Water in transmission

Water can come from the radiator or an external source. All transmissions have a cooling line that runs to the radiator. ... Sometimes, a leak develops in the radiator between the coolant passage and the transmission fluid passage, and coolant gets into the radiator.

How do I fix it?

Unless someone poured water into the transmission, the only way water can migrate into the transmission is through an eroded transmission cooler. Fluid is pumped through metal lines into the cooler, which is incorporated into the bottom of the radiator, radiator water/antifreeze leaks into the cooler and is pumped back to the transmission. To fix this, replace the radiator and flush the transmission.