What Is the Purpose of Automatic Transmission Fluid?
Transmission fluid is a thick oil that lubricates the moving parts inside your transmission, which minimizes the friction between these moving parts and allows heat created by friction to dissipate rather than build up. Automatic transmission fluid is used specifically for automatic transmissions, in which it “provides hydraulic pressure and friction to make the internal parts work,” writes the Universal Technical Institute.
Why Is It Important to Change Your Transmission Fluid?
Everyone knows how important it is to change your car’s oil regularly, but there’s less awareness of the importance of changing your automatic transmission fluid. As FIXD puts it, “In the same way that your oil is the lifeblood of your engine, the transmission fluid is the lifeblood of your transmission.” It’s crucially important to the operation of your car–if you don’t, metal shavings and other debris can build up in the fluid, and it can even “seize, evaporate, seep out, and cause catastrophic transmission failure” (source: The Drive).
Replacing your car’s transmission could cost thousands of dollars, so keeping your transmission in tip-top shape by changing the fluid at recommended intervals (more on this in the next section) is a must.
How Often to Change Automatic Transmission Fluid
As a general rule, automatic transmission fluid must be changed once every 60,000 to 100,000 miles. If you’re uncertain about how often to do so, check your car’s maintenance schedule, which should be included in the owner’s manual.
Signs That You Need to Change Your Transmission Fluid
Here are some of the most notable signs to look out for that indicate you have low transmission fluid:
1. Transmission fluid color/smell
The dipstick (which will most often have a red handle) shows that the automatic transmission fluid is dark and discolored or smells burnt. When transmission fluid is new, it’s bright red or green, turning darker brown as it ages.
2. Transmission sounds/shifts
You notice that the transmission is especially loud (making grinding sounds in particular) or shifts roughly.
3. No drive engagement
When you’re in the reverse or forward gears, there is a lack of drive engagement.
4. Burning smell
If you smell burning while your car is driving, this is a sign that your transmission’s parts are experiencing friction.
5. RPM spikes
RPM (revolutions per minute) spikes before shifting gears.
6. Stuck in a gear
Your transmission is getting stuck in one gear.
How to Change Automatic Transmission Fluid
Note: Please keep in mind that this is an intermediate-level DIY auto maintenance project, so it’s not for everyone. If you’re not confident or experienced when it comes to car maintenance, we recommend leaving this task to a professional.
1. Gather all the necessary tools and materials:
- Car jack
- Transmission fluid
- New transmission filter (optional)
- New transmission filter O-ring/gasket
- Transmission drain pan
- Wheel chocks
- Wheel ramps
- Socket wrench
- Crescent wrench
- Safety glasses/goggles
- Tarp, newspaper, or cardboard to protect the ground
2. Warm up your car by driving it for about five or ten minutes–this will warm up your transmission fluid and cause it to flow more easily. Then allow your engine to cool off a bit for five or ten minutes before beginning to work because you also don’t want to be working with extremely hot fluid and components.
3. Locate a flat, level surface such as a garage or driveway, and park your car there with the parking brake on. Be sure to remove your keys from the vehicle when you do this and keep them in a safe place.
4. Jack up your car and use the wheel chocks behind the back tires to keep it in place as you work on it. You can also drive it onto steel wheel ramps if you have them and find them easier to work with.
5. Lay out some barrier such as a tarp, some newspaper, or a piece of cardboard to protect the ground below your transmission. This is a good backup in case you spill a bit of transmission fluid while changing it.
6. Get under your car and find the transmission fluid pan. Here are a couple of rules of thumb for locating this pan:
- If you have a front-wheel or four-wheel-drive vehicle, the transmission fluid pan is most likely to the right or left of the engine bay.
- If you have a rear-wheel-drive vehicle, it will probably be situated somewhere under the center console.
- If you can’t locate it using these guidelines, check your car’s manual for specific guidance.
7. Once you’ve located the transmission fluid pan, look to see if there’s a drain plug or if (more commonly) you’ll need to remove the whole pan to empty it out. If it’s the latter, you’ll need to make sure your drain pan is wider than the transmission fluid pan to ensure you don’t leave a big mess behind.
8. Safety first: don your personal protective equipment before you start the actual process of replacing the transmission fluid. Gloves and eye protection are the most important for this task.
9. If you have a drain plug, remove it and let the old fluid drain out. If you don’t, remove the whole transmission pan by loosening the bolts at one end of the pan with a crescent or socket wrench, and catch the fluid that comes out.
