Heat oven to 350 degrees F. Grease and flour 10-inch tube pan. Lightly spoon flour into measuring cup; level off. In medium bowl, combine flour, coconut, rolled oats, brown sugar and pecans; mix well. With fork or pastry blender, cut in margarine until mixture is crumbly. Set aside.
In large bowl, combine bananas, sour cream and eggs; beat at low speed until smooth. Add cake mix; beat 2 minutes at high speed. Spread 1/3 of batter in greased and floured pan; sprinkle with 1/3 of coconut mixture. Repeat layers 2 more times using remaining batter and coconut mixture, ending with coconut mixture.
Bake at 350 degrees F. for 50 to 60 minutes or until toothpick inserted near center comes out clean. Cool upright in pan 15 minutes. Remove cake from pan; place on serving plate, coconut side up. Cool 1 hour or until completely cooled.
https://www.thedailymeal.com/recipes/banana-crunch-cake