searched... wanted to clarify.
 

My 04 4.8is makes a big (not like earth shattering, but very noticeable) clung/thunk/thud call it what you want when i mash the throttle from a stop. hill or no hill. sport or not sport mode. is this in fact the "phantom rear ending" people speak of?
i hear the software update fix is available for the 4.4s, what about the 4.8s?
anyone experience this? i have 46k miles.
again, i searched, but it seemed to only apply to a 4.4, not the 4.8.
thanks!
charlie

come on someone has to know what im talking about.
just looking to clarify

It's probably the AWD system moving power around so you don't lose traction off the line or a worn out suspension component

get the software update from bmw. ask for any software update that is avail for the 4.8

The sound you're describing doesn't seem related to the "rear-ended" issue. That issue presents itself when coming to a stop, not when mashing on your throttle. Have your front suspension inspected or get underneath and look for the condition of the thrust arm bushings. The sound you described sounds related to your front suspension.