Purchased a John Deere 140H3 last week from a farmer. It ran great for two days. Went out today to show it to my brother today and it wouldn't move in forward or reverse. Tightened the free-wheeling knob all the way down and still nothing. Loosened the knob about half way and the machine would lurch forward then stop, lurch forward then stop... Nothing in reverse. also, I cannot find an operator's manual on the internet. The decals describing which control does what are missing. Can someone provide a link or source for a manual, or at least describe which control does what? Particularly, the threaded shaft on the left, just below the console, and the round knob control just below the throttle. Thanks.