I installed new clutches and separating plates in 550 pto the other day. I didn"t have a spring scale, but it seemed to snap in like it did when we got it several years ago. hooked up to 5 foot finish mower and tried it out. ran mower like it should, but would not stop turning when disengaged. a worker used it for an hour. I could smell some clutch when he stopped. the next morning, i tightened up a couple notches. after another hour of mowing, the mower stopped, but the lever was still snapping in. and when I pulled the inspection plate, some of the teeth from clutches hit the floor. was it not adjusted enough to start with? why does it freewheel when the parts are new? I used aftermarket parts from a company ive had good luck with.