Grease and flour two 5 x 9 inch loaf pans. Cream sugar and mayonnaise, add eggs, mix thoroughly. Add mashed peaches, mix well. Add flour, cinnamon, baking powder and soda, mix well. Add vanilla and chopped nuts, stir until well blended. pour into two well greased and floured 5 x 9 pans. Bake in a 325 degree oven for 1 hour. Cool bread in pan 5 minutes before removing from pan.