Absolutely believe that Jeep would do something like that......... just look at the fact that on 4.0 manifolds there is a 75% failure rate around 100K miles........ every auto parts store stocks a few of them, and jeep themselves charges $1200 for the repair!
Take your faith out of Jeep themselves, believe in your own rig!
Does it happen when braking or just coasting?
If it is braking, try using your handbrake and not your foot pedal (somewhere safe)
If the klunk happens with the hand brake have a shop look at your drums(brakes)
If it doesn't happen with the handbrake you would be looking more at a bearing problem or a driveline/differential issue.
I am by no means an expert at this, I have just been dealing with the same issues.
Just find a Meineke or Les Schwab, have them diagnos it, then shop around!
Local auto parts counter guys will usually help point you in the right direction as well, just don't go there in a suit!