Ok, the this model did tend to have some hydraulic noise. Some things to check. Condition and type of hydraulic fluid will have quite an affect on hydraulic system noise. I recomend kubota Super UDT for this application. The fluid is recomended to be changed at least once a year, I know that with this few of hours it is unlikely that it has been changed, but keep in mind that condensation and to a smaller part evaporation will cause physical changes in the fluid. The first course of action is to replace the hydraulic fluid and filters. I would suspect that one of the remote valves may be sticking slightly and causing the system noise. The good news is a hydraulic pump on these is relatively inexpensive to replace if it does fail.
The valves are supposed to lock into float possition, however sticking in the other positions is almost always caused by corrosion in the detent housings, sometimes they can be removed and lubed and be made to work satisfactory. However often times they need to be replaced, I would suggest coating them well with a corrosion inhibiter such as Fluid Film, before installing the new detents.
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Well, yes in fact without pressure and flow testing all you are doing is general speculation. It is beyond the scope of most do it yourselfers and, for that matter a lot of repair shops to perform this testing. In this particular case, extensive testing can often be much more expensive than replacing components. I hate that REAL diagnosis can be so complicated. Specifically, the pump will need to be flow rated at each section of the system. Directly at the pump, and then at after each component in the system to pinpoint where the problem may lie. The most frustrating thing is that there may not actually even be a problem. Is your hydraulic fluid abnormally hot? If you are not heating up the fluid the likelihood is that there is actually no problem at all. You can try feeling the hydraulic pressure line as it goes through each component and see if anywhere along its path it seems to get significantly warmer. If it does, there is likely a restriction in that component.
Hope this addition info helps.