Automatic transmission fluid color, along with other symptoms, can be an indication of an automatic transmission problem. The color of the transmission fluid alone, is NOT a reliable indicator. Transmission fluid color varies widely with modern fluid.  Darkening of fluid with age is also a normal characteristic. Knowing the normal color and looking for other symptoms can prevent being taken advantage of.

Several times a month, folks come in thinking they need automatic transmission repair. Sometimes repair is needed and many times it is not. Often, the reason they felt repair was needed is another shop told them the fluid was dark.  Transmission flushes are very profitable and fluid color may be used as an excuse to sell the service.

New automatic transmission fluid will have a bright to dark red, translucent color. The red color is the result of dye that is added to the fluid for identification. It is NOT an indication of the quality of the fluid nor the condition. An automatic transmission can have a significant amount of wear and still have clean red fluid.  It could also have dark fluid and still be in great condition.

Transmissions that have not been serviced, will benefit from a proper service.  The color of the fluid alone is not an indication of the need for service.  Many newer fluids are significantly darker than fluid of the past, even when new.  Color ranging between the first and second illustration are typical for new fluid.

Automatic transmission fluid tends to get darker, and more brown in color as it ages. This is normal and does not indicate a problem, in and of itself. The dye used in the fluid changes over time and color change is to be expected.

Heat also causes fluid to darken in color. A more reliable indicator of fluid condition is the time and mileage since the fluid and filter has been replaced. Automatic transmission fluid will last at least 30,000 miles and some fluid much longer, unless there are other problems. A proper service every two-years or 30,000 mile is more than adequate, with most transmissions.

Even very dark fluid, with no other systems or indicators does not mean there is a problem. Fluid that has not been replaced for 100,000 miles will often be very dark. The automatic transmission may also still be in good condition.

Restriction of the automatic transmission filter is much more of a problem than dark fluid. This is another reason why automatic transmission flushes are ineffective. Replacing dark fluid and not the filter will not help. With very dark fluid, it may also take more than one service for the color to return to normal.

Burnt fluid will be almost black and have a strong burned smell. If the fluid is burnt, simply changing it will do no good. Burnt fluid is a symptom and indicates other problems. The fluid is burned because a failure has occurred. A few possible causes include slipping clutches, a failing torque converter or bad solenoids. There will often be other symptoms, such as slipping. A proper diagnosis and repair can prevent further damage.

Transmission fluid color should always be considered along with other factors.  A trusted professional can let you know if there is a problem. 

Symptoms that point to a problem

 Slipping, improper shifting, noises or a warning light indicates a problem 

 Time and mileage are a better indicator of a need for service

 Simply flushing dark fluid is NOT a proper service

 All transmissions benefit from a proper service

Also see our article on Properly Checking Automatic Transmission Fluid

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