Well got back and didn't get to operate my tractor until yesterday. Anyway had a lot of brush hoging to do at some new land I purchased and operated the tractor about 4 hours. In the past it would mostly hear the clunking noise, acutually a muffled none mechanical noise hard to describe, after the engine was well warmed up and at low idle. For what ever reason the tractor did not make the noise at all yesterday. I guess I'm happy it didn't but if there is an issue I would like to deal with it while its under warranty. Otherwise the tractor has performed perfectly with no issues. More on the noise, when I've heard it in the past I kinda thought it make something to do with the turbo charger, something to do with the waste gate? I'm no mechanic but the sound was not what I would call mechanical, so actually I'm at a total loose at what is or was.