I have a Crafesman zero turn mower with over 1700 hrs. It runs really well but started lurching at low speed. The oil was low in both transmissions. I added oil and thought it was fixed but it started lurching again but not as bad. Trans suppose to be maintenance free but after 1700 hrs on an air cooled engine (Kohler) things go bad. Anyone have any thoughts? It does fine at high speed. Its almost like an engine hunting. The engine runs very good at low and high speed. I know the engine has to run well for the trans to work like it should. Thanks for any help. I should have put this on the Craftsman forum. Getting old.