Transmission fluid is crucial for your engine’s transmission system to be properly lubricated. Water entering the transmission fluid can cause many issues in the transmission system.

The friction lining of the clutch plates and the metal parts may corrode due to water in the transmission fluid. The transmission system can sustain damage from even a small amount of water.

Even one start of the vehicle while the transmission fluid still contains water can lead to rust, adhesive loss in the clutch, and other transmission problems. 

We’ll examine some of the reasons why water gets into the transmission fluid in this article. Let us first discuss what will happen if water gets mixed with transmission fluid.

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What happens if water gets in transmission?

The following question determines the amount of damage caused by water in transmission fluid.

  • How much water has been mixed with the fluid? Check the transmission fluid levels properly to know how much damage was done.
  • How many miles have you driven with water mixed in with the transmission fluid?

When water droplets leak into the fluid, it typically turns a milky pink color. If the fluid is gray, a large amount of water has mixed with it.

If you have been driving the car after it has been contaminated with water, chances are that some damage has already taken place. 

Older transmissions are not as affected by less than or equal to 100 ml water, but modern transmissions can suffer serious harm even from small amounts of water.

  • Water in the transmission fluid can cause corrosion in transmission metal parts. 
  • Fluids mixed with water can also accumulate in transmission channels and form sludge.
  • Water can also contaminate friction plates, causing problems with gear shifting.
  • If water has been mixed with transmission fluid for a long time, the adhesion of transmission parts will also be affected.

Causes of water in transmission fluid

Here are some of the reasons why water gets into transmission fluid:

Coolant leak

The radiator aids in heat transfer from the transmission fluid to the coolant. The cooling line connects the radiator to the transmission. The hot transmission fluid cools down in the small passage of the radiator. 

The coolant and transmission fluid can mix if the passage is broken due to a rupture in the internal radiator tank. You may have to pay between $100 and $500 to fix the transmission’s cooling line. 

Moisture on the Transmission Dipstick

The transmission dipstick is used to check the fluid level in the transmission. There is a chance that water or moisture will get on the dipstick during engine cleaning or due to rain. The transmission dipstick is located near the transmission system in the engine’s rear end. 

Water particles can get mixed with transmission fluid if moisture is on the dipstick. To avoid this, clean the dipstick with a clean, dry cloth in case it gets wet.

Improper Driving

Driving in off-road conditions, floods, or heavy rain can allow water to enter the engine. If the engine is surrounded by too much water, some of it may enter the transmission reservoir and mix with the fluid.

How to Get Water Out of Transmission Fluid

After talking about the cause of the water getting into the transmission fluid, let’s look at some procedures for getting the water out of the fluid. The process is quite similar to removing water from the engine oil.

Removing the water from the transmission fluid is crucial because doing otherwise could permanently harm the transmission.

Tools needed: 

  • Jack stand
  • Adjustable wrench
  • Empty bucket and Drain tube
  • Gloves and safety glasses


  1. Ensure that the engine is turned off and the emergency brakes are engaged.  To lift the car, use a jack stand.
  2. Identify the transmission pan. Using a wrench, remove the pan.
  3. Disconnect the drain plug and allow the transmission fluid to drain.
  4. Reinstall the drain plug. Refill the reservoir with new transmission fluid (don’t replace the transmission with engine oil). Changing transmission fluids in such cases is not an issue.
  5. Disconnect the cooler line. Cooler lines handle and transport transmission fluid. Connect one end of the tube to the line and the other end to the bucket.
  6. Turn on the engine. Water in the transmission fluid can turn pinkish. Allow the fluid to drain in the bucket until the fluid is a reddish color.
  7. Reattach the cooler-out line. Reinstall the transmission pan. The color of the transmission fluid should be reddish now, meaning water from it has been removed.

FAQ’s on Water in Transmission Fluid

The color of the transmission fluid is typically reddish brown. If water is added, the fluid's color will lighten and take on a more milky, pinkish appearance. Additionally, difficulties with gear shifting or grinding noises may indicate that your transmission fluid contains water.


In summary, having water in the transmission fluid is detrimental to the engine’s transmission system. Water in the transmission fluid can cause gearing and sludge, and lubricating issues in transmission system components.

Usually, a damaged radiator, careless driving, or a wet dipstick is to blame. Make sure to fix the problem as soon as you can. Don’t forget to drain the old fluid from the reservoir and top it off with new transmission fluid.

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