[B D HEMI]

Got a problem , as I was driving a loud howling noise came from my engine / transfer case area . It stopped and started all over again . Don't know what the hell it is but it comes on and off and wondering if anybody has any idea what this could be ? I pushed the gear lever into neutral and the howling noise still continues . CV joints ? transfer case ? drive shafts ?
Appreciate any help here .
B D HEMI