I have a model 425 61X8A with a 15hp Kohler. It was made by John Deere. I have changed the drive belt but it did nothing to help the situation. My problem is that the mower only goes at a crawl. Very slow. Is there a way to change the fluid in the transmission? I can not find a drain plug. The body on this is in very good condition and was always kept in a garage. I would like to keep this going since I also have a rear bagger on this mower. It comes in handy to pick up the leaves in the fall. Any help would be graetly appreciated.