Need Help!- Whistling and grunting

[Rodtp]

On my Syil X5+ when in cnc mode, connected to Mach3 but no prog running, x axis motor whistles quietly. When shift+ left or right arrow to make table move rapidly, it will occasionally grunt and stop moving whilst grunting. In diagnostics, checking movement by asking for a say, 4mm move it sometimes grunts and moves 1 or 2 mm. Computer driver reports excellent. The vertical movement has a much more smooth sound if it is run up to limit and then run down. If stopped and restarted it resumes it's rather grungey sound. Any ideas gratefully received.

[neilw20]

Remove power, and temporarily swap X and Y motor cables.
Power up, and if the Y axis starts doing it (with X commands from Mach3) , the driver is faulty or current limit not working correctly.
If the X axis movement (being controlled by Y axis on Mach3 still exhibits the same problem, then the stepper motor is faulty.
It is possible stickiness int the X axis could cause it, but that is a remote possibility.

By substituting X and Y, wires, cables, PC ribbons, etc, most faults can be isolated to motor/driver/cable PC problems.

Ensure all connectors, crimps, etc are OK. Tug each wire firmly. Loose terminals/crimps/pins can cause all sorts of strange problems.

Particularly motor connectors, which can upset the current mode operation of the microstepping drivers.

[ramax]

1. Is the machine latest series?
2.Has it just started doing this or like this from new?

[Rodtp]

Many thanks for the suggestions. It transpired the X axis is a litle stiff (new machine). I changed the computer for a later one and have reduced the acceleration and speed a smidge and this appears to have cured it.