I have a 2009 L3400, a buddy (who was helping cut my fields) engaged the pto without depressing the clutch, I also developed a not so normal noise coming from under the seat. I called my service dept mechanic and asked to send someone out to look at it, well the mechanic came and said he adjusted the pto cable and when I went back up to the property to cut, the noise was gone, I cut a good 6-8 hours stopping for breaks and stopping and starting the pto and all seems back to normal.