Method for manufacturing a gear

A method for manufacturing a gear, comprising:

• providing a rim gear, a hub and a core wherein the core is annular and has a core forging temperature below a hot hardness temperature of the rim gear and the hub;
• rotating, about an axis, the rim gear and the hub relative to the core, the rim gear and the hub in contact with the core to generate friction heat to raise an interface temperature of the core to the core forging temperature without melting the core;
• driving the hub into the core to upset a first portion of the core into an outer annular groove defined in a first faying surface of the hub, wherein, prior to driving the hub into the core, the core has a core inner diameter smaller than a hub outer diameter;
• and
• driving the rim gear over the core to upset a second portion of the core into an inner annular groove defined in a second faying surface of the rim gear, wherein, prior to driving the rim gear over the core, the core has a core outer diameter larger than a rim gear inner diameter.