In a large bowl, dissolve yeast and sugar in warm water. Stir in the brown sugar, shortening, molasses, caraway seeds and salt. Add rye flour and 1-3/4 cups all-purpose flour; beat until smooth. Stir in enough remaining all-purpose flour to form a soft dough., Turn onto a floured surface; knead until smooth and elastic, about 6-8 minutes. Place in a greased bowl, turning once to grease the top. Cover and let rise in a warm place until doubled, about 1 hour., Punch dough down; shape into three loaves. Place on greased baking sheets. Cover and let rise until doubled, about 1 hour., Bake at 350° for 20-25 minutes or until golden brown. Remove from pans to wire racks to cool.