I have a Gravely Promaster 44Z. I have had it for 4 years and have no problems other than when I try to mow parallel on a slight incline the rear tires want to slide down hill. My wife uses a John Deere GT 245 mower and has no problem on very steep hills that I wouldn't even attempt. I have seen others with ZTR mowers mowing parallel on very steep slopes and having no problems at all. I don't want to get rid of the mower but it is very dangerous if your not paying attention to where you are mowing.