Thanks guys the vibration feels like its below me seems to only happen if u give it full throttle or close to it to make it drop gears

Hi all, New to p38 ownership and to 4x4 ownership but when im driving along and give it full throttle there is often a vibration and noise for a few seconds any clues to cause or advice woukd be apreciated. I have a 2000 4.6 model