Someone at CT asked this today, so I thought that I'd post some of the info up here as well. Follow the links for more information.

A transfer case is a part of a four wheel drive drive system found in four wheel drive and all wheel drive vehicles. The transfer case is connected to the transmission and also to the front and rear axles by means of driveshafts. It is also referred to as a "transfer gearcase", "transfer gearbox" or just "transfer box".

http://en.wikipedia.org/wiki/Transfer_case

There are almost as many different types of four-wheel-drive systems as there are four-wheel-drive vehicles. It seems that every manufacturer has several different schemes for providing power to all of the wheels. The language used by the different carmakers can sometimes be a little confusing, so before we get started explaining how they work, let's clear up some terminology:

* Four-wheel drive - Usually, when carmakers say that a car has four-wheel drive, they are referring to a part-time system. For reasons we'll explore later in this article, these systems are meant only for use in low-traction conditions, such as off-road or on snow or ice.

* All-wheel drive - These systems are sometimes called full-time four-wheel drive. All-wheel-drive systems are designed to function on all types of surfaces, both on- and off-road, and most of them cannot be switched off.

Part-time and full-time four-wheel-drive systems can be evaluated using the same criteria. The best system will send exactly the right amount of torque to each wheel, which is the maximum torque that won't cause that tire to slip.

Pretty pictures here:
http://auto.howstuffworks.com/four-wheel-drive.htm

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05 KC SE Smoke
01 Suzuki 600 GSF
88 Fiero 2M4

Help,
My Manual Shifter on my 2004 Titan doesn't work. And the front shaft turns even when in 2wheel drive mode. What the heck is going on?
Glenn

Hmmmmm we need more info. What do you mean the shifter doesn't work and how do you know the drive shaft is turning in 2wd?

And what manual shifter are you referring to?

Red

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2005 Titan KC SE, Helwig, True-Track, ARE MX Canopy

Well, it sounds like he's saying that he's got a shifter on the floor for 4wd... but I thought all the Titan's were electronic 4x4?

It almost sounds like his hubs aren't unlocking?

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05 KC SE Smoke
01 Suzuki 600 GSF
88 Fiero 2M4