strange noise (sort of friction) on Golf MK IV
 

The car is a T reg Golf Mk4 1.6 S (AEP 8v) with 65k miles and FSH.
When I am driving with gear engaged and I let go the throttle I can hear a weird friction noise coming from the centre or front of the car. When I accelerate the noise disappears, but whenever I let go the throttle It comes back again. It seems to be loudest on 3rd and 4th gear. And I think I can also hear it but very slightly when I press the clutch, especially on 1st gear. I have done some research and I heared that it may mean that the whole gearbox needs changing . Please tell me it something less serious

P.S Sorry for any language mistakes but English is not my first language.