Well this is my first o ring replace on the Kontac valve stack without taking fully out and apart. I just want to stop the oil leaking out of control valves. I started to drop out the spool from underneath valves (bottom)and it is not sliding down and out. Is binding about an inch or so after dropping. I am wondering if I should take apart centering spring which is at the bottom of spool and then travel the spool up instead and maybe not have this problem ? This is an 1988 machine. It is an LB620 New Holland. I need some expertise in this repair and hoping some one will give some experience and guidance. Also I can not even get all the parts from MFG. "O" rings they have,,, I especially need the top valve pack seal (harder plastic surroundment.) to keep out the dirt. Any and all help or where to go will be appreciated.