gear box noise ?

hi i have a vauxhall cavalier 1.6 its got a f13 gear box i had the gear box overhauled about a year ago because it was noisy in gears now it got a slight whine in all gear i have changed the oil and it made no difference but if labor the engine you can really hear the whine but if u drive normal you carnt really hear it but its there . wean driving and on the gas the noise is there as soon u get off the gas it stops or dip the clutch down wean driving it stops any ideas ?? thanks could it be a clutch barring or diff barring ?? if you have any ideas can u email me on adam.little2@hotmail.co.uk thanks very much