Looking for help in diagnoses before I tear into this thing. Have a FarmPro 2425 with Y385 engine. Most recently been grading and land clearing. Have a couple of small hydraulic leaks, so before the long day began, I topped off the rear Hyd for the drag box operation. Just a few minutes into working, I backed into a stump and bent dragbox braces and stopped the engine while I attemped to straighten braces. Needed tools, so I headed back to the garage with the tractor. About 100 yds later, the engine started a load knocking. I shut it down immediately. checked oil and found it to be about 2qts high...over filled. Drained the oil and put in new oil to proper levels. Started just fine, but the loud knocking continues. Never got any indication of overheating, had good oil pressure. Engine only has about 40 hours on it. I used to rebuild VW engines as a young man, kind of sounds like I dropped a valve? I have absolutely NO experience with diesels. Anyone want to give me a starting point? Pull the valve cover? Or could this be some sort of a fuel issue causing the knocking?...like a misfire? Oh, tractor is out of warranty, bought in April of 2003. Suggestions/comments very welcome and much appreciated. OLY