What would make a noise like this?

[FlatPack]

My Legacy GTB has started making a loud whining noise when braking (or just lifting off the throttle for that matter). The noise goes away if I dip the clutch and it's pitch is related to engine speed, not road speed. It seems to be related to how hard the car has been driven - if I push it hard as soon as it's nicely warmed up, it'll start making the noise straight after that. If I just pootle across town on my commute to work in stop start traffic (which takes longer), it stays quiet.

Any ideas what it could be? Someone suggested clutch release bearing, but wouldn't that make noise when the clutch is pressed and be quiet when it's released?

Oh it happens in any gear (well 2nd, 3rd and 4th anyway, not tried 5th or 1st). I guess I should see if it happens in neutral too.

[BB-Q]

There's a basic rule of thumb to use:

If the noise appears when your foot's on the clutch then it's the clutch at fault.

If the noise goes away with your foot on the clutch then the fault's in the gearbox.

I would guess that you've got a bearing on the mainshaft gone. Get yerself another 'box in there.

[FlatPack]

I think you're right (and I've already had other probs in the gearbox too, so I'm suspicious of it!).

Recon box is probably the way forwards.