3400 hydraulic issues

[STEVE BARRETT]

i have a 1966 model 3400 ford tractor which has hydraulic issues after a topcover overhaul. when in position control all of the movement is either at the top of the position or bottom of position.as soon as you move the handle it goes either all the way up or all the way down,nothing in between.i have had the cover off several times and the setttings are correct according to the fo31 service manual,makes it very hard to operate a bushhog, what am i missing? thanks for looking, Steve in ga.