DIY

How to Check Automatic Transmission Fluid

Reading Time: 4 minutes

Checking automatic transmission fluid (ATF) used to be a straightforward affair—but not anymore. These days, because so many cars no longer have a transmission dipstick, the process can be complicated.

On many modern cars, you must go underneath the vehicle and remove a plug to check the ATF. What’s more, some transmissions now require a scan tool to check the fluid level.

There are also some transmissions that are completely sealed, without any means for inspecting the fluid.

So, how do you approach the potentially cumbersome process of checking the ATF in your car?

car with automatic tranmission
These days, because so many cars no longer have a transmission dipstick, checking ATF can be a complicated process.

How to Check Automatic Transmission Fluid (If Your Car Has a Dipstick)

Because checking transmission fluid can be complicated, before doing anything else, you should consult your owner’s manual. The document will usually have instructions for checking the ATF if the process is straightforward.

On the other hand, if the owner’s manual doesn’t list a procedure, checking the ATF is either some complex ordeal or the transmission is completely sealed.

To find out more, consult a repair manual. You may also be able to call your local dealership for the recommended inspection procedure. A Google search can also be useful, though you should always be cautious of free online resources—be selective of which ones to trust.

Checking Automatic Transmission Fluid: A Step-by-Step Guide

Even if your car has a dipstick, it’s a good idea to consult the owner’s manual before checking the ATF. There are often discrepancies in the fluid-checking process.

For example, while the fluid level is typically checked while the engine is running, on some vehicles (certain Hondas come to mind), the engine must be off. Also, some automakers recommend checking the ATF level with the transmission in neutral, rather than park.

That’s why it’s important to double-check the recommended service and safety procedures before digging in.

If your car has a dipstick, here’s a general outline for checking the ATF:

1. Park the vehicle on a level surface.

2. With the transmission in park, start the engine and allow the transmission to reach operating temperature. This step is critical because ATF expands as temperature increases. You may need to drive the vehicle several miles to get the transmission warmed up properly.

3. Set the parking brake and apply the brake pedal. Then, move the gear selector from park, through the entire gear range, then back to park again.

transmission fluid dipstick location
Be sure not to confuse the transmission dipstick with the engine oil dipstick.

4. Locate the transmission dipstick (be sure not to confuse it with the engine oil dipstick).

5. Remove the dipstick and wipe it off on a clean rag.

wiping dipstick with a rag
Wipe the dipstick off a clean rag, reinsert it, then remove it again to check fluid level.

6. Reinsert the dipstick, then remove it again to check the fluid level.

7. Typically, the fluid should be within the crosshatch pattern if the level is correct.

In addition to checking the level, you should note the condition of the fluid. Most vehicles use ATF that is red or pink in color. If the fluid appears light brown, it’s overdue for service.

Fluid that is black and/or smells burnt indicates an internal transmission problem.

Typically, the fluid should be within the crosshatch pattern if the level is correct.

What to Do If You Find Problems with Your Automatic Transmission Fluid

Most engines will consume (burn) a small amount of oil over time—but transmissions do not consume ATF. If the transmission fluid level is low, there’s a leak somewhere.

Areas that commonly develop leaks include the transmission pan, axle seals, cooler lines, and torque converter (aka front pump) seal. Inspect the unit for leaks (or have a professional inspect it for you) and perform any necessary repairs.

And what if you find that the fluid is dirty? Dirty fluid, which is light brown in color, usually indicates that your car needs a transmission service. The procedure is considered routine maintenance and should be performed per the manufacturer’s maintenance schedule.

mechanic checking car
Inspect your car for leaks and make sure to regularly perform routine maintenance.

Check out our article on how to change automatic transmission fluid if you’re interested in doing the job yourself.

Should you find the fluid is black and/or smells burnt, chances are, the transmission is suffering from internal problems. Take your car to a professional for proper diagnosis and repair.

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Author

Mia Bevacqua

Chief Mechanic at CarParts.com

Mia Bevacqua is an automotive expert with over 15 years of industry experience. She holds ASE Master, L1, L2, and L3 Advanced Level Specialist certification, as well as a bachelor's degree in Advanced Automotive Systems.

Throughout her career, Mia has applied her skills toward automotive failure analysis inspections, consulting, diagnostic software development, and of course, freelance writing. Today, she writes for companies around the world, with many well-known clients showcasing her work.

Mia has a passion for math, science, and technology that motivates her to stay on top of the latest industry trends, such as electric vehicles and autonomous systems. At the same time, she has a weakness for fixer-upper oddballs, such as her 1987 Chevy Cavalier Z-24 and 1998 Chevy Astro Van AWD.

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