FINAL RESOLVE... local FoMoCo service dept finally fixed.. This is what they did in sequential order to resolve the problem 1: replaced driver side front wheel bearings, 2: replaced all ball joints (not related to problem but under service contract, 3: replaced passenger side 4 wd locking hub (locked in on position) 4: replaced drive line u-joints and finally (6) had drive line balanced.. problem went away after item 6. Thank goodness for service contract... Just posting this for information if others experience this same problem.