Tractor Repair: 3588 2+2 steering, truck mechanic, drive shaft

Question
our 3588 steering went hard in both directions while working in the field, can turn if moving and extreme force applied to wheel, have cleaned and checked flow valves and directional valves, truck mechanic by trade, feels like equal pressure on both sides can you maybe give some guidance as to pressures at left and right rotary motor and if there is a common factor brakes work ok any help would be appreciated thankyou

Answer
  Does the pto and any of the other hydraulic systems such as hitch and remotes work?  If not, then the drive shaft that drives the pumps and pto is not turning.  The splines wear and strip out where the shaft goes into the pressure plate of the clutch.  If the problem is only with the steering, it gets its oil from a separate pump under the transmission.  If you can turn the machine by applying extreme force on the steering wheel, then the control unit, steering cylinders, and alternating check valve should be OK so check the steering pump.