Jerky boom on a Case 580CK

Have had a problem with the boom motion of a 1966 Case 580CK backhoe for the last 16 years. When the boom control lever is moved, just a little, the boom moves uncannily fast, and the engine sounds a bit strained when at a slow idle. This happens in both directions - up and down. The difference in control lever position for slow raise and fast raise is almost imperceptible. Move the lever just a little, and the boom barely moves. Move the lever just a little more, and it is at full speed. I have used other 580's (although newer), and they are much more controlled than this one. All the other backhoe and loader functions are nice and smooth. RPM is about 1500. I verified that the flow restrictor (p/n D27565) is in the boom drop line, and that it is installed in the proper direction.

I have purchased the 4" thick shop manual, parts manual, and loader manual for guidance, and the only reference to this type of problem is the flow restrictor. Ben Winkler was the local guru in this area, but about a decade ago, he was crushed by a combine wheel. It took until now to think about using the web to help solve the problem.

Thank you for any ideas!
Greg

You COULD try a swap to see. Unhook the boom cylinder (you mean shoulder one?) And hook those lines to another cylinder like wrist etc and see if it acts same after. Thats the easy cheap way to test. If it does its the spool valve needs rebuilt. Usually they dont need replaced just rebuilt with seals and cleaned. Even a dirt particle can cause that as the tolerence in the valve is very small.

I am not sure what you mean by the shoulder one, but it is the cylinder that makes the boom go up and down. The dipper and bucket cylinders act nice and smoothly.

Yes. The boom is jerky both ways - not just downward. Would I remove the spool valve from the underside of the valve body? There is not much room in there, and I am not that flexible, so would like to take it apart the first time if possible.

Thank you,
Greg

My 2¢

Joe Ferguson

I will bleed the system. Thank you for the suggestion.

Greg