Chevrolet Express and GMC Savana transmission software causes wheel lockup critical
The computer that controls the transmission was loaded with the wrong software. Because of that, the van can shift harshly, lose power, slow down on its own, suddenly lock up the rear wheels, or move in a direction you did not select. Locking rear wheels or unexpected movement can make you lose control and crash. Dealers will reload the transmission control module with the correct software, free of charge, which fixes the problem.