Interested with anyone's answer. I too have had the same issue. Though I haven't had the pto running in a while, and the tractor been only ran occasionally this past year/summer. I heard what sounded like a marble, rattling in the rear end . The only time it would stop, was when the clutch was pushed in if I remember right. I also thought that the lever arm linkage was out of adjustment, but the lever arm that goes into the rear end has so little movement between when the pto is engaged or not engaged that I couldn't really adjust it . if I did, then the pto would not come out of rotating, and if I moved the nut a thread or so in the other direction it wouldn't engage at all. The hand lever is up by my right hip, and has a out 4" movement from on to off, but the actual lever arm that comes out of the rear end moves less then 1/4". And even a 1/16" of an inch I found made a difference to being engaged or not. If I don't have that hand lever right up until it brings up in the slot/fender, It may grind. Anyway, Sorry I can't be of help, But Im interested in hearing any responses you may get.