Water in Your Car’s Transmission

Water in the transmission spells trouble, even a very small amount can create massive problems. But how does it get in there in the first place, and how can you prevent it from  getting inside?

If your transmission fluid looks like a strawberry milkshake, you’ve got water in the transmission. Once water gets into the transmission enough to affect operation, a rebuild is required. It doesn’t take much–less than an ounce of water can cause problems. Fortunately, if you address the issue quickly, the hard part damage will be minimal, and you’ll save a lot of money. Here we will cover why water is bad for the transmission, how it can enter get into the transmission and how you can get it out quickly in order to avoid a rebuild.

Why is water in the transmission bad?

When water gets inside of an automatic transmission, the friction lining of the clutches absorbs it and dissolves the glue that attaches the material to the clutch plates.  Usually, some amount of water will come out of suspension and form white gummy masses in various areas of the unit. This is why the unit cannot be flushed to remove all of the water. In addition, the presence of water will start rust forming on the ferrous metal parts throughout the unit.  The amount of water and the length of time that it is inside of the unit will determine the extent of the damage, but the resolve to the problem will be to overhaul the transmission.

How does water get into the transmission?

There are plenty of ways for water to find its way into the transmission. Figuring out where the water came from is tricky. Water can come from the radiator or an external source. All transmissions have a cooling line that runs to the radiator. A separate fluid passage circulates the transmission fluid through a portion of the radiator to cool the fluid. Sometimes, a leak develops in the radiator between the coolant passage and the transmission fluid passage, and coolant gets into the radiator.

One good pass through a deep puddle can soak the unit’s insides. Or if the car stalls in a flash flood rainstorm at a low spot in the road.

All transmissions have a vent to maintain equal barometric pressure inside of the transmission.  If the vehicle is driven through water (as in a flood) and the water level is at or above the vent, the water will cool the unit lowering the internal temperature and water is drawn inside of the transmission.

On other cars, rainwater leaks into the fluid, usually through the dipstick tube. Moisture can effortlessly enter the transmission if the dipstick was sprayed during an engine cleaning, or in some situations, water draining from rain or a carwash drips onto the dipstick. Some cars have actually been recalled for a poorly positioned dipstick tube which allowed water to seep into the transmission.

How can I get the water out?

We recommend you visit your nearest Mister Transmission for a free diagnostic. They can determine how the water got in there in order to avoid a reoccurrence and do a fast, thorough flush with new transmission fluid. In some cases, this process will require several dozen quarts of fluid. There is no shortcut that will repair the situation. Several factors including how long the automobile was driven with the contaminated ATF, the kind of gearbox your automobile has and how much water in total got in can all affect the outcome, in other words whether you need a rebuild or a replacement.

Water inside of an automatic transmission is highly destructive and there are few things more damaging to a car than water in the transmission fluid. If left unaddressed, the friction plates in the transmission will separate and the transmission will no longer shift into any gears. This will almost immediately begin corroding the iron in the transmission. Because the transmission is made up of very delicate parts, it can very quickly be destroyed so be sure to get the car towed to your nearest Mister Transmission!

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