Below 20mph she has little to no noise 30 - 40 mph it gets very loud, the tone may change but she makes noise when accelerating or coasting, I've added a picture so you can see some of the different ways the contact patch can be wrong

Do yours look like any of these? If the drive side is off the coast side will be as well. I was under the impression that the drive side looked good.  Do you have an images of the drive side being good and the coast side being off?

I did think the drive side was good but compared to the pictures of a good contact patch it looks like it's to thin, it looks like a combination of the bottom left and bottom right in the picture, I do have a picture but it's not very clear

tough to say. I guess your best bet is to change until you feel it is better. looks like there isn't an adjustment or shimming for the ring gear.  The pattern looks pretty uniform and centered on the drive

One day I'll have another look it's not a big job to take the diff out, the patch looks a bit small to me plus the coast side the patch is on the toe of the tooth, I'm assuming as the contact is off a bit that's maybe what's causing the noise, it give's me a little hope that I can improve it (picture of ring gear shims)

[2015 Z Force 800 53/Trail EPS]

I forget..what exactly does that adjuster do that's on the outside? I was looking at the breakdown some months ago but never fully understood. Shims on the carrier and pinion I get..but the adjuster is still somewhat a mystery to me 

If you are getting clean diff fluid on your oil changes, I wouldn't mess with it personally.

I know what you mean but I'm fussy and I've almost ironed out the gremlins, if I could sort this out I would be very pleased. The adjuster on the outside if for a ring gear support, It's to stop the ring gear moving away from the pinion gear under stress

[2015 Z Force 800 53/Trail EPS]

I know what you mean but I'm fussy and I've almost ironed out the gremlins, if I could sort this out I would be very pleased. The adjuster on the outside if for a ring gear support, It's to stop the ring gear moving away from the pinion gear under stress

Oh..so does it actually touch and ride against the ring/crown gear in normal operation?

No, it's set with a feeler gauge after setting the lash, can't remember the gap measurement is

[2015 Z Force 800 53/Trail EPS]

No, it's set with a feeler gauge after setting the lash, can't remember the gap measurement is

Ok..I think I remember reading something like that. Thanks

I returned my Zforce 800 a week after I purchased it as I told them I could not tolerate the noise from the back end.  This Z was my second SxS so I knew that noise wan not right.  I took the mechanic for a ride and he confirm the noise and actually said it sounded like a wood planner especially while accelerating.  I left it with them and returned a week later.  Now I am no mechanic but they told me they ordered in some new shims as the diff was too tight. I took it for a test drive before leaving and the noise was no longer there.  5000 km later and still no noise   :-)

Would be interesting to know what they done

So the adjuster rides on the back of the ring gear only during high torque loads?

It doesn't touch the ring gear but the gap is very small, just for when very high loads are applied, there was no sign that mine had ever touched the ring gear