I had this problem with my 4/4. being as my doctor calls me Obese when i went over bumps, accelerated hard or on undulating roads the prop shaft the casing under the seat and went off like a machine gun. Very Disturbing.
The solution was to fit 4 seater springs and anti tramp bars.
unfortunately the factory only fitted one Anti Tramp bar on the drivers side.so at low speeds going over speed bumps the passenger side does tend to bounce.
so anti tramp and 4 seater springs have solved the issue.
