I've got an AU series 2 with LSD that has this exact problem since I bought it. Can't tell what side it's coming from, but if I had to guess, I'd say the right side.
Driving, sometimes it comes, sometimes not.

Mostly you hear it when you come from a high speed, down to a low speed, such as ~30km/h or when cornering and braking. I've never heard the noise while the wheels were under load.

It's been doing this since I bought it 2.5 years ago, which was roughly 50,000km ago.

Al I did was change the diff oil with some high quality stuff, and there weren't any metal flakes in it at that time. That was about a year ago now, and the noise has not got any worse, nor has it got any better but as I said, it comes and goes.

I'd say just drive it normally, see how it goes, have a secondary one lined up just in case. I had a second hand LSD and non-LSD priced at a local wreckers, and they wanted $280 for non-LSD and $370 for LSD - that's before installation costs however, but if you're lucky enough to have somewhere to do it, you could probably do it yourself. (maybe, how mechanically minded are you?) I wish I had flat ground to work on mine lol, it's nothing but gravel or hills here. the flat ground is gravel - can't use my trolley jack on that.