Tata hitachi ex110 swing problem

Hi guys, Iam having tata hitachi ex110 in this swing does not stop suddenly on left side when i swing on right side it stopping but not suddenly.and produce some some sound in swing area.and in my swing motor there is a oil leakage from one bolt which it is a allen key bolt. i think it is a adjusting bolt.and i have grease leak with oil in under the cabin Please suggest some ideas.and my machine runs only 8700 hrs..