A few weeks ago I heard an interesting noise when I shifted into 5th gear on my 2000 Xterra.
Then I didnt hear it.

This past weekend i was driving , it was a 500km trip ...half way into the drive all of the sudden the noise came back but it was way louder.
I drove for about 1hr in 4th gear, there was no noise there.

There was no nissan dealer where I was so i took it to a tranny shop, and the guy said the transmission is gone.So i made it back to my city in 4th gear ..yey.

So the Xterra has 113K I think thats around 73000 miles.
Anyone heard of a transmission going after so little milage.

Tomorrow im making an appt with nissan, so they can check it out ..and we'll see if I can get them to replace it.
It is only 13000 KM after my powertrain warranty.
Anyone else have anything like this happen with theirs?

Yes, we've had two of them go in PNWX, both early 2000's same color, and both were replaced at 80K miles, though problems started probably 10K before that. There have been others... do a search in the problems forum. Ours were synchros and (I think) bearings though... sounds like you have a different kind of failure unless you had synchro and bearing problems before and didn't know it.

Did you ever change your own gear oil? If you had little teeth come out when changing then yours started out with synchro failure.

I have one of them here to tear apart and see exactly what happened.