Well I was stock in mud and I noticed that the not all 4 wheels were turning and grabing. Why is that? I thought that is what 4x4 is for when you go on 4 low it should grab with all four wheels, but not. What the heck? I am all new to this off roading business, but I do like it, so can you explain to me why is that happening?

Thanks!

That is because the Xterra has a "limited-slip" rearend as opposed to a "locker". What that means is that on the limited-slip the power goes to the wheel that is "slipping" the most. In a "locker" rearend both the wheels are "locked" into spinning at the same time. Power goes to both wheels equally.

More....

The reason it is is a "limited-slip" is for its drivablilty in everyday driving (especially turns on pavement). You do not want to drive a "locker" everyday. It will wear parts and tires.

Stone

4lo is no different than 4hi, other than the overal gear ratio. Engaging low-range doesn't change the way the power is distributed.
Without true locking differentials (or no differential at all, a "spool") your Xterra is at best only 2WD when the going gets tough, one front wheel and one rear wheel. The nature of an open (or even our lousy limited-slip) differential is to send most/all of the power to the wheel with the least traction on each axle. One side will spin while the other side does nothing. The limited-slip unit in the rear helps to keep a wheel from starting to spin, but once it does the power left to the other side is minimal and usually not enough to push or break traction, though in mud it's usually slick enough to have both rear wheels turn.

Brent

Ok I got it though I think that in this case the 4x4 does maybe a little more then a regular vehicle.
So my question is can you add some after market part to have those differentials locked when you need it?

Yes, you can put lockers in the front and rear and next time you get stuck all 4 wheels will turn.
If you only have a locker on the rear then 3 wheels will turn (2 in back 1 in front).

If you're like me and you need a visual explantion to see why only 2 wheels turn then go here:
How Stuff Works

Will I sacrifice a regular - daily reliability with this "lock"?
Who sells it? How much?

Thanks!

Check out my FAQ section of my website. It was written for 4Runners, but the off roading part still applies. It's near the bottom.

http://robinhood150.tripod.com/4runner/id13.html

Steve

With a selectable locker (ARB is our only option so far) there are no drawbacks to on-road use since it's as if it weren't there when it is turned off. Actually, you do lose the limited-slip in the rear end which can be a problem on snow/ice when trying to keep moving since using the locker is not advised in these condions.

Brent