Tractor Repair: JD F910 hydraulic steering problem, piston seals, garden tractors

Question
Arnie, I know that you do not handle garden tractors but I was referred to this area from another ask area.  It is a commercial unit so maybe its still in your area of expertise.
I need help on diagnosis of a JD F910 hydraulic steering problem. The steering suddenly now is very sloppy. When going from one direction to the opposite it takes at least a half turn on the steering wheel to make any change. Also, it under steers to the right and over steers to the left past the usual stop point. Tie rod and ball joint looks tight (and I replaced the ball joint a short while back).  I do think its hydraulic related but the steering has several systems involved and don't know where to begin. Any help would be appreciated.  Thanks.


Answer
Hello,

  Just taking a guess since I'm not familiar with what type of power steering system they have.  Oil bypassing inside the cylinder possibly due to bad piston seals inside, or a bad steering control valve.  Again, these are just a wild guess since this is outside of my area.  

                          Good luck,

                              Arnie