Tractor Repair: IH 806 hydrailics followup, broken spring, cold climate

Question
My brother posted a question earlier about our dad's 806 http://en.allexperts.com/q/Tractor-Repair-838/2011/1/IH-806-Hydraulic-fluid.htm Thanks for the information. I have a little more detail now and was wondering if that would help narrow it down.

The manual says something about manual steering when the power isn't working. I don't notice any manual control, if I force it it feels like the steering wheel is racheting around. If you raise the front axle by lowering the front end loader the steering returns and I can move the wheels either direction fine.

With the tractor in gear and moving I can bareley move the wheels to one side but not the other.

Does any of this info help narrow down the problem?

Thanks,

Answer
 No, it doesn't help much.  With the extra weight of a loader on it or if you are in a cold climate, you probably won't be able to manually steer it anyway even if the manual steering is working.  At least if you force it, the wheel ratchets and doesn't just spin easily without forcing it.  That tells me the manual steering is probably trying to work.  If the sump check valve is bad, the oil drains out of the steering system and the wheel just spins easily.  The steering, brakes, and TA get oil from the same pump.  If the brakes and TA work OK, then the steering relief valve could be stuck, have a broken spring, or a blown o-ring.  If the brakes and TA are weak also, then the pump is worn out.  It's hard to accurately diagnose sometimes without hooking up gauges and doing some pressure testing.