Nissan Patrol 4x4 (Africa)

As far as I can recall the two breather pipes run from the top of the auto and transfer box on its left side(passenger) then onto the left side chassis and then all the way up to the upper front wheel arch. You will have to take off the inner wheel arch covering and various clips to get to it. I left them as is as it's pretty high up in the arch bay.
I blew clean air through them to ensure they were not blocked a few months back when I did a service.
My patrol did however have the diff breather pipes extended by the previous owner.

Front diff, gearbox and transfer case breathers go up into the wheel-arch as described by NMAD.

Rear diff breather only goes into a chassis cross-member. However, I have had water in my gearbox (on the manual gearbox there is a boot where the lever enters the box, and I suspect mine is perished) but never in my rear diff.