Although you may rarely think about it, transmission fluid plays an incredibly important role in maintaining your car’s health. Low or bad transmission fluid can severely damage your engine or transmission system, which means that you’ll have to shell out for some expensive repairs.
But it doesn’t have to get to that point. You can figure out on your own if its transmission fluid needs to be topped up or even replaced. Paying close attention to your car’s transmission fluid will not only save you money — it’ll also keep your car running smoothly for the foreseeable future.
What Is Transmission Fluid For?
Your car’s transmission system is a collection of gears. Automatic transmission systems switch between gears for you, while manual transmission systems require you to do the switching. Transmission fluid functions as a coolant and lubricant for your transmission system.
More importantly, however, transmission fluid acts as a hydraulic fluid. Hydraulic fluids like transmission fluid help transfer power — specifically from your car’s engine to its wheels. Without transmission fluid, your car wouldn’t be able to run effectively, or even at all!
What Are the Symptoms of Low or Bad Transmission Fluid?
Whether your car is manual or automatic, bad or low transmission fluid will undoubtedly cause problems. Some of these problems are obvious, while others may be harder to detect.
With a bit of vigilance, you’ll be able to recognize these 7 symptoms of low or bad transmission fluid.
#1 Problems with Changing Gears
The most obvious sign that your car’s transmission fluid is low or bad is if your vehicle has problems related to changing gears. Because transmission fluid is a vital part of gear-changing, it’s almost guaranteed to cause issues if it’s leaking or tainted.
If your car has a manual transmission system, it won’t be difficult to recognize issues with changing gears. Even with automatic systems, knowing what to feel and listen for can save you and your car a lot of heartbreak.
Grinding or groaning sounds
Even if you don’t know its language, your car communicates with you via the sounds it makes. Sound can be a vital means of discovering problems with your car’s transmission fluid.
If you hear grinding or groaning noises in your car, especially while switching gears, it may be time to replace the transmission fluid. That noise isn’t just irritating — it’s a cry for help from your car!
Transmission fluid ensures that your car’s gears maintain safe contact with one another. Without proper lubrication, metal gears can seriously damage each other. Keep running your car like that for too long, and you’ll have to replace its entire transmission system.
Problems with transmission fluid aren’t always audible — sometimes, they’re tangible. If your car has a manual transmission, you know how it “feels” to switch gears. Even if you drive automatic, paying attention to how your car feels could save your car from serious damage!
“Transmission slipping” happens when your car doesn’t stay in gear. After you switch from one gear to another, your car’s transmission will “slip” back to the previous gear. You may be able to feel the slip as a “popping” sensation. Alternately, you could feel it in the form of your wheels getting less power than they should.
No matter how you feel it, transmission slipping is dangerous. Low or bad transmission fluid is often the culprit, since gears have trouble switching back and forth without the right hydraulic pressure. If you experience transmission slipping, check your transmission fluid right away!
Gears don’t change smoothly
Your car’s transmission doesn’t need to slip in order to indicate problems with transmission fluid. Pay attention to jerky or jumpy gear changes — low or bad transmission fluid might be at fault.
The same goes for delays in gear changes. Does it take a few seconds for your transmission to switch from Drive to Reverse? Transmission fluid could also be responsible for gears changing slowly. The change should happen almost instantly — if it doesn’t, then your car’s transmission fluid is due for a checkup.
#2 Changes in RPM
Your car’s wheels’ RPM, or rotations per minute, is directly related to your car’s transmission system. As RPM increases, the transmission must switch to a higher gear. Sudden changes in RPM point to transmission problems, which often stem from low or bad transmission fluid.
If your car’s RPM changes suddenly, you’ll be able to hear and feel it. An increase in RPM will make your car sound louder and feel less powerful. When the RPM changes, it’s a clear symptom of something wrong with your car’s gears — and a sign that you should check your car’s transmission fluid.
If you’ve ever seen smoke pouring out from under the hood, then you know it’s a scary experience. The same goes for catching a whiff of a burning smell from your engine. Smoke or a burning smell coming from your car could indicate that your transmission fluid is low or bad.
When you drive with low or bad transmission fluid, your car’s transmission system can overheat. Gears that rub together without lubrication create friction. This friction then produces heat, which can ruin the transmission system.
If you detect any burning odors or see smoke coming from your car, stop driving immediately! You could not only damage your car — you could also put your safety and the safety of your fellow drivers at risk!
#4 Engine Light On
Your car’s engine light can be a tricky thing to understand. When the engine light comes on, you shouldn’t ignore it — it could indicate any number of different problems. One of these issues, as you’ve probably guessed, could be bad or low transmission fluid.
#5 Red or Brown Spots on the Driveway
Are fluids leaking from your car? If so, putting cardboard down in your garage isn’t enough to solve the problem. You need to figure out what’s leaking, and put a stop to it! It could be oil, brake fluid, or transmission fluid.
