Over the months (years?) I have been following your posts of the noise.
You now post a LOT of places where you can hear the noise.
A small place like yours or other driveway where the noise occurs would be the best place to find the problem. Why not find a particular place where it occurs every time thus and such is done. Get out and have your friend do that act over and over while you attain various positions around the Jeep to find where the sound is made..
From the distinct sound and location you have written about I'd first guess a shock tube. Either something is loose and hitting it or something inside is loose. But that is just a first guess. And also my understanding of the particular sound..
Big JIm <img src="/forums/images/graemlins/pfft.gif" alt="" />