rear end makes bad thunk when on incline and put in gear

Vehicle is excellent EXCEPT when on an incline and placed into gear, makes an incredible loud "thunk" in rear end. The whole vehicle shakes...like the rear end is about to fall out. Never had another vehicle to do this/have this type of mechanical dysfunctional problem. The first time it happened I jumped out of the car thinking the rear end had been jerked out! Took it to the Honda dealership and their response was, ..."Oh yes, all Pilots make that noise." You gotta be kidding me!