can still adjust diff from full open to full lock, so its operating normally. I can make it lock up and clunk if i roll it forward out of FULL OPEN. Its just strange that the noise comes only on decel, off throttle. Which makes me think its a failure of something internal. I think i'm just going to have to drop all the fluids and check for metal.

It's either JDM 04 or JDM GC8 DCCD centre, i'm unsure.