Inspection Express

How and Why You Should Check Your Transmission Fluid

Prevent expensive repairs with an easy routine inspection.

Most vehicle owners know that to keep their ride roadworthy, they need to stay up-to-date on routine maintenance, such as oil changes and tire replacement. But you should also keep tabs on your automatic transmission—you know, that thing with the gears that you shift into drive, reverse, and park multiple times a day. Keeping your transmission humming smoothly can pay dividends, as it’s one of the most expensive components on your car to repair or replace.

Thankfully, checking on your transmission’s health is neither as difficult, as time-consuming, nor as costly as you may think. Here’s how.

Checking the Fluid

Just as your engine uses oil to lubricate and cool its internals, automatic transmissions use specially designed transmission fluid for the same purpose. Conventional automatic transmissions, dual-clutch automatics, and continuously variable automatic transmissions each use a specific type of transmission fluid. If you’re unsure which fluid is used in your transmission, consult your owner’s manual; typically, transmission-fluid requirements can be found in the specifications section.

You don’t need to be a mechanic to gain insight into the condition of your vehicle’s transmission—a simple visual check will do. You’ll need to look at the level and condition of your transmission fluid.

Locate the Dipstick

First, locate the transmission dipstick, which can be found under the hood, in the engine compartment. Make sure you are locating the transmission dipstick and not the engine-oil dipstick; the transmission dipstick is usually further back in the engine bay, toward the firewall (the bulkhead at the front of the cabin). The transmission dipstick is typically marked with a specific color or a transmission symbol.

Note: if you can’t find the dipstick, don’t be alarmed. Many modern vehicles use a sealed-for-life transmission that never requires checking or fluid replacement—so they don’t have a dipstick. (Refer to your owner’s manual for your model’s specific service schedule and to double-check whether it has a transmission dipstick.)

If your vehicle has a sealed transmission, you can slam the hood shut and drive. But if your vehicle does have a transmission dipstick, here’s what to do next:

Check the Level

With the engine warmed up, leave the car idling in the park on a level surface. Pull out the dipstick, wipe it clean, replace it slowly, and then pull it back out. Check the fluid level—how high the fluid comes up on the dipstick—against the “full” and “low” or “fill” marks on the dipstick.


Fluid Condition

Now lay the dipstick on a white surface, such as a paper towel, to analyze the color of the fluid. The condition of your transmission fluid—and to some extent, the transmission itself—is indicated by the color of the fluid. If your fluid is healthy, it should have a reddish-pink color; if it’s getting to the point of needing replacement, it will be brownish-red. If the fluid is dark brown or black, then you may be replacing more than just your fluid. Dark fluid with a burnt smell is bad news; in the worst case, you might find fine metal shavings in the fluid as well. Both of those symptoms point to possible damage to your transmission’s internal components. This is usually a result of failing to follow the recommended service interval for replacing the transmission fluid, but it’s not impossible that transmission could have a premature mechanical issue, just like any other component on the vehicle.

Low Fluid?

If your fluid is low, it doesn’t necessarily mean you’re headed for disaster, but it does most likely mean there is a leak somewhere in the system. Filling up the transmission and then checking it daily to see how quickly the level goes down can be a good way to assess the severity of a potential leak. Also, try to visually inspect your transmission by looking under the car for any fluid oozing out of it. Does the car leave spots of reddish fluid on the ground after it’s parked? If the fluid is black, it’s engine oil. If it’s water, it’s likely condensation from the air-conditioning system.

If you do notice some transmission-fluid loss or observe that your transmission is using an abnormal amount of fluid, contact a mechanic as soon as you can.

Contrary to what some internet mechanics may tell you, a transmission-fluid replacement will not destroy an older vehicle’s aging transmission. Typically, when a transmission suddenly has issues after fluid replacement, it’s because there was already an internal problem, such as a worn clutch pack. If your transmission is healthy, then a fresh change of fluid will only help its longevity.

FYI, if your transmission fluid is low and needs topping off, this is usually done through the same tube that the dipstick fits in. Adding fluid (which is available at auto-parts stores) will require a funnel with a narrow—and most likely long—spout.

Just like any machine, a transmission needs proper maintenance to operate as the manufacturer intended. As they say, take care of your transmission, and it will take care of you.


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