2001 xj knock from back of jeep at idle?

Someone please help. I replaced my exhaust with a new dynomax myself, thinkin the noise i was hearing was my exhaust. Turns out it isn't and it's not the cat as i have dealt with that noise on my dakota before.

At an idlle, not moving, in gear usually, with the frequency of the vibration of the engine comes a repetative thuddy clunky knock. It's coming from the far back. i got underneath and traced out the whole exhaust thinking that a pipe was juuuust barely touching something underneath as it sounded EXACTLY like that. But there is clearance everywhere.

As far as i can tell its coming from the back back ( super secret xj term there ).

I dunno if maybe the rear hatch has somethin loose inside behind the panel, or what. I really can't trace it.

Someone else HAS to have had this problem and figured it out already right ?

Enjoy a pic i took a couple days ago. Replaced factory steelies and junk sr-a's with ravines and general grabber at2's in 235/75r15 ( FRIGGIN AWESOME TIRES! ) ( daily driver, stuck with factory tire size, and yes 235's fit the ravine JUST FINE )

Specs:
2001 xj, 4.0, 4x4, 104k miles, maintained METICULOUSLY by me mechanically in every detail ( minus a car wash it needs badly )

i know its not the back back, but my transfer case selector lever vibrates at idle, annoying as hell, you just have to move it up or down a little and it stops. maybe that will help

Hello all. Well while fighting with my transfer skid plate last night, i did some more searching around for that knock and i think i found it.
There is a linkage rod coming off the tranny/transfer case that connects multiple linkages to it and acts like a pivot for them. It passes through a 'mount' for lack of a better term which seems to be held to the unibody on the drivers side. The mount seems to either be screwed it or held by rubber vibration bushings.

Anyway the ROD has slop in it as it looks like a very small bushing has worn out. So when the driveline vibrates JUST right, the rod bounces i side the wallowed out baby bushing and causes an annoying knock in the cabin. However i dont know how i'd remove it as the rod passes thru the mount a good inch and i really dont want to remove all the linkages to replace the part. Any ideas ? Here is a pic.

I have the same noise on mine, Havent bothered to look into it yet tho. When you fix it post some pics