I have recently looked at the JD4520 and like everything about it....almost. When test driving it the salesman had to idle the engine down to a very low RPM for us to carry on a conversation. The diesel compression knock seems to be almost as loud as on my old IH424. I then test drove a kubota 5030 and found it to be much quieter. I would picture myself needing hearing protection when operating the JD but not the Kubota. I would appreciate any comments on this from current owners.