Tractor Repair: valve squeel when pto is working, squeel, control valve

Question
I have a IH 584 tractor with 2900 hours. When the pto is engaged, and up to speed, i have squeal that comes and goes. I have changed the filter and fluids regular. I can feel vibration in the steering and pto lever. When i release the pto the squeal stops immediately. If i reengage the pto the squeal does not start right back. where do i start?
Fred

Answer
Hello,

  There are numerous valves and spools in the multiple control valve in front of the left rear axle.  These spools control regulated pressure, steering pressure, pto pressure, lube pressure,etc.  There could be a spool sticking, or a gasket or o-ring that is partially blown in the multiple control valve.