TO 20 Rock shafts

I am attaching a rotary mower to my TO 20. If I set the mower at the right height, before I know it the mower drops. Setting is not constant. So I was just going to drop the rock arms all the way down, and install a adjusting yoke on each side and raise the mower to the desired height and is should stay. Problem is the adjusting box hits the axle housing. I want to know if the rock arms are adjustable. If I could just raise the low point of the rock arms, the adjusting box will not hit. Any thoughts? Stan

your mower has to have a solid top A frame that is were the top link goes from the mower to the tractor and that top link has to push the big spring under the set in to make the three point hitch maintain a constant height. to-20 have pressure control NOT draft . you DO NOT need any chains or other junk to make your mower stay at the set height any questions call me 9208517182 and i will tell you how to set it up and you will need nothing more then you tractor and mower. trust me i have helped meany with this

If I understand correctly, I think I can address your problem. I have a TO30 I use with a rotary mower. I have used two different means of maintaining mower height.

1. As described by marlow, if the everything is rigid put the mower on a level surface. (I usually disconnect PTO shaft so I can run hydraulics without spinning blade.) Lift mower slightly, move quadrant lever to stop it from rising. It will slowly settle. Now turn top link to make it longer and apply pressure to large spring. If your draft control mechanism is working, as the spring comes under pressure the lift arms will start to creep upward. Once you find the right place they will hold constant height indefinitely. This works like a charm on level ground. The only problem I ever have is a sudden change in grade that changes the compression on the top link and thus causes the mower to lift or fall quickly. Perhaps a wiser soul can resolve that issue. You can read about this in the archives written better than this.

2. Also in the archives are (vague) descriptions of various position control mechanisms that people have made and added to their Fergies or 9Ns. I have tried two iterations. My current one is made of wood and CPVC. This works great for mowing, too, and has the added benefit of also working for using a carryall, etc. It is essentially a feedback mechanism that pulls the quadrant lever up as the lift arms fall or pushes it down as they rise so that it self regulates.

Both items above require hydraulics that work as they should on a TO20/30. If the hydraulics are inherently broken, that's a different issue.