Unknown vibration and noise.

[StackAttack]

My car is a 2004 3.0R SpecB.
So there's been a noise progressively developing somewhere on my car. Tyres needed replacing and thought it could have been those but turns out it wasn't. Then I thought it was a wheel bearing so I put the car on a hoist and checked all four corners for play, rear left had play so I booked it in for a new wheel bearing/hub. I go to pick the car up this afternoon and the mechanic tells me that the noise is still there but that the wheel bearing was definitely making noise. So that's one problem fixed but the original noise is still hanging around. The mechanic reckons it's coming from the centre diff, though I'm not sure how he came to this conclusion.
The noise doesn't change with engine RPM but is influenced by road speed. Driving at 110KM/h and putting the clutch in means the noise slowly decreases as speed comes down. As far as I can tell it isn't affected by the car being cold or up to temp.

Around the same time this noise developed, a vibration that only occurs around 40KM/h also made itself known. This vibration isn't affected by selected gear or by the car being cold or up to temp either.

So my question is, do the centre diffs tend to make a quick, sort of 'pulsing'-like noise and cause vibration when on their way out? Has anyone else experienced a similar noise or vibration in their Spec B's?

[Curley5959]

Could be something like a buckled wheel or bad wheel balance. Do you have any trouble with turning the wheel at low speeds (such as carparks) with clunking? That would indicate a problem with the Centre Diff. Have you tried rotating your wheels? Does it affect the noise/vibration in any way? It is also possible it could be a CV Joint. Any clicking or grease leaking from the boots?

The vibration around 40km/h could be related or could be something like a buckled rotor? Any trouble with braking?

EDIT:

Is it possible your Drive Shafts are not OEM and are aftermarket. Some cheaper ones can cause vibration:
viewtopic.php?f=6&t=22858&p=328390&hilit=aftermarket+drive+shaft#p328390

[StackAttack]

I do know that one of the wheels is buckled, though it has been that way long before these symptoms showed up. Tested the carpark clunking today and there is none. Swapped the front and rear tyres around, the noise didn't move around the car at all, so I know it's nothing related to the wheels specifically. Put the car on my hoist and there was no weeping grease from the CV boots. Turned the front two wheels while the car was in the air and heard a metal on metal squeak coming from the front right wheel that didn't exist on the front left corner. I'm still unsure if it's the shaft or the bearing/hub though. Is there any way to tell just from looking at the drive shaft if it's OEM or aftermarket? I had a look but couldn't see any markings or stickers on them.