I got an older B7100D tractor not too long ago. When I lifted the 3 point then put the control valve in the neutral position, it would fade down to the ground. Tore it all apart and discovered the o-ring on the piston was the wrong size (too small) so I replaced it with a bigger one and put it all back together. Well, now the 3 point will lift when I pull back on the lever if the revs are high enough on the engine but if idling will drop when I pull back (same direction). The good news is that it holds up in the neutral position now so I've got that going for me. What would cause it to both lift and drop with the lever in the same position, depending on rpms? I pulled it back apart and don't see anything obvious but it's my first time working on a tractor like this so who knows? Maybe it just needs a good bleed? Thanks!