Re: CV joint gone?
Does it sometimes make the noise more often when you lift off from the accelerator?
Does the noise sound "in time", or consistant with, the wheespeed/revs.
i.e. the frequency of knocks changes pretty much linearly with speed when it occurs.
If so it could well be a CV-joint.
If it doesn't happen with the clutch in - then its less likely, but is still possible with (very) chattering splines.
CV-Joints aren't hugely expensive, the labour would be more - you can just buy the part you need once it is diagnosed.