Heat oven to 350°F (325°F for dark or nonstick pans). Grease bottoms and sides of four 8-inch round cake pans with shortening.
In large bowl, beat cake mix, milk, melted butter, eggs, cinnamon and nutmeg with electric mixer on medium speed 2 minutes. Stir in carrots and pecans. Spoon and spread batter evenly in pans (about 1 1/4 cups batter each).
Bake 18 to 22 minutes or until toothpick inserted in the center comes out clean. Cool 10 minutes; remove from pans to cooling rack; cool completely, about 1 hour.
In large bowl, beat cream cheese and softened butter with electric mixer on medium-high speed until smooth. Beat in caramel sauce and the vanilla until smooth and creamy.
Frost cake using 2/3 cup between layers. Frost sides with a thin layer of frosting so sides are covered but still showing through. Spread remaining frosting on top. Refrigerate uncovered at least 2 hours.
When ready to serve, drizzle caramel sauce over top of cake. Cover and refrigerate any remaining cake.