Water In Transmission
If your vehicle has a dipstick (some don't), diagnosing water in the transmission is easy. Look at the fluid. It should be bright and cherry red. Even if it's burnt brown, you should be able to see through it. If it's milky (looks like a strawberry milkshake), you've got water in the transmission.
Figuring out where the water came from is a different story. To do this correctly requires a Free Diagnostic. 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. On other cars, rainwater leaks into the fluid, usually through the dipstick tube. Some cars have actually been recalled for a poorly positioned dipstick tube which allowed water to seep into the transmission. It doesn't take much--less than an ounce of water can cause problems.
Sadly, once water gets into the transmission enough to affect operation, a rebuild is required. The clutch facings in the transmission absorb water, and there is no way to get it back out. They won't engage properly any more. No amount of flushing or fluid change will cure this, and there is no additive that can help. Fortunately, if you address this quickly, the hard part damage will be minimal, and you'll save a lot of money.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .