1997 Jeep TJ Cyclical grinding noise

Ok so here is whats going on with my 1997 jeep tj, I have been chasing this grind and dead spot since I purchased it ( dead spots good now ) so it has new u join's both front rear and axle u joints, it has new ball joints, tie rod ends, track bar and steering box and all new fluids ( oil, tranny, transfer case, and both differentials power steering and coolent). I have a grinding noise while driving over 20 mph, it is only after driving for a bit, if I let the jeep sit for a week with out driving I can usually get 20 mins before grinding occurs. It it is not affected by the engine if I drive down a hill with the engine off the noise occurs, the only time the grinding dissipates is when turning right. Also there are random popping ( happens like once every 1/2 hr or so) and the vehicle will jerk left or right like one of the wheels as stop spinning, but it only happens for a split second. ( First time it happened thought I blew a u joint) I have now taken it to three different shops and none can tell me what it is, It does have leaking rear pinion oil seal though, But its like the sound is comming from the center front of the jeep, if I sit in the passenger I would suspect the driver side and if im in the driver side it sound like the passenger I am at wits end now. Please help if you can