HELP!! Popping getting louder
 

My wife's 00 XJ LTD (auto, 4.0L, selec-trac x-fer case, Chrysler 8.25
w/trac-loc) is still popping when it stops. Only when the axle seems to
have been warmed up, though. Doesn't do it cold at all. AND, it doesn't do
the "pop pop pop..pop...pop...pop" as I slow down if I stop abruptly. In
that case it just pops once at the end.

What the heck could this be?!?!? The u-bolts holding the spring packs on
are tight, the shackles are good to go, the rear driveshaft u-joints are ok,
and the drive shaft only has about 1/8" play when rotated. I just changed
the diff fluid thinking that was the problem (yes, I put the additive in
there).

HELP! I need to get this fixed before something bad happens!

Eric