The color of transmission fluid (typically red or green) is the result of a dye that is added to help you distinguish it from other fluids in your car such as engine oil, power steering fluid, brake fluid, and antifreeze. It can also give you an idea of the fluid’s condition and tell you that it needs to be changed. Let’s find out how…
Note: While not as common, transmission fluid can also be other colors such as blue and yellow.
Note 2: Certain windshield wiper and antifreeze fluids can be red, so make sure you always read the label first!
While off-color fluid can point to a potential transmission problem, the color should not be the only reason a shop gives you as proof that you need to get a transmission flush or repair/replacement (which are both very profitable for them). An old, worn our transmission can have clean, red fluid and a brand new transmission can have dark fluid. The color doesn’t mean much when taken out of context.
Several other symptoms should also be apparent when a real problem exists. The fluid alone cannot diagnose a problem and be used to prescribe a particular (likely unneeded) service – be wary of a shop that thinks otherwise.
What color is clean/new transmission fluid?
When the fluid is new, it has a translucent red color. It may be hard to see on the dipstick, but if you wipe it on a clean white rag, it will appear bright to dark pink/red.
Here is how to check your transmission fluid.
The color will change over time as it ages, is subjected to heat and friction, and collects contaminants (dirt and debris). It typically starts out bright, translucent pink/red and slowly transitions to a darker, more brown and more opaque color until it appears black. This process is completely normal and does not mean there is a problem.
Manufacturers use a number of different chemical compounds, resulting in the various kinds of fluid available (ie. Dexron, Mercon, ATF+4 etc). Each type is formulated to work with a particular series of transmissions and can have a slightly different opacity and tint when new compared to other brands.
A good indicator that it’s time to change your transmission fluid is the mileage and time since it was last done, but in general, the darker/more opaque the fluid is, the sooner it needs to be changed again.
Under regular driving conditions, the fluid should be changed every 2 years or 30,000 to 50,000 miles, whichever comes first. Heavy-use commercial vehicles such as those used for hauling or towing run much hotter so they should be serviced more frequently.
What color is worn transmission fluid?
As fluid flows around the internal parts of a transmission, it absorbs the heat that they create. It then travels to the front of the engine compartment and passes through the radiator, where it expels the heat and cools down before returning to the transmission.
Over time, this process will cause the fluid to darken from bright, translucent red to a dark red and eventually to a brownish color. This means that the chemical composition of the ATF is starting to break down, reducing its ability to remove heat from the transmission and lubricate its moving parts.
It is important to note that some fluid is left trapped in the torque converter when the fluid is drained. This old fluid mixes with the new fluid that is added and can give it a brownish tint – even though the majority of the fluid is brand new.
What color is dirty transmission fluid?
Age and high temperatures can turn the normally reddish colored fluid to black. This may indicate that the fluid’s heat removing properties are severely compromised, and it may not be able to effectively protect the internal components from excessive wear and tear. However, as mentioned previously, the color alone does not mean there is a problem unless other symptoms are present. What’s most important is that the filter is changed regularly so that it does not become clogged and restricted.
Burnt transmission fluid
If the fluid is black and has a burned smell, it indicates that it is no longer removing all the heat from the transmission or lubricating the internal parts properly and more than likely, the transmission has suffered some internal damage.
If this is the case, look for metal shavings in it by dropping the transmission pan. Some metal shavings should be expected, but a significant amount of debris could indicate severe internal damage, in which case you should have it serviced as soon as possible. This is one of the most common symptoms of a transmission problem. Unfortunately, changing the fluid usually won’t have much of an effect at this point, so it’s important to make sure that your fluid never gets to this stage. If not dealt with, the transmission will eventually fail, leaving you with the options of getting it repaired, replaced or buying a new car.
A malfunctioning torque converter, failing solenoids and slipping clutches can also cause the symptom of burnt transmission fluid. Hard shifts and slipping when changing gears are symptoms that are often present at the same time as burnt fluid.
Water or coolant in the fluid
If it appears to be foamy, has lots of air bubbles or it looks thin (more fluid on the dipstick the normal), then there may be coolant or antifreeze leaking into your transmission fluid.
If a significant amount of water gets into a transmission due to flood/high water or a leak, rust will develop and the transmission will fail.
This problem can be caused by a blockage or leak in the cooling lines on the radiator. If coolant leaks into the fluid, it won’t be able to lubricate the moving parts properly. The chemicals in the anti-freeze can also cause severe damage to the internal components of a transmission. To fix this problem, the leak/blockage will have to be addressed, and the filter/fluid should be changed as well. If a significant amount of foreign liquid got in, the transmission may have to be rebuilt with new components to replace those that were damaged.
Over to You
What is the color of your vehicle’s fluid? If you have a question, let us know in the comments and we’ll do our best to help you out.