Yea, Im guessing the o-rings and crush washers just seal all the external passages and is gonna do nothing to how the valve operates internally. And if you have never had a valve apart, you will see that.
Most quality loader valves will have anti-drop load checks that prevent exactly what you are seeing when trying to feather the valve.
Simple valves like logsplitter or hydraulic presses dont have load checks, because there is no backpressure.
Meaning that there is a fair bit of pressure just required to hold an empty loader suspended. Most loaders this would be around 500-600psi when empty. If you were to tee a gauge on the base of the loader cylinder....even emptym the weight of the loader imparts that pressure on the oil. Even more so when loaded.
So what happens is your system pressure is at 0....being its an open center system and simply pumping oil thru the valves and back to tank....and the only pressure is the resistance of the passages and fittings. (so not exactly 0, but for all intents and purposes.....no pressure on the system.)
Now when you try and move the valve very slowly.....the pressurized oil has TWO paths to take....out to the loader cylinders, or back to tank. Because when you only "slightly" move the joystick in attempt to feather a load, you are starting to close off the "open center" passage back to tank, but not completely.
So the 500-600psi in the loader cylinders just because of the weight, overpowers the pump trying to fill and raise the cylinder....and backfeeds into the pressure side of the spool, which is still partially open to tank.
I hope that explanation makes sense to you. But this is where load checks or anti-drop valves come into play. Sometimes they are servicable and parts are available, sometimes not. Or some cheap valves simply dont have them. If yours has them, there could be a little piece of debris caught in one (like a shard of teflon tape) and a thorough cleaning may fix the issue.
But gotta ask, is this a new issue? OR always been like this? Because if its always been that way, you may not have load checks at all. And sadly, the only way to keep a load from dropping when trying to raise is to shift the lever FAR enough to close off the open-center passage from the valve inlet. Which may be faster than you desire when trying to feather a heavy load.
Sorry to be the bearer of bad news, but the o-ring kit aint gonna fix it. BUT, while its apart, disassemble everything you possibly can and clean real good, and if contamination of some kind was causing the issue, it may just fix your problem
