Same issue here. Thought I had cured it, but no luck. Mine is noticable when I make a sharp turn under exceleration from a stop (for example, making a right or left from a stop sign). I do not feel it in the steering wheel, however. It sounds like its coming from the front. Sounds can be confusing when they bounce around a cavernous space like a SMB. My front drivetrain is all spec'd and working properly (replaced bearings thinking that was it, broken hubs, etc.). So, what could it be? Although it sounds like the sound is upfront, I'm wondering if its the rear drive shaft. When turning, there are some flex/changes in alignment of the drive train. That flex might be all that is needed to make the issue noticiable (the clicking/clacking sound). Our rear drive shafts were not designed for the angle at which the 4x4 mod operates, in my opinion (the SMB 4x4 mod anyway (don't know anything about the others) -my Altas is to the rear of the trans, via an approx 8" adapter, so my drive shaft is relatively short). I have the new replacement u-joints for the rear (just haven't replaced them yet as need a strong shoulder to pound the old ones out). When I bought my SMB, it came with a failing u-joint, so the rear driveline has been suspect since the get-go for me. I'm considering a custom rear driveshaft from Tom Woods: http://www.customdriveshafts.biz/index.html
or Arizona Drive Shafts (although their shipping is slow) http://www.arizonadrivelines.com/
If that doens't cure it, oh well, at least I'll have a bomber driveshaft with 1410 u-joints (like F-250/F-350s) instead of the undersized 1350 u-joints.
Silly question and I guess I should have asked it first, can you get the noise to happen when in 2wd? Mine happens when I'm free wheel'n (thus the rear drive line conclusion).