I just saw this thread. if you have flow diverted to diffy it means two things. it is either diverted from pressure relief device to diffy and in that case the valve should chatter against seat and spring. You will for sure hear that. Secondly, if the spool valve is in neutral position at any height the flow is diveterd to diffy thru spool valve.
Are you sure if your pump inlet is flooded, pump not cavitating and actually pumping? if you take the relif pressure cap off and a bucket to collect oil then you can verify pump flow to relief device.
On the lift cylinder head if you take the nut off on the left hand (from driver sea) then you can verify flow to the cylinder head.
with the rate of drop knob fully closed (turtle position to the max) then you can raise the 3 point but once reaches max it can no longer accept fluid and all have to by pass thru spool valve on neutral position.
My wild guess is that your are not pumping oil. what do you mean when you say flow is diverting to diffy, are you running the tractor with lift cylinder head removed and then you observed flow?
JC,