2016 DCLB AT front diff noise, in 4H only, with BDS lift

Looking for advice on 2 things please.

#1 Looking for advice what this might be?

My 2016 with 85,000 kms has developed a minor whirring noise whilst in 4H at hyw speeds. Noisier upon accel or decel and prominent at 108 km/h. I feel it in my feet and in the steering wheel and again very minor. Its not a grinding noise and likely not a bearing as it comes and goes. No noise at all in 2WD so im guessing its not T/case.

#2 looking for advice on how i might approach the dealer.

The truck still has 15,000 kms of powertrain warranty but here in lies the rub. My truck has a 4 inch BDS lift on it so the crossmember has been replaced. The only warranty item i have had completed is the ECM reflash, so hoping that maybe they might consider providing some assistance.

Appreciate any help -- Merry Christmas