winterize...transmission question

I was trying to drain all the water out of my engine. I have a 310 Predator engine in my 02 X-star. I drained the block through the drains on both side, and disconnected the quick connect of the manifold hoses. What about the transmission? There is an in and out line going to the top of my transmission from the main raw water intake. I'm assuming this is how the transmission gets water cooled? Is there a drain on the transmission somewhere to get the water out? Is there water trapped in my transmission that I have to worry about freezing up? Last year I ran antifreeze through my engine. I wasn't going to do it this year because neither of the local marinas run antifreeze through the engines here in Wisconsin. They both say it isn't necessary. It seems like the forums aren't in agreement either.