wd hydraulic valve adjustment

Put my pulling WD to work today. I bought a new place and needed to brushhog 3 acres. how do i adjust the valves so that i can set the lift hight and leave it be? it keeps creeping up or down. pain in the butt to have to watch it every second and look ahead  because i dident know what was buryed under the grass. I did find a spair tire and wheel from a honda, snaped the sheer bolt on the cutter and the bolt on the coupler and the PTO gear box. So who knows about this valve? Thanks Andrew

Here you go.

My WD does the same thing with a bush hog. I have tried to adjust the thing like the book says, but I think it needs the hydraulic pump rebuilt with new seals...it won't stay no matter what I do. One guy told me on this forum that it was not made to sit in a stay position from the factory...I don't know if that is true or not?   I have installed a needle valve in the hydraulic line. I can set it down to where I want it to be then shut the needle valve, and it will stay there. BUT if you want to lower or raise the bush hog I have to open the needle valve. Since I have a loader and the three point on my WD, I actually have two needle vavles, one in the line that goes to the loader cylinders and one that goes to the back 3 pt cylinders. That way if I have a blade on the back and I want to set it in the raised position, I can raise it up and shut the needle valve on the back and it will stay up and I can still run my loader up and down as I wish. It works the other way to, I can set my loader in an up position, shut the needle valve in that line and use the back 3pt with blade.
The other thing like Chuck said was go to a farm store and get the spacer set that goes on the rod of the hydralic cylinders to set them up so they won't go all the way in.
Hope that helps a little.
Pastor Mike