PTO starts clankin when I use my roto tiller in firm ground (no stones) if I try to go to deep. Its like the cogs don't stay against each other and get out of time. By that I mean they are under load (quiet normal operation) and then they sound like they are hitting back and forth as if the tiller jumps ahead and the cog on the tiller side hits the drive cog and then the drive cog hits the tiller cog (the clanking) until you lift the tiller out. I am goin very slow but once they get outa time I need to raise the tiller and then I'm back to normal. It has only happened in this one soil condition. Things are properly adjusted before you ask. It just may be a normal with this type of cog/pto set up or with this roto tiller combo. Just wondering if anyone else has experienced this.. Thx for your replies.