Whining...gearbox i think

My 1984 gti cab had a very intermittant whine from about 2 months ago. Well it's not so intermittant now so i think i need to sort it. Basically between 2-3000 RPM the whine starts and gets louder with the revs and when i dip the clutch it stops. Occasionally it dosen't do it but it's getting more and more frequent. Could it be anything other than the gearbox? I replaced the oil a few months ago and i've checked it's full. The clutch seems to have had it aswell so might be a good time to change the box. If it is the g'box could any1 recommend a good rebuilder or a any1 have decent box for sale?

Also what gearbox code should i be looking for the one that's in now is FM 07110

Thanks