All of the confusion is basically around the semantics of this discussion... people with true knowledge of physics will agree that if a tire is in the air, it can do no work as it is not appying force. Maybe a different explaination will help... without worrying about what percentage of "power" is going where.

If a differential is "locked", regardless of where your wheels are, both sides of that differential will rotate at the same speed... whether it's your front, center, or rear differential. Think of "locking" as physically connecting the two shafts the differential is connected to. When speaking of an "open" differential, you could say that the "power" will go to the wheel with the least amount of resistance. Ever turn a corner and punch it in a rear wheel drive car and have the inside tire break free and spin? Ever try climbing a gravel hill (in a vehicle without A-TRAC) and have the tire that starts to come off the ground break free, spin, and leave you stuck in that position? That's an open differential sending "power" through the path of least resistance. A locked differential will keep both sides rotating at the same speed... if one tire comes off the ground, it can't spin any faster than the other tire (same axle, of course) that's on the ground. Our 4Runners have "open" differentials, but utilize the vehicle's brake system to grab the slipping tire and force "power" across the differential to the tire with more traction.

I recommend experimenting with your 4Runner in an off-road situation and watch some real rock-crawlers for an understanding of what it means to "lock" a differential.

I'd say, "Now that's overkill", but I wanted to try and offer an explanation in different words... hopefully, it will help.

~Doozi