When was the last time you checked your transmission fluid? If you answered “never,” don’t worry – you’re like most drivers!
Transmission fluid is a viscous fluid that lubricates and protects the internal components of a vehicle’s transmission. Many car owners neglect to check their transmission fluid regularly.
While most car owners know how to maintain their motor oil, many are unaware that they should regularly check their transmission fluid and schedule transmission fluid maintenance per manufacturer recommendations.
Checking the color of transmission fluid can indicate the state of the transmission. Transmission fluid should be bright red or slightly darkened, but if it is brown or black, it may indicate a problem.
If the transmission fluid is brown or black, it may need to be changed or flushed to prevent damage to the transmission.
Keep reading to learn more about why transmission fluid matters, what color should transmission fluid be and how to understand transmission fluid color.
What Is Transmission Fluid?
Transmission fluid is a specially formulated lubricant designed to protect your car’s transmission gears and clutch packs, enabling smooth shifts and preventing heat from destroying the fluid.
Transmission fluids are lubricants used in internal combustion engines, such as those found in automobiles. This fluid helps reduce friction between moving parts and reduce the amount of heat generated.
It also cools the transmission by transferring heat away from the transmission and other internal engine components. It is essential to check your transmission fluid level regularly and change it if it is low or begins to break down.
Types Of Transmission Fluids
Transmission fluid is an essential component of the vehicle’s transmission system.
Different transmission fluids are available; Dexron/Mercon and Multi-Vehicle Synthetic are the most common. CVT fluids require specific fluid, and Type Fs are not ideal.
Manual transmission, automatic transmission, automated manual transmission, and continuously variable transmissions require fluid types. A suitable automatic transmission fluid (ATF) is essential for optimal fuel economy and performance.
The Importance of Healthy Transmission Fluid
Transmission fluid plays a crucial role in the operation of your vehicle. It essentially hydrates your transmission to ensure it can go the distance. When the transmission fluid is lacking or compromised, it exhausts your transmission, and your vehicle may display signs such as:
- Lack of power
- Overheating
- Noisy while in neutral
- Puddles beneath your parked car
- Burnt odor
- Slipping, or trouble shifting gears
- Grinding or shaking feeling while driving
- Roaring noises
When left unattended, low or compromised transmission fluid can lead to extensive damage and costly repairs. Luckily, you can keep an eye on your transmission fluid by regularly checking its color. Let’s discuss how to evaluate transmission fluid color.
What Color Should Transmission Fluid Be?
Your transmission system goes through a lot during its lifetime. It is also made up of almost 1000 finely tuned parts, so you must keep it well-maintained.
One very useful indicator of the condition of your transmission is the color of the transmission fluid that keeps it lubricated and operating smoothly.
New transmission fluid is a bright, translucent and vibrant red color. When the transmission is in operation, its components get incredibly hot.
Transmission fluid prevents your transmission system from overheating and is very important for the overall performance of your vehicle.
If transmission fluid is not maintained correctly, leaks, overheating and other common transmission problems can result in a major fault and a repair bill totaling thousands of dollars.
Over time, due to contaminants flowing through the system and mixing with the fluid, the original bright red color can start to turn through a number of shades. A bright and deeper red color is normal, while a brown or burnt color is a good indicator that you need to arrange a transmission fluid change or flush.
Important Note of Transmission Fluid Color
While this guide refers to the common red transmission fluid traditionally used in vehicles, some manufacturers use different colored fluids. For example:
- Mercedes-Benz specifies blue ATF fluid for certain newer models
- Royal Purple brand ATF has a purple color
- HPL brand offers blue, green, and teal ATF fluids
- BG brand uses blue and yellow ATF
- Pentosin brand ATF is green
Always check your owner’s manual or consult your manufacturer to confirm the correct type and original color of fluid for your specific vehicle. The color changes described below will still help you identify potential issues, but you’ll need to use your fluid’s original color as the starting point.
How to Use This Information
To use the information and automatic transmission fluid (ATF) color chart provided below you must first determine the color of the transmission fluid that is in your transmission or transaxle. To do this, follow these instructions:
- Open your vehicle’s hood and locate the transmission dipstick.
- Pull the dipstick out of the filler tube.
- Determine the fluid color.
Look closely at the fluid on the end of the dipstick to determine the fluid color. If it’s hard to tell, place a few drops of transmission fluid on a clean white sheet of paper to get a more accurate color reading.
Match the color with the closest color shown on the fluid color chart below. The below provides an explanation and suggested course of action for each fluid color.
What Each Color of Transmission Fluid Means (Color Guide Chart)
Now that we know what a healthy transmission fluid color looks like, let’s discuss what other transmission fluid colors mean.
Red Transparent
What It Means: This is what new or like new transmission fluid should look like IF your vehicle uses traditional red ATF (please see note about transmission fluid colors above). As long as your fluid matches its original color, remains transparent, and doesn’t get low, your transmission is likely in good condition and unlikely to have a serious transmission problem.
Recommended Action: Check the fluid condition regularly and follow the manufacturer’s transmission/transaxle service procedures and service intervals.
Light Brown Semi-Transparent
What It Means: Your transmission fluid is in generally good condition. Some transmissions may naturally transition to this color over time without indicating a problem. Maintain this fluid condition and watch for leaks and your transmission will probably outlast the rest of your vehicle.
