A sealing and drainage device for a motor vehicle transmission is located in a wall approximately near the bottom of the transmission housing and includes a ball and a plate that encloses the ball in a bore through the housing wall. The plate has an opening on which the ball sits under normal operating conditions. During unexpected flooding conditions, water flows through the opening into the bore. The ball floats on the water such that as the water rises in the bore, the ball rises as well to the top of the bore to seal the bore from the interior of the housing, preventing water from flowing into the housing.