I also have the reduction gear noise. It has been getting worse over the last 12k miles (started at 59k). It is now bad enough that my passangers almost always will ask about the noise.
I am pretty sure it is the recduction gear as I have already replaced the Wheel bearings, driver side axle and performed the TSB for clicking. I have replaced the reduction gear oil. It was black with plenty of particles on both magnetic plugs. Several others have reported the same.
It is a little surprising that a simple reduction gear would have any problem. At this truedelta web site, they report a 3% failure rate on the transmission. https://www.truedelta.com/Nissan-LEAF/t ... oblems-968
I have priced a new Reduction Gear at my local dealer at $1600 (not installed) or $300 from a salvage yard. Neither Nissan or the after market suppliers seem to have a "rebuild kit" for the reduction gear.
Before going after a replacement, is there any experience from the forum with this problem or are there other recommendations?