I had an 86 Pathfinder. When changing from 4 to 2, or from 2 to 4, I had to
be fully stopped. Then I had to roll the vehicle in the opposite direction
about 3 to 5 feet, then forward again to make the hubs engage.
From my experience, it sounds like you may have stripped the engaging gears
in the hubs. You should take it in and have it checked. There are no second
chances when they don't engage properly. I had to replace them about every
few years on the Pathfinder. I broke them a fair number of times. Here in
Canada they cast about $200, including the labour.
By-the-way, the Xterra is a great off roader! I've tried one, and I like it
very much.

Signature
JANA
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I bought a used 2000 xterra se with a manual transmission a couple of
weeks ago. I havent had any problmes until yesterday when I tried to
shift the car from 4wd back to 2wd.
After driving uphill on an unplowed snow road I stopped once I got the
main st. intersection. I shifted the system back to a 2wd and I
started to drive the truck again a horrible loud grinding noise emerged
from the truck. The noise went on for a good 5 to 10 seconds, I couldnt
stop since i was in the middle of main road, and then, I heard a very
loud BOOM and the truck all the sudden was fine again.
It appeard to me that 4wd system got stuck going from 4wd to 2wd. Is
this normal in the xterra? I drove a 94 pathfinder for many years and
that never happened. . I am really worry about engaging the 4wd system
again. Should I be worry? Has anyone experieced something similar?
Please your input is greatly appreciated.
Thanks