A question from a 4x4 newbie:

I know the basic differences between 4WD and AWD (no center diff for 4WD, no lo gear for AWD) and that all of the off-road setups that I know of are 4WD.

I understand that the center diff is what makes AWD the superior setup for on-pavement situations (at least where turning is involved), but are there off-roading situations where NOT having a center diff is beneficial? Rock crawling, etc?

Or is it even possible to integrate a transfer case with a center diff?

Are there any vehicles that employ both 4WD and AWD?

Thanks for the info.

The difference between AWD and 4WD is simply that AWD implies "full time". Both have some sort of center differential, though configurations can vary greatly.

The center diff is just used for getting rid of the binding that occurs between front and back wheels, I'm sure you know that.
With a Part Time setup you have the wheels slip which has the same effect.

So when you're in a situation where the wheels can slip the two systems are pretty much the same.
However, just like in an Automatic Transmission the fluid coupling (center diff) on the AWD looses some of the energy transfered from the engine to the wheels. Since the drive train isn't solid from the engine to wheel you can't apply the torque needed in some situations.
Plus factor in having the front wheels go up a steep ledge or other obstacle the center diff will drain even more power that should be used up front to climb the wheels over the obstacle.

Sorry I can't make it less complicated, just try to visulize it in your mind.

AWD systems tend to use a viscous center diff setup, but most real full-time 4WD and even some part-time 4WD trucks/SUVs that don't cater to the soccer-mom crowd have good-old "hard" center differentials that don't sap any power.

Brent

Ah, thanks. That makes sense. Appreciate the info.