Have to agree with Mklotz. I replaced my z-axis strut and went with two on the side. The Z would whine holding the load at times. Perhaps on your axis, it is more of an alignment of ballscrew, nut, end-flange etc. putting some pressure on the shaft? Perhaps even loosening the Servo screws may help. Outside of that, have not needed to do much tuning on the Drives, at least from the last number of years. If I find something, I'll post something up.