Just got mine yesterday, and noticed what I think of as a 'gravel in the gears' type sound at low RPM. I can't open the attached file, but this might be the supercharger, not the transmission. Not sure if it is normal.
Sounds louder and more ‘gravelly’ than mine did on my Evora (same engine, same supercharger). The coupler can go (it did on mine), but it didn’t sound like that. The only other thing that can go is one of the bearings.