If I remember right, back in the 60's Buick used a two pitch converter in their 2 speed auto. It had an electric (I think) switch that changed the stall on the converter. Used for passing gear at highway speed, without kicking all the way down to first. It's been a long time, so my memory could be a little off, but that's what I recall. Also used by some modified by connecting the lead to the brake lights to allow a higher stall at a full stop, but switch it back as soon as you let off the brake.