Lifting it off the ground and taking the load out of the equation only confirms that you have axle wrap. You said that you have a 4" lift, as BB78 asked, do you have lifted springs or lift blocks? If you have lift blocks, take them out and throw them away. Any lift over 2" with blocks is asking for trouble....it WILL fail you at some point. If it is an add-a-leaf or blocks then I would get a new set of springs. End of story. If your springs are fairly new (less than 5 years), check the spring perches and u-bolts. Make sure there is no wear on either and the bolts are tight. If the springs are over 5 years old, or you have never replaced them, I would replace them. If you do, I would look into the Cage leaf packs, they are a better ride and will flex better than any other spring set on the market. If you can't or don't want to go the Cage route, then I would go BC and then Wild Horses. Duff is over priced for their stuff in my opinion for what you get, and they are the same that Cage is, just the older version. The other thing is that you could get ahold of WH and order their "wrap trap", but it is a weld on application that will stop the axle wrap. It is a brace that is mounted between the frame rails & also on the top of the diff housing. But, if it were me, I would get a new set of springs first and then if the problem is still there, then the wrap trap.
So #1 - Check the u-bolts for tightness...#2 - Check the spring perches for rounding. If they are, replace them... #3 - Replace the springs... #4 - Order Wrap Trap from Wild Horses. That is what I would do, in that order.