I don't think it is conclusive the cause is the motor mounts. It could be transmission related or transfer case related. I would do more trouble shooting such as checking to see if the transmission is at the proper level and making sure the fluid was per specs since it was recently changed. And get the help of someone, secure the vehicle and see if you can find the source of the sound.

There will be excess engine movement when the vehicle is in drive and held by brakes and the engine RPMs increased.

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X5 4.6 2002 Black Sap, Black interior. 2013 X5M Melbourne Red, Bamboo interior
Dallas