Steering Popping Sound

ok when i turn my steering wheel to the left 2 inches as soon as i turn it back to the right i get a clunk, also get the clunck when i turn back to the left, so i get a clunk basicly whenever i change direction with the steering wheel, everything on the front end is tight no worn ball joints no frame cracks at steering box, i can feel it on the floorboards and when i lay under the jeep it sounds like its coming from the firewall area, anybody ever have to replace the ujoints on their steering linkage from the firewall to the pwr steering box?

TIA

[ my xj does this when the track bar bolt in the bottom bracket gets loose. usually after some heavy 4x4. watch the track bar where it bolts to the bottom braket and have someone turn the wheels all the way to one side then the other. usually you can see and here the pop when you start the other direction