Water in tranny

[agng]

Does anyone know how water or antifreeze can get inside tranny ?
It's all started from whine in transmission, and about 2-3 seconds delay to engage reverse. When I drained the fluid, it looked like someone have mixed some milk with it. I did put new filter and also drained fluid from torque converter, put fresh stuff inside and went for a test drive. It does shift fine, besides little delay into reverse, which I did not have before this.
I have removed two tranny lines from radiator, put my finger into lower one, and pumped some air into top one with bicycle pump. I was hoping to see bubbles in my overflow tank, but nothing in there. I'm assuming my tranny cooler is OK. I also did check for a breather on the back of a tranny, and it is there. I'm not loosing any water from the tank either.
Is there any other ways for water or antifreeze to get inside of it ??

1990 300E 722.358