Place your roast in the slow cooker. Combine the gravy, mushroom soup, brown sugar, vinegar, soy sauce, Worcestershire sauce, and dry onion soup mix. Stir until smooth. Pour the mixture over the roast in the slow cooker. Place the lid on the slow cooker and cook it on LOW for 12 hours or cook on HIGH for 7 hours. This will be the most tender roast you have ever had. Enjoy.