Determining what kind of fluid is leaking from your car isn’t difficult — check the fluid’s color. If the fluid is red, brown, or a reddish-brown color, then you can be sure that it’s transmission fluid. No matter the color, you’ll need to fix the leak ASAP!
#6 Fluid Color Is Wrong
Transmission fluid’s color is its most obvious indicator of quality. If your car is experiencing transmission problems, but the fluid level is fine, then a color check is definitely in order.
Normal, clean transmission fluid is clear with a light red color. If your car’s transmission fluid is dark red and a bit cloudy, don’t panic — it could just be a little old. Older transmission fluid isn’t necessarily bad, but you should check it regularly since it may need to be replaced in the near future.
If your car’s transmission fluid is dark brown or black and opaque, that’s a sure sign that it’s gone bad. These colors indicate that the fluid has been contaminated and should be replaced as soon as possible.
Sometimes transmission fluid can be more pink than red, but still clear. If your car’s transmission fluid is pink, it’s probably been tainted by water or coolant from elsewhere in your car. Like brown or black fluid, you should replace pink fluid before it damages your car.
#7 Car Won’t Run
Sometimes it’s possible to ignore your car’s warning signs before it’s too late. Other times, car problems don’t reveal themselves until the breaking point. When your car doesn’t run, there’s no denying it — you’re dealing with a serious problem!
Note that I say “when your car doesn’t run,” not when it doesn’t start. If your car’s transmission fluid is low or bad, it won’t prevent your car from starting. It can, however, prevent your car from running.
As I’ve described in detail above, low or bad transmission fluid can severely damage your car’s transmission system. If that damage gets bad enough, your car won’t run — even if you put it into gear.
Hopefully, however, you won’t let it come to that! Now that you know the main symptoms of low or bad transmission fluid, you should be able to identify problems before they get out of hand. And if you suspect any transmission fluid problems but want to make yourself certain, read on.
How to Check Your Car’s Transmission Fluid
If your car is experiencing any of the problems listed above, it’s a good idea to check your transmission fluid as soon as possible. Depending on your car model, it may not be possible to check at home without the right equipment. However, if you can check on your own, here are the 4 easy steps to checking for low or bad transmission fluid.
1. Find Transmission Dipstick
Many cars have dipsticks which allow you to check different fluid levels. Most people are familiar with oil dipsticks. However, you may not know how to find your car’s transmission fluid dipstick.
When looking for your car’s transmission fluid dipstick, check for a written label on the cap. If it doesn’t have a label, then check your car’s manual to see where it might be. Don’t start twisting random knobs if you don’t know what they do!
Video below shows one way to find your car’s transmission fluid dipstick.
Newer car models, however, might not have a transmission dipstick. If that’s the case, the process is more involved. You might even need special tools that aren’t readily available to consumers. If your car’s transmission doesn’t have a dipstick, then I suggest taking it to a qualified mechanic to have your transmission fluid checked.
If your car does have a dipstick — great! But don’t take it out just yet. We’ll get there soon enough.
2. Start the Engine and Let It Idle
Before checking your car’s transmission fluid, you need to start your engine. The reason for this is that transmission fluid needs to be at a certain temperature before it can be checked. The temperature should be around 103℉.
It might not be possible to check the transmission fluid’s temperature. Nevertheless, letting your car run idle for a few minutes should heat it up sufficiently. Leave your car in park throughout the process — there’s no need to switch gears.
3. Check Dipstick
After you’ve let your car idle for a few minutes, you can remove its transmission fluid dipstick. Leave the car running while you do this — it’s perfectly safe, and you won’t be sprayed by any hot liquids!
The transmission fluid dipstick will have a section near its tip that indicates the fluid level. It may be labeled “MIN” and “MAX,” or it could simply have a cross-hatched section. Either way, the fluid should be somewhere within the designated section. If it’s below the minimum line or close to it, it could be time to replace your car’s transmission fluid.
4. Test Color and Odor
Even if the levels look fine, there’s still one more test you should do. Remember how I mentioned that transmission fluid’s color is important? Before putting the dipstick back, it’s always a good idea to check the fluid’s color.
Some people recommend rubbing the fluid between your fingers — I don’t recommend that! There’s an easier way, which is also more accurate. Simply wipe the dipstick with a clean, white paper towel. Remember — your car’s transmission fluid should be red and clear.
There’s one final thing you should do, even if the transmission fluid is a good color. Give the paper towel a sniff! If your car’s transmission fluid is fine, then it should smell slightly sweet. Bad transmission fluid will have a burnt smell.
So you’ve diagnosed your car’s problems and checked your transmission fluid, and you know that the fluid’s at fault. What should you do next?
Well, you can check out my guide to the best transmission fluids that is linked above. These will serve as worthy replacements for low or bad transmission fluid. Best of all, they’ll protect your car from damage and have it running like new!