System: steering; unknown type; shaft sector.vehicle description: medium duty truck, school bus chassis, and commercialchassis.note: if your vehicle IS presented to an authorized dealer on an agreed upon service date and the remedy IS not provided within a reasonable time and free of charge or the remedy does not correct the defect or noncompliance, please contact chevrolet service center at 1-800-222-1020 or GMC service center at1-313-456-4547. Also, contact the national highway traffic administration's auto safety hotline at 1-800-424-9393.