Tractor Repair: Problem with John Deere front end loader, john deere 4310, corn flake

Question
Front end loader came new on John Deere 4310 tractor.  After about 100 hours tractor operation time, the front end loader started making an occasional squealing sound that seems to come from the control valve for the front end loader.  The front end loader has no loss in power.  I changed the hydraulic fluid, and both filters.  I cleaned the screen and it had something on it resembling small corn flake cereal.  It was a soft crunchy substance.  No metal particles were found anywhere in the fluid or on the drain plug magnet.  Refilled with new Amsoil hydraulic fluid and still have the squealing valve.  Also the bucket has a delay returning or going all the way down.  Sometimes it will even go the wrong direction for a short distance.  The frond end loader is still very strong.

Answer
Sounds to me like you have a blown out cylinder. Check to make sure one side does not start moving first. The valve is only spools unless something is cracked then we have not had any trouble with them at all. What ever you found inside might be in the relief valve but if the loader is still strong then that would not be the case. Soes the sound only happen with the raise and lower action or curling the bucket also? Follow up and I might be able to help more.