[Tanoc]

The majority in that statistic are selectable 4WD, which isn't the same as AWD. Pushing the two groups together skews the numbers a bit. Most trucks since the 1970s have been 4WD, ever since companies like Muncie and Borg-Warner started selling axles to Ford and their cohorts. AWD trucks are a relatively new phenomenon, with the first one I can think of being the limited production GMC Syclone in 1989, and it being a truck was an emissions loophole. I think the 2005 Honda Ridgeline was the first real mass produced AWD truck, or perhaps the Subaru Baja from 2003 if you consider that a truck rather than an open deck car. Right now I think only the Ridgeline, Hyundai Santa Cruz, and Ford Maverick are sold as AWD, whereas every other truck is selectable 4WD.

[wil421]

Push the goal posts of you want. OP specifically said rear wheel drive.

There’s a whole community that doesn’t consider anything without front and rear lockers, dana 44 axels, frame on body, and 37s with bead lock a real off road rig.

[Tanoc]

There is a difference between AWD and 4WD, because 4WD trucks are RWD until you manually change the mode. AWD is all on all the time and is FWD biased, usually something like 70:30 F:R. For most of their lives, even when towing, 4WD trucks are used as RWD only. As for specialized off-road vehicles that wasn't what we were talking about, but yes those people split hairs down to the micron for what constitutes what.

[benlivengood]

There are so many varieties of AWD. Most are wet-clutched (inside or outside of the main transmission), some are lockable or torsen center differentials, Prius adds electric power to the rear wheels to complement the FWD hybrid setup. Traditional 4WD with a transfer case using a manual shifter-actuated gear selector isn't very common any more. My 1999 Suburban had a wet clutch in a standard truck-shaped transfer case, one side of the front differential had a solenoid to lock/unlock one wheel to the side gear to keep the front drive shaft from spinning in RWD mode, and used a motor to mechanically engage or disengage the wet clutch (between the front and rear outputs) and to slide the engagement ring to offer AWD (rear-wheel biased, engaged when front and rear wheel speeds differed anywhere from 0 to 100% torque transfer) or 4WD (clutch fully engaged), and even 4WD-LOW by running the motor the other direction to engage the planetary gearing with the rear drive shaft.

In my mind, the biggest difference is whether front and rear drive shafts turn at exactly the same rate; if so it's "4WD". If clutch slippage or a differential allows different front and rear axle speeds then it's some form of AWD. But many AWD systems have clutches capable of effectively locking the front and rear driveshafts. E.g. the Suburban had tire-hop turning on pavement in 4WD mode which is about the most torque that drive-train would be expected to encounter.