Noise only in the 5th course

Good morning, I noticed that with my Phaeton 3.0 V6 TDI, EZ 07/2008 only in the 5th gear when accelerating in the speed range between 1600 and 2000 rpm a screaming noise occurs. It can be heard (I suppose thanks to the super noise insulation) only remotely, but definitely there and in my opinion not normal. It does not occur in the other gears. Only in the 5th gear and also only under load, so when accelerating. However, besides this noise there is no indication that anything would not be right. No shift trucks or any other anomalies. Does anyone perhaps have a tip for me? Thanks already.