Place roast in a very large plastic, glass, or stainless steel container. Combine wine, onion, celery, carrots, peppercorns, bay leaves, cloves, and salt; mix well, and pour over roast. Cover and refrigerate 5 days, turning roast each day.
Remove roast from marinade; pat dry. Strain marinade, reserving marinade liquid; set aside. Discard vegetables and spices.
Melt 2 tablespoons shortening in a large Dutch oven; brown roast on all sides. Add reserved marinade liquid. Bring to a boil. Reduce heat; cover and simmer over low heat 2 hours or until roast is tender. Remove roast to a warm serving platter, reserving pan liquid in Dutch oven.
Melt remaining 1/4 cup shortening in a large skillet; add flour and sugar. Cook, stirring constantly, until flour is browned. Gradually add 1 1/2 cups reserved pan liquid, stirring with a wire whisk. Cook over medium heat, stirring constantly, until gravy is thickened and bubbly.
Combine gravy with remaining pan liquid in Dutch oven, mixing well. Add gingersnap crumbs; cook, stirring constantly, until smooth and thickened. Spoon gravy over roast.