Preheat oven to 350 degrees. Mix together cake mix, eggs, oil, and mandarin oranges and juice; pour into a 9 x 13 inch greased and floured pan. Bake for 30 minutes or until done. Pour 3/4 cup juice from crushed pineapple over cake while still warm. Mix pineapple with pudding powder and Cool Whip. Spread over the cooled cake.