Yep mines has been like that since day 1. If sitting in standstill traffic I notice it alot. I think alot of the noise comes from the diff, driveshafts, propshafts etc. I think its just all losely put together and this then echo's into the gearbox. Mines makes a whining noise also when in first and I left off. Its not overly loud, just like an electric motor slowing down.
I took mines back to nissan to try and get a new box but they told me to ram it
When I put new fluid in the diff and gearbox along with molyslip it quietened it a little but i think the dual mass fly makes alot of noise which will add to all the clangs and clutters.
I honestly wouldnt worry to much about it, even though it is embarrassing. The noise has made me kangaroo a few times try to make it quieter lol.
Might try molyslip see what that does...no noise at all whilst engine is idling, just when i lift off throttle and car kangaroos of its own accord and with each hop you hear two pieces of metal clanging together. Also get the noise when playing on the biting point and engaging the gears.
The dual mass is designed to absorb the shock from the drivetrain and gearbox etc thats why it makes noise i'm sure