I actually had a similar problem, ended up replacing the gears. I had run about 1800 miles before it came out. Took it to my shop, they replaced the gears and said it was a material defect.

What gears are you running?

Superior 5:13s

Look at this picture. If the red circled area is NOT a camera flash, but it the actual wear pattern, then the pinion depth is a tad too shallow. It should be right in the center of the ring gear tooth, and as you can see, it is not. Whether this is causing your noise though, I have no idea since I cannot hear it.

http://i64.photobucket.com/albums/h2...team/gears.jpg

if you're really concerned with how the pattern is meshing, I highly suggest you get some gear marking paint and paint it on those gears, then run a proper pattern for us to see...with the axle fully assembled like that it will be super easy to run an accurate pattern as you require about 50 ft/lbs of drag on the carrier to get a nice pattern, easy done by lightly applying the brakes while spinning the drive shaft back and forth through the paint a couple times. Just head to your local gear or driveline shop, they should have all the paint you want