Finally I was able to put the ARB locker in the rear axle. I was a challenging task mostly due to the lack of proper tools and, maybe even more, the lack of proper knowledge. Also removing and putting back the third member with the vehicle on the stands in a small garage is not the best experience I had.
Anyway the locker works great: engages easily, no noise from the differential at any speeds… generally couldn’t be happier except one thing. I noticed that the rear axle (in diff area, i.e. drain or fill plug areas) builds up significant heat just after 10 miles of driving (just to clarify: No, I am not driving with the locker engaged). It is so hot that I cannot keep my hand longer than 2 seconds. I have never noticed anything like that with the OEM diff and it really concerns me. How long can the o-rings or pneumatic seal survive in such temperatures?

This heat is obviously caused by friction of something with something. I think there are three possible sources of excessive friction:
Bearing preload is not set up correctly (There is no straightforward instruction in the NSM how to set it up)
ARB dif increased mass and geometry that cause higher rate of fluid shear and cause more heat
ARB dif side and pinion mate gears initial wear (break-in) causing higher friction

The pinion and ring gear are setup perfectly. The backlash and runout are at their nominal values (assuming that the nominal is in the middle of Nissans spec) so I eliminated this potential cause. Also the tooth contact marks look very good.

Here is the question to ARB owners. Could someone “touch” the rear axle after 10 mile (or more) drive. If your diffs are not “hot” most likely I set up bearings to tight.

BTW if someone needs help on install I have bunch of pictures and a few advises. Just don’t ask how to set up the bearing preload…

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vs. ARB