Preheat oven to 350 degrees F. In a mixing bowl combine flour, pecans, butter, and sugar with a pastry blender. Pat or press into a 9 x 13 metal baking pan. Bake for 13 minutes. Cool completely before covering with next layer.
In another mixing bowl, beat together cream cheese, powdered sugar, and 3 cups whipped topping. Spread evenly over crust.
Prepare pudding as directed on package, but only use 3 cups milk. Spread evening over cream cheese layer.
Spread 3 cups whipped topping on top of pudding layer. Chill for 2 hours, cut, and serve. Refrigerate any leftovers.