What would cause a loud clunk/vibration noise when shifting into reverse only.

Possible engine//transmission mount(s)... Exhaust pipe hanger issue... Suggest having vehicle hoisted on a *drive-on lift* and visually inspected as it's being shifted to locate problem.... Drive-on lift keeps the vehicle and suspension setting just like it would be if it were sitting on the ground but allows for easy, more detailed inspection! .. Alignment shop should have that lift... Some general auto repair shops do as well.