Abstract: Transfer gearing for converting a vehicle with a single power-driven axle to four-wheel-drive is housed partially within the vehicle's gearbox. The transfer gearing comprises a train of gears on vertically spaced shafts, the lowermost shaft having a coupling flange adapted to be driveably connected by a cardan shaft to an auxiliary power-driven axle, and the uppermost shaft being disengageably connectible by clutch means to the output shaft of the vehicle's gearbox. The clutch means comprise a dog clutch sleeve slideable axially by a selector fork operated manually by means including an arm pivotally mounted externally upon the vehicle's gearbox.