my dealer opened the drain plug and left it open
a couple years ago, I got water in it in a waterhole, not discovered till ccold weather set in, all of a sudden my 450i wouldn't move at all. turned out, my belt was just frozen in a block of ice, when I saw how much work it is just to get to the belt I had my dealer come get it. they let it thaw and pulled the plug, good to go, been that way for nearly 3 years, I have lost about 1 mph in top speed over that time, nobody will make me believe that it not normal belt wear for the amount of log skidding and towing that I do.