404 steering problems

[mic560]

I have a 404 and am having some problems with the steering. I bought the tractor in the condition it is in and it doesnt have the original steering on it. I was told what is on it was the same is what is on the 504 but I honestly dont know. What it has is hydrostat steering that has a 2 line steering motor and what I would call a diverter valve. Now I guess the real question is does that type steering need constant preesure or can it be used with an open center system? My nest problem is that the hydraulic line that feeds the steering off the priority valve doesnt have a good flow at all it is pulsing. What would cause that I have taken the priority valve apart everything apeared to be in good shape it all looked liked new and fit well together. Is there a certain amount of tension that springs needs to haveto make it put a good stream of oil to the steering? The 3 point works really well and fast. The releif is squealing at 1450 psi.I am kinda thinking that maybe that spring is colapsing way to easy and just letting the oil go to the three point but the steering doesnt work even when the 3 point is all the way up and making the releif squeal