Unstake the nut, crank it down to 90 ft-lb and restake the nut.

Excellent! Sounds easy.
"So easy even a caveman could do it". But we'll see...

I gave the output flange nu ta good inspection. Nothing obvious. However while banging on a screwdriver to unstake it (is there a speacial tool for this?) I did realize I could wiggle it a little, but not much b/c of the staked-in part.
Sicne teh nut threads were kinda scored from the stake, I replaced the nut at 90 lbs.... pretty much the same position as the old one. BTe I think I was wrong about the "wiggle" - it' will rotate about 1-2degrees either way, slop in the gears I guess... but not really side-to-side at all.
And the noise still remains. It is not as loud now, and I have to be going pretty fast (>70) to elicit it. 70 is just a guestimate b/c my speedo is questionable.

I am out of ideas. Since I know it only appears with increased driveline angle, as a temporary fix, I think I will try and lower my back end ~1". Meanwhile, do a small body lift (1"?), then the 4crawler engine mount lifts by the same amount. I'll have to do teh math, but hopefuly thsi will angle the tranny output angle down a little, enough to make it go away....

For sure you want to check the alignment of the driveshaft flanges:

http://www.4crawler.com/4x4/ForSale/Shims.shtml#FAQ1