Abstract: A drive transfer gear assembly for a four-wheel drive truck tractor. The tractor includes a front drive steer axle assembly, a rear drive axle assembly containing the drive transfer gear assembly, and a prime mover drivingly connected to the front and rear drive mechanisms by the drive transfer gear assembly. The front axle assembly includes a rigid axle housing having end sections and a drop center section containing a differential gear set with output gears drivingly connected to wheels pivotally journaled at the outboard ends of the rigid axle housing. The rear axle assembly includes a differential gear set with output gears drivingly connected to the rear wheels, and a drive transfer gear assembly positioned forwardly of the differential gear set.