The Office of Defects Investigation (ODI) has received one complaint alleging five transmission failures leading to loss of motive power across the fleet on model year 2016-2018 and 2021-2022 Chevrolet Express and GMC Savana cutaway vans equipped with 6L90 transmissions. The complaint alleges a loss of motive power when shifting into drive or reverse. The Subject Products can be used in a variety of applications including but not limited to ambulances and school buses. A loss of motive power in an ambulance could prevent the vehicle from being able to transport patients in time critical situations and in a school bus could result in students needing to be offloaded mid-route on the side of a roadway, putting them at risk. ODI contacted the manufacturer, General Motors, upon receipt of the complaint. General Motors identified two production runs of valve body separator plates that were incorrectly machined resulting in excessive wear to the plastic valve body check balls. This wear could lead to loss of motive power. General Motors stated that of the Subject Products produced, 89 vehicles were upfitted to ambulances and 1,961 were upfitted to school buses. Both the Micro BirdMBII and Thomas Built Buses Minotour buses were built on either the Chevrolet Express or GMC Savana chassis. ODI is opening this Preliminary Evaluation (PE) to evaluate the severity of the potential problem and to fully assess the potential safety-related problems. To review the ODI report cited in the Opening Resume ODI Report Identification Number document, go to NHTSA.gov.
