All Wheel Drive

Most of these AWD models have a viscus clutch in the transfer case between the front and rear drive shafts, (think fan clutch). This allows some slipage, for turning on pavement for instance, but transfers some power to the other front/rear drivshaft. The more slipage the more transfer. Some of these can be locked--most do not.

The new ones do. It was the older ones with " full time 4wd" not AWD the grenade.

Mine locks up very quickly in AWD...

Which is one reason the old auto 4x4 transfer cases would grenade regularly; their slow engagement time allowed the speed differential to build up too much.

My 2015 Yukon Denali has 2wd-auto-4wd-4wdLo. It works exactly as my 05 1500 did in that in auto when the rear spins it locks the tcase up. In my 05 there was a pretty good delay before that lockup.

There seems to be a little confusion, most of the 1/2 ton in the market have a system that is BOTH quasi-AWD AND 4x4. My Expedition has this, and the Tahoe I test drove at the time was the same. It has 2WD, 4Auto, 4HI, 4LO. The transfer case is a 2 speed and locks the drive shafts together in 4HI and 4LO. Do not drive on pavement in either of these modes.

In 4Auto a variable clutch is used to allow slipping, it is designed to be driven on the street. 95% of the torque is still transfered to the rear. The computer measures the front and rear driveshaft rotations and if there is a difference the clutch begins to transfer more torque to the front. You can sometimes tell this is happening because on a low traction surface you may feel a slight bump and grab as rear starts to slip and torque is transferd forward.

The above system is not true AWD which divides the torque evenly all the time while still allowing slipage (think Subaru, I still miss mine :() I am not sure abou the most current Yukon Denali, but what I have read about the GMT-900 generation, the AWD left something to be desired. The Navigater AWD is just a 1 speed version of the above Control Trac system.

The Explorer 4x4 I had previous did not have 2WD option, only 4Auto 4HI 4LO. I towed my sig TT with it and never had any issues with it being in 4Auto. In fact, I loved it, and when towing will often select 4Auto on the Expedition. That way if I get into a limited traction situation I don't even have to think, it just works! For example, pulling onto a highway from the roadside fruit stand, there is no one wheel burnouts in the dirt trying to keep from getting run over, just point and press the go pedal. It has also saved my bacon on a patch of black ice.

I would opt for the 4wd so that 95% of the time I can keep it disengaged. Then for the 5% of the time I need it its only a pushbutton away. I always opt for 4wd with lsd which I believe will outperform any AWD system either on or offroad when engaged.

FYI I have never needed to engaged 4wd when towing the camper. (yet)

Terryallan wrote:
Just so you will know. You cannot tow on dry pavement with 4x4, and shouldn't in the rain. True 4x4 will not allow the wheels to slip independently of each other, and will put the drive shafts in a bind which will put the trany in a bind, and cook it.

You can tow on any surface with All wheel drive, as the wheels can turn independently of each other

^^^ This. Do NOT drive a true 4x4 on paved roads. The question is whether you want offroad capability or on road capability, like driving on wet or snowy roads. If you want offroad capability, you really want 4X4; AWD is decent at best for that. If you want more control for driving on the road, then get the AWD. The 'better' system depends on what your goal is.

Many years ago I had a Chevy Astro AWD extended van. It was great for towing (within its weight limits). I prefer AWD for 99% of road conditions over 4wd. 4wd doesn't really excel until you get off road and even then a good limited slip differential or locker makes a huge difference.

I wish I had an unlockable center differential in the transfer case of my pickup for snow and ice conditions!

If you can afford a 2007+ GMT900 Denali, that would be a very noticeable improvement in power and 6-spd transmission gearing vs. 4. The AWD has been very reliable since its introduction and shows no specific sign of extra wear or handling compromises when towing.

Keep in mind the payload of the Denali is relatively low for its tow rating. It you are considering towing 6k+ dry, you should consider the 3/4 ton Suburban/Yukon XL.