Preheat oven to 325 degrees.
Grease and flour 10 inch bundt or tube cake pan.
Combine cake mix, eggs, bananas, oil, sugar, milk, and vanilla extract in large bowl. Beat at low speed until moistened, then beat at medium speed for 2 minutes. Stir in pecans. Pour into pan. Bake for 50 - 60 minutes or until toothpick comes out clean. Cool in pan for 25 minutes; invert onto cooling rack and cool completely.