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Fin pitch, shape, length, and fin count all influence stall speed. Fin pitch is the only variable that can be changed without physically modifying the stator fins, which is precisely how the GM system works. As with most torque converters, a standard TH400 stator (left) has fins situated at a fixed angle. Conversely, a variable-pitch stator has hinged fins that can open and close to change the converter’s stall speed.