So my friend recently (3 days ago, AS IS) bought a 2002 nISSAN Xterra base model w/ 4wd (STD transmission)....I noticed twice as he pulled away a clicking noise coming from the passenger front wheel. It almost sounds like CVjoint noise to me but it happens in straight lines and comes and goes sometimes. Since the sale was so recent I told him to call the seller and see what he might be able to work out (sometimes the power of persuasion works). What could be the issue with it? Also, twice it has not started on them, alsmost like the signal wire to the starter wasn't hooked (i'm going from my experiences as I know next to nothing about the Xterra) or the relay that sends the starter signal is shot.....Anyone know of these issues???

Okay so I figured it out.......the locking hub for the 4wd was not on "free" or "4wd/lock" so it was somewhere in the middle just clicking around...

If it was the hub there are 2 reasons for it.

1. The hubs internal mechanism is damaged from the 4WD lever being engaged at a speed over 20 MPH. This can cause the metal plates inside the hubs to twist and prevent proper disengagement. And if this your friends first 4x4 with auto hubs there is one thing he should be made aware of. Even though it is possible to switch from 2WD to 4WD mode while moving forward it is better to be fully stopped prior to switching to 4WD and once 4WD is engaged to drive forward slowly at first to allow the auto hubs to engage fully.

When switching back to 2WD. Stop the vehicle. Move the transfer case lever from 4WD back to 2WD and back up 5-10 feet to make sure the auto hubs are fully disengaged.

The second item that can cause a partial hub disengagement is the hubs need to be taken apart, cleaned of all the old grease ad inspected for water damage (rust) or mud and if they check out regrease them and reinstall. ( Be sure to get a new o-ring seal from the dealer so the hubs stay water free.

PS: Hubs should be removed and inspected at least once a year and serviced at a minimum of every 2 years. Service intervals will shorten if this Xterra sees moderate trail usage.

Sounds like you have manual hubs from that description. Do you?