6th gear issue - Pls help

[thegriff82]

Hi

I have an A4 Advant 3.0tdi Quattro from 2008 and having an issue with 6th gear.

When driving along all other gears (1-5) are fine, no noise and car drives smoothly. When I go into 6th gear the drive is still smooth but there is a loud sound from the box, like a rotational whirring sound, take out of gear and it's fine. No pressure on accelerator it's a lot lower sounding but still faintly there, the moment you press the accelerator down it's loud again.

Thanks