chattering noise coming from gearbox?

hi can any 1 help? i occasionaly hear a chattering type noise coming from the gearbox on my m plate v8 disco. got no probs with the gearbox but the chatter? sounds like sumthings bubbling ? recently had a major service inc new diff n gearbox oils any ideas any 1?

Does the noise go away when you push the clutch in? If so i would suspect the noise is from the clutch.

no it happens when im driving occasionally?

I've just had a similar one on my 110. Sounded like it was coming from the gearbox/clutch area when I was driving and semed to happen more on the overrun. Found out what it was when my lad was driving it round a field yesterday. The air filter can was loose due to 2 of the clips having fell to bits. Sounded like it was coming from the clutch when you were inside the cab though.