Classic Alfa - Transmission Whine

[Lotobear]

I posted this on the Alfa section but received no commments. Though I'd try my luck here.

1976 Alfa Spider Veloce, 105 series with the 2.0 carb engine and 5 speed gearbox.

The gearbox has a very loud whine/tingling sound at idle in neutral which disappears once you engage the clutch. It continues in drive up to around 2k rpm then seems to go away.

The gearbox gaiters are part missing so there's quite a bit of noise getting into the cabin but this sounds way excessive and very much like a noisy bearing.

Initially I have dismissed the thrust release bearing on the basis that it ought to get noisy when loaded against the clutch whereas it actually goes quiet when you depress the pedal. I'm assuming mainshaft bearing but doing a Google seach throws up this issue as being relatively commonplace and most are of the view it is likely to be the thrust bearing which does not really make sense to me.

The gearbox otherwise seems perfect and even the synchos work properly which is a usual weak spot with this 'box. I'm going to pull the engine and box shortly but wanted a steer as to the likely cause - I can do the clutch and thrust bearing myself but not a geabox rebuild

Any thoughts as to the most likely cause?

[Bennachie]

Thrust bearing. Loading it kills the noise. It is tingling on the clutch diaphragm fingers as well. Less 'goes away' at 2k, more likely you can't hear it..........

[Lotobear]

Cheers for that, should be a cheap fix then.