I don't know why I compulsively reply to these threads... there must be 10,000 threads explaining this.
All V8 trucks have the same transfer case for all 4th gen years.
All V6 trucks have the same transfer case for all 4th gen years.
Bossman linked a video that shows how they work.
The only difference between the two cases is the V6 has a 2WD mode. There's even very little physical difference between them, they have a similair model number (that I don't recall at the moment).
When the V8 is in "normal" mode, and the V6 in 4-hi, they are "Full Time 4WD". You can probably just call it AWD, but some people will split hairs at the difference. Reality is, all 4 wheels get power. The center differential gives a 40/60 F/R torque split.
4-Lo on both models obviously is low-range.
Where the confusion comes from is that the center differential's locking engagement is a separate function, separate button, that's not located on the range dial you're referring to. Push this button and it locks the center diff to engage "part-time 4WD", in the traditional sense of a Jeep/pick up, where it cannot be driven on dry pavement.
In essence, you can drive around on dry pavement in 4-Lo in your V8, as long as you haven't locked the center differential. It's handy on a rare occasion.
Anyway, play with the buttons, you'll figure it out. The dash will tell you what's up and the owners manual explains what all the messages mean.
As for axle differential locks, (and someone can jump in and correct this here...) IIRC, there's only one year, 2008 I think, that had a "Trail Edition" that had a rear diff locker. It's a super rare piece.
Regardless, there's 3 differentials in all 4th gens (front/center/rear). Only the center differential can be locked from the factory. Just to be clear on this... other posts/threads seem to generate plenty of confusion about this.
