Hi, yesterday I noticed that I had a knocking noise and there was a little grinding sort of noise with it. I tried disengaging the PTO and the noise stayed. While I was turning and I pressed the brake pedal to help turn sharper the noise got worse. But I noticed that whenever I pressed the clutch in the noise left. Everything was purring like always. Then right before I put the tractor up the noise went away all together. Well this morning I was going to plant a few rows of purple hull peas and I got the tractor out and the knock was there not as bad but present. And it didn't matter if the clutch was in or out the knock was still there. The knock got a little worse before I put it away but not too bad. My oil pressure doesn't drop, I'm not smoking. And I'm lost since it seems to change when the knock starts and it will stop at times. The motor was rebuilt a few years ago. If anyone could give me any ideas as to where to start looking I would appreciate it.