For the cake: Combine the vegetable oil, sugar, and beaten eggs in a large mixing bowl; beat at medium speed of an electric mixer until well blended. Stir in vanilla.
Combine the flours, baking powder, baking soda, and allspice in a medium bowl; stir well.
Add the flour mixture to the sugar mixture alternately with the chopped pear, beating at medium speed until blended. Stir in the chopped pecans.
Pour the batter into a greased and floured 12-cup Bundt pan. Bake at 375 degrees for 55 minutes or until a wooden pick inserted in center comes out clean. Let it cool in the pan for 10 minutes; remove from the pan and let cool completely on a wire rack.
For the drizzle: Melt the butter in a small saucepan; add the brown sugar, and cook over medium heat, stirring constantly until the sugar melts. Remove from the heat.
Add the milk to the butter/sugar mix, stirring constantly. Add the powdered sugar, vanilla, and salt. ABeat at medium speed of an electric mixer until smooth. Drizzle over the cake when it is cool.