Continue to loosen the bolts on either side and allow the fluid to drain until you have removed all the bolts and the pan has been removed. Set the pan and its bolts aside and inspect the drain pan to see if there are any large pieces of metal, which can be a sign of damage to your transmission.
10. Once you’ve removed the transmission fluid pan, check the transmission fluid filter for any damage and replace it if needed. You don’t need to replace it every time you change your transmission fluid, but it is always a good idea to check it.
11. Replace the transmission filter O-ring/gasket and make sure it seals, and use an oil-soluble grease–rather than gasket sealer or adhesive, which are both no-nos in this situation–to make sure the new gasket is sealed to the pan.
12. After you replace the filter, it’s time to put the transmission fluid pan back on (and put the drain plug back, if it has one). Align the pan with the pattern of the bolts and hand-tighten them so that the pan stays in one spot while you tighten the bolts with a socket/crescent wrench. Don’t tighten them too much, or you risk causing damage to the pan.
13. Now it’s time to add the new transmission fluid. Take your car off the jack or the wheel ramps and allow it to rest directly on the ground. Open your car’s hood and look for the red dipstick of your transmission fluid port. Insert a funnel into the port to ensure all the transmission fluid makes its way into the port and doesn’t get on other parts of the engine.
14. Close the hood, turn on and run the car for a few minutes, and turn it back off. Then check the transmission fluid dipstick to confirm that you’ve added the right amount of fluid. If the level is too low, now is the point when you can add more.
15. It’s crucial to make sure there are no transmission fluid leaks before you start driving again. Place a fresh piece of cardboard underneath the transmission fluid pan while running the car in one spot. Then check the cardboard to see if any fluid has leaked out onto it. If so, you may have to tighten the bolts up some more, replace the gasket on the transmission fluid pan, or, if it turns out the pan is damaged, replace it with a new pan.
16. Finally, we implore you to dispose of used transmission fluid correctly so that it doesn’t end up in the environment, where it can cause harm to plants, animals, and ecosystems. If you’re unsure how to do that, here’s a helpful guide to safely disposing of various automobile fluids from the Rislone blog.
How Much Does It Cost to Change Automatic Transmission Fluid?
Changing your automatic transmission fluid yourself will cost you an estimated $51 to $100 (source: Family Handyman).
Compare this to the price of having someone else do it, which might cost you anywhere from about $150 to $200, on average. Learning to change your transmission fluid could save you about $100 to $150 per change. This adds up to as much as $1,050 over the life of your car if you change it every 30,000 miles (the average car lasts up to 200,000 miles, according to Progressive). This certainly makes it a worthwhile DIY if you feel up to the task.
Automatic Transmission Fluid Products We Recommend
Investing in a quality transmission fluid can help to preserve the function of your transmission, which means it could help save you thousands of dollars on transmission replacement costs. Here are the top three brands of automatic transmission fluid:
This isn’t the cheapest product of its kind on the market, but it’s a high-quality option with low co-efficient friction and high film strength, meaning it lowers heat and wear on your transmission. Another feature that sets this product apart is its oxidative stability, which is higher than that of other brands, which means the Royal Purple transmission fluid performs well for longer.
It’s also convenient that Max ATF is compatible so that you can mix it with other automatic transmission fluids without problems. One reviewer comments that Royal Purple “has been making lubricants for $1,000,000+ industrial transmissions for years, and it shows.” Another writes that they’ve been using it in their cars, “and the transmissions love it, it shifts smooth, accurate and better temperature control.”
Valvoline is known for being “America’s first motor oil brand,” and its reputation is well-earned. In addition to providing “consistent shift performance for new and old GM transmissions,” it has several benefits: extending the life of the transmission fluid, preventing the fluid from breaking down when the operating temperature climbs, and minimizing the build-up of varnish and sludge.
Like Royal Purple’s automatic transmission fluid, Valvoline’s product also has higher oxidative stability than many other products on the market. One reviewer even writes that this is “the only real “full synthetic” Mercon LV available.”
Just because this product is a more affordable option than others on this list doesn’t mean you’re sacrificing quality. It does a great job of protecting the transmission in periods of extreme heat or cold (all the way down to -54 degrees Celsius), extending the life of the transmission by reducing wear. Mobil’s automatic transmission fluid also keeps the transmission clean, effectively minimizing oil breakdown and deposits.