Hey bud,
really interesting you've asked this question as it's the noise i've come accustomed to for years! If it's the same noise, it is most apparent at motorway speeds and, as you say, you lift off and go into overun.
Usually after about 20 seconds or so the noise fades away.
I have also checked the hub and half-shaft bearings, not the problem.
My CV joints are probably like yours
(could really do with some new ones but it's just never going to happen due to availability and money) but also i'm not convinced that this noise can be made by the CV joints as they tend to clatter under load when worn out.
My current theory is that its the thrust bearings inside the gearbox, my reasoning being that I can make the noise go away with light application of throttle.
I'm imagining in my head that the helical gears, which will exert horizontal force as they mesh, is pushing the two shafts in opposite directions and hence is wearing the thrust bearing(s)
(if there is such a bearing in the gearbox)! So when on throttle and the shafts are under load they are, reasonably, silent.
But when off throttle and there is no load, the two gearshafts are free to move around and partially engage with the thrust bearings, meshing between the gears as they move slightly, and hence make this noise? TBH this is all speculation!! It's pretty high on my list to get another E153 box to swap in to mine while I strip down and rebuild/find all these noises, just for curiosities sake, as I have no doubt the box will last forever regardless.
Apologies for the long post, it's just quite exciting that someone else is questioning the noise!
