A method for manufacturing a ring gear/differential case assembly includes attaching a ring gear to a differential case. The ring gear and the differential case are fabricated of materials having differing properties. The attaching includes placing a first portion of the ring gear in intimate contact with a first portion of the differential case whereby a predetermined gap is defined between another portion of the ring gear and another portion of the differential case. The ring gear first portion is attached to the differential case first portion by a friction welding process. The predetermined gap defines an outflow channel for receiving an overflow material created by an upset forging step of the friction welding process. Differential assemblies and vehicles including such are described.