, new fluid, and a new filter. This doesn’t count the cost of tools and jack stands, which you will need if you’re going to change your own fluid.

Final Thoughts

Checking and changing your transmission fluid is an important maintenance step you can take for your vehicle. Transmission replacement is one of the most expensive repairs on your car, so keeping it in good shape is essential. By knowing how to check and replace your own fluid, you can save yourself even more money at the repair shop.