GM 6L90 Transmission Problems Investigated

Chevrolet Express and GMC Savana cutaway van 6L90 transmissions allegedly failed.

GM 6L90 Transmission Problems Investigated

Posted in Investigations

— GM 6L90 transmission problems have caused the National Highway Traffic Safety Administration to open an investigation based on five alleged transmission failures.

All the General Motors 6L90 transmission failures occurred in 2016-2018 and 2021-2022 Chevrolet Express and GMC Savana cutaway vans.

Specifically, the complaints allege the vehicles lost motive power when shifting the 6L90 transmissions into DRIVE or REVERSE.

NHTSA is concerned because GM vans equipped with 6L90 transmissions can be used for an ambulance or school bus. One of the last things an ambulance needs is to suffer a transmission failure, preventing the transport of patients.

And regarding a small school bus, students could be stranded and offloaded on the side of the dangerous road.

GM told NHTSA at least 89 vehicles were upfitted to ambulances and 1,961 were upfitted to school buses, and all are equipped with 6L90 transmissions.

Safety regulators have already contacted GM about the 6L90 transmission problems, and the automaker has already found problems with the valve body separator plates.

GM told NHTSA about two production runs of valve body separator plates that were incorrectly machined. This can cause the plastic valve body check balls to experience excessive wear and cause a loss of motive power.

Safety regulators opened the investigation to determine the severity of the 6L90 transmission problems. will update our website with results of the GM 6L90 transmission failure investigation.