IM diffo no expert but i have the same problem an was told i need new rear diff mounts, a local lr specialist could atleast confirm that for you or get it up
Hi
New Rear Diff last march, plus all new diff mounts, swapped the drive shaft for 2nd hand unit that was in better condition this march, replace the rear LH half shaft around the same time (new). Metallic sound now happens in 2nd, 4th & reverse. And more recently under heavy acceleration when trying to pull away fast !! ? could still be Diff' mount but can't get any movement, I'll get it check any way.