Back again--the problem is all but gone (low frequency rumble in AC) but is still a bother when it does show up. It has happened after the car is turned of following heavy A/C use. This leads me to some sort of chatter in the expansion device when equalizing pressures. The clunk/rattle noise was the transmission side motor mount cracked up under battery cable tray/wiring run. Easy enough to change.
Any assistance will be appreciated. No other noise from any other component and the AC is ice cold. Just that rumble--I may stick some cloths/sponge between the expansion device and fire wall to see how noise changes. Next step appears to be change out expansion device. Thanks again--oh-the fans seem to be just fine.