Patrick

   I ended up swapping out the entire hydraulic unit from my parts tractor except I used the same hydraulic pump and external hydro valve. The other hydro unit also had the expanded fluid reservoir. The problem lied in the internal hydro valve being worn out. There is allot of small items that can cause the fade and in my case it had nothing to do with the fluid or filter. The filter is on the return side of the hydraulics so that wouldn't cause any fade issues but if the filter is dirty or you have dirt in the fluid that will ruin your pump which will cause fade. Unless your fluid is old I wouldn't change it yet as I'm sure you'll end up pulling the hydraulic unit off and changing it at that point anyway. 

  Does the tractor fade when cold or hot? When it fades does it recovery to it's height quickly? When you see the implement rising back to it's position do you hear the hydro pump winning at all? When you turn the tractor off and have the 3pt raised up does it stay raised or does it bleed down quickly?

Thanks
Eric