How to check transmission fluid and why you should check it

How to check transmission fluid and why you should check it

Most car owners know that in order to keep their car roadworthy, they need to stick to routine maintenance such as oil changes and tire rotations. But you should also keep an eye on your automatic transmission-you know, the thing you shift into drive, reverse, and park multiple times a day. Keeping your transmission running smoothly can pay dividends, as it’s one of the most expensive parts on your car to repair or replace.

Thankfully, checking the health of your transmission isn’t as difficult, time-consuming or expensive as you might think. The methods are listed below.

Check the Fluid
Just as an engine uses oil to lubricate and cool its internals, an automatic transmission uses specially designed transmission fluid for the same purpose. Conventional automatics, dual-clutch automatics, and continuously variable automatics all use a specific type of transmission fluid. If you’re not sure which transmission fluid to use in your transmission, consult your owner’s manual; usually, transmission fluid requirements can be found in the specifications section.

You don’t need to be a mechanic to know the condition of your vehicle’s transmission, just perform a simple visual inspection. You need to check the level and condition of the transmission fluid.


Find the dipstick
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Automobile and Driver
First, locate the transmission dipstick, which can be found under the hood. Make sure you find the transmission dipstick, not the oil dipstick; the transmission dipstick is usually further back in the engine compartment, toward the firewall (the bulkhead at the front of the cabin). The transmission dipstick is usually marked with a specific color or transmission symbol.
Note: If you can’t find the dipstick, don’t panic. Many modern vehicles use sealed-for-life transmissions that do not require fluid checks or changes and therefore do not have a dipstick. (Refer to your owner’s manual for your model’s specific maintenance schedule and double-check that it is equipped with a transmission dipstick.)

If your vehicle is equipped with a sealed transmission, you can close the hood and continue driving. But if your vehicle is equipped with a transmission dipstick, the next thing to do is to check the fluid level:

Checking the Oil Level
After the engine has warmed up, park the vehicle on a level surface and idle it. Pull out the dipstick, wipe it clean, replace it slowly, and then pull it out again. Check the oil level against the “full” and “low” or “topped off” marks on the dipstick – how high the oil level is on the dipstick.

You can tell the health of your car’s transmission by the color of the transmission fluid.

Oil Condition
Now place the dipstick on a white surface such as a paper towel and analyze the color of the fluid. The color of the transmission fluid can indicate the condition of the transmission fluid and to some extent the condition of the transmission itself. If the transmission fluid is healthy, it should be pink; if it has gotten to the point where it needs to be changed, it will be a brownish-red color. If the fluid is dark brown or black, you may need to change more than just the oil. Dark-colored oil with a burnt smell is bad news; in the worst case scenario, you may find tiny metal shavings in the oil. Both of these symptoms indicate that the internal components of the transmission may have been damaged. This is usually caused by failing to change the transmission fluid at the recommended service intervals, but the transmission can also experience premature mechanical failure, just like any other part of the vehicle.

Too little oil?
If the fluid is too low, it doesn’t necessarily mean you’re headed for disaster, but it probably means there’s a leak somewhere in the system. Filling up your transmission and then checking the rate at which the level drops each day is a good way to assess the severity of a potential leak. Additionally, you can visually inspect the transmission for fluid seepage by looking underneath the car. Does the car leave some light red fluid on the ground when you park it? If it’s black fluid, it’s engine oil. If it’s water, it could be condensation from the air conditioning system.

Oil stains on the road
If you do notice some loss of transmission fluid, or an abnormal amount of transmission fluid, contact a mechanic as soon as possible. We recommend that you first visit a reputable auto dealer for vehicle sales and repairs. Their service department has the most experience with your make and model and may have encountered this problem before. If you can pull over and wait for an inspection, do so.


Contrary to what some internet mechanics may tell you, changing the transmission fluid will not ruin the aging transmission in your old car. Typically, if a transmission suddenly develops problems after a fluid change, it’s because there’s already an internal problem, such as a worn clutch pack. If your transmission is healthy, then a refill will only extend its life.

Incidentally, if the transmission fluid is low and needs to be refilled, it can usually be done through the tube where the dipstick is located. Adding fluid (which can be purchased at an auto parts store) will require a narrow-mouth funnel and most likely a long-mouth funnel as well.

Just like any machine, a transmission requires proper maintenance to operate as the manufacturer intended. As the saying goes, take care of the transmission and the transmission will take care of you.

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