Hi, I have a 1998 Audi A6 2.5 TDi V6 this really annoying noise in 4th 5th & 6th Gears I have dropped the Gearbox Oil & put in new Audi Oil but Noise is still there.

You can hear it on acceleration & deceleration if I dip the clutch noise goes when coating downhill

Can someone have a listen to the files located here :-

FileSwap.com : gearbox 1.wma download free

FileSwap.com : gearbox 2.wma download free

FileSwap.com : gearbox 3.wma download free

Just had new belts etc fitted last week including water pump so it cant be coming from any of that :-(
this is really doing my head in now as I am unsure where its coming from & I want to get it gone,