Transmission Fluid Colors and When You Should Worry

Transmission fluid does more than protect the transmission’s inner workings. It also helps your automobile shift gears. Low fluid can be disastrous. It can cause your transmission to overheat, slip out of gear, grind into gear, or damage the moving parts and gears. A transmission leak is also a bad sign. Not only does it mean your fluid is being reduced by the leak, but the color of your leaking fluid can signal serious transmission trouble. Here’s what we’re talking about here at Hummel’s Automotive Diagnostic & Repair.

Bright Red

When fluid is brand new, it is bright red. It’s easy to see through the red hue because the fluid is also translucent and feels slick to the touch. Bright red fluid does not need to be changed anytime soon. It’s good, but the fluid leak is a problem if you have one.


Red transmission fluid that’s lost some of its brightness does not need to be changed, either. As the fluid ages, it might not be as bright as it used to be, but if it’s still red and see-through, you’re still okay. The fluid can continue to protect the transmission and help it shift gears.

Light Brown

Light brown is also okay. You should plan to have the fluid changed soon, but if you can’t do so at the moment and you can still see through the light-brown fluid, you should be okay. Schedule a fluid check in the near future, however, to avoid waiting too long for the flush and refill.

Dark Brown

Once the fluid reaches brown or dark brown, it must be changed right away. This fluid is dirty and is no longer able to protect the transmission parts and gears. Dark brown fluid is also oxidizing, which is why it becomes opaque, i.e. you can’t see through it anymore.


If your fluid is black, it must be changed immediately. This fluid is damaging your transmission. It has oxidized and is no longer capable of lubricating the internal transmission mechanisms. In fact, it is depositing gunk onto your transmission gears.


Pink transmission fluid is also a sign of serious trouble. When transmission fluid is pink, it is actually red fluid diluted by your engine’s coolant. This is a sign of a serious leak between the cooling system and the transmission, and the diluted fluid will cause serious damage to your transmission.

Hummel’s Automotive Diagnostic & Repair in St. George, UT, can help. We can check your fluid every 30,000 miles to make sure it is still in good operating condition.

Photo by chat9780 from Getty Images via Canva Pro

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