Abstract: Quality control inspection of a vehicle driving axle comprising a differential unit and two half-shafts, is effected by measuring the acceleration transmitted from the axle to a support structure as the axle is driven against a resisting torque. The transmitted acceleration is measured in terms of its three-mutually-orthogonal components using accelerometers which output electrical signals to a processing unit. The unit processes these signals to derive comparison parameters which are then compared with reference values, to identify certain faults which may be present in components of the differential unit.