Blade tilt drifting

[Littlehill]

Hi all,
Our JD grader has developed an issue with the blade tilt cylinder drifting- this makes it hard to hold in the required position while operating as it allows to blade to tip forward.
Took the valve spool apart and it seemed ok (nothing obvious stuck in there), and took the cylinder in for new seals which didn't fix the problem.
Does anyone know if there is a return to tank check valve or something similar which could be causing this? Or could it be the spring in the spool?
Cheers

 

[ovrszd]

I would blame the valve. You have already eliminated the cylinder. Not much else that could cause that.

Our right side blade lift will do that when the machine is cold. Goes away within a few minutes of operation.