Why It Happens:
- Normal aging and heat cycles
- Regular transmission use
- Small particles from normal wear
Recommended Action: Check the fluid condition regularly and follow the manufacturer’s transmission/transaxle service procedures and service intervals.
Dark Brown Opaque
What It Means: Your transmission fluid is old, dirty, and contaminated and doesn’t provide adequate lubrication. Poor lubrication causes excessive wear and damage to internal parts. Dark brown transmission fluid also increases heat inside the transmission, which can quickly lead to transmission failure.
Note: Some vehicles may darken faster than others – sudden darkening is more concerning than gradual changes.
Why It Happens:
- Overdue fluid changes
- City driving with frequent stops
- Towing or hauling heavy loads
- High operating temperatures
- Accumulated debris from worn friction materials
Recommended Action: Take action now before this fluid condition causes serious problems or even transmission failure. Perform a transmission fluid and filter change or a complete flush of the transmission.
Very Dark Brown or Black
What It Means: The transmission fluid is old, dirty, contaminated, and/or oxidized. A burnt odor will confirm oxidization. Some high-mileage transmissions may have darker fluid while still functioning properly; sudden darkening is the main concern.
Why It Happens:
- Overheating
- Burnt fluid from excessive heat
- Metal particles from internal wear
- Long intervals between services
- Heavy-duty use without proper maintenance
Recommended Action: Take action immediately. Some internal damage may have already occurred. If your transmission is still working properly, a fluid and filter change or flush should be performed immediately. If problems already exist, a transmission rebuild may be necessary.
Light Pink
What It Means: When water or coolant has entered the transmission, the friction clutches fall apart and seals are ruined. Water enters the transmission through a damaged or leaking transmission cooler line in the radiator. This creates a high risk of transmission failure if not addressed immediately.
Why It Happens:
- Coolant mixing with transmission fluid
- Failed transmission cooler
- Cracked coolant lines
- Damaged radiator with internal leaks
Recommended Action: Unfortunately, you will need to rebuild or replace your transmission.
Other Ways to Check Transmission Fluid Condition
Fluid Smell
Smell the fluid. If it has a burnt odor, the transmission has overheated and the fluid is oxidized. The result is poor lubrication, increased friction, increased heat and excessive wear or damage to internal parts and seals.
In most instances, burnt smelling transmission fluid means some internal damage has already occurred.
Blotter Test
Place a couple of drops of the ATF on a paper towel and wait about 30-seconds or so. If the fluid has spread out and is red or light brown in color, the fluid is good – No action is needed.
If the fluid does not spread out and is dark in color, the fluid is oxidized. In this case, a fluid and filter change or flush is needed.
Warning Signs: Unusual Transmission Fluid Colors
Identifying unusual transmission fluid colors is crucial for catching potential issues early on. Here are some abnormal colors and what they might signify:
- Dark brown or black – If the transmission fluid is dark brown or black and accompanied by a burnt smell, it’s a good indication of overheating and the need for immediate attention.
- Milky appearance – A milky or foamy appearance may suggest water or coolant contamination, potentially signaling a leak between the transmission fluid and coolant systems. A common culprit here is a faulty radiator with an integrated transmission cooler.
- Cloudy or muddy fluid – This could be a sign of contamination with debris or particles, highlighting the need for a thorough inspection.
- Bright red with metal particles – If your fluid is a bright red color with visible metal particles, it could be a sign of internal mechanical wear. You’ll want to diagnose it right away.
Immediate action is crucial if any of these warning signs are detected. Ignoring these indicators could lead to severe transmission damage and costly repairs.
Common Causes of Discolored Transmission Fluid
Discoloration will happen over time, but it might not always happen normally. Understanding the common causes of discolored transmission fluid is essential for diagnosing potential issues. Some factors include:
- Overheating – Excessive heat can break down the fluid, causing it to darken and develop a burnt odor. In many cases, this is a signal that the transmission needs to be overhauled or replaced as the clutches have likely burned.
- Contamination – Contaminants such as dirt, debris, or coolant can alter the fluid’s color and compromise its effectiveness. A flush can sometimes be effective if the car isn’t exhibiting other symptoms of failure.
- Mechanical wear – Internal components wearing down can release metal particles into the fluid, leading to discoloration. When there’s metallic content you can see or feel in the fluid, it’s an indicator of a failure inside the transmission.
- Fluid breakdown – Over time, transmission fluid naturally degrades, resulting in a darker color. Regular fluid changes help maintain optimal performance.
How To Fix Transmission Fluid Problems
If your transmission fluid appears brown or black, you’ll likely need a transmission fluid change or flush.
A transmission fluid change involves draining dirty transmission fluid and refilling it with fresh fluid.
If you’re planning on changing your transmission fluid on your own, check the vehicle’s service manual to ensure you’re using the proper fluid. Adding the wrong product can damage your transmission.
Do note that transmission fluid changes can leave up to 30% of the old fluid in your transmission and compromise the fresh product sooner than necessary.
For this reason, some car owners prefer a fluid flush. A flush uses specialized equipment to clear out and clean your transmission, torque converter and cooler lines before adding fresh fluid.
Contact a transmission provider or your vehicle manufacturer if you’re unsure which service is best for you, or you aren’t entirely sure you need one. They’ll be able to point you in the right direction.