Originally Posted by
Jake Harsha
Because of this center differential, an AWD vehical can theoretically have three tires on dry pavement and still be stuck spinning the fourth. A part time 4WD transfer case (with open axle differentials) needs to lose traction on one tire on each axle before it becomes stuck. All other things being equal, a 4WD truck with the transfer case in 2WD will get better mileage than an AWD truck because it only suffers parasitic losses from a single axle differential instead of two. (This is especially true if the front axle has old school hub lock-outs, because then the front differential doesn't have to turn at all.)