DOUBLE SPLINED COUPLING FOR A TURBINE ENGINE

An assembly is provided for a turbine engine. This turbine engine assembly includes a turbine engine shaft, a gearbox and a coupler. The turbine engine shaft is configured to rotate about a rotational axis. The gearbox includes a gear configured to rotate about the rotational axis. The coupler is coupled to the turbine engine shaft by a coupler-shaft connection. The coupler-shaft connection is configured as or otherwise includes a crowned spline connection. The coupler is coupled to the gear by a coupler-gear connection. The coupler-gear connection is configured as or otherwise includes a crowned spline connection.