Has anyone tried auxiliary transmissions? I was looking into it and thought it'd be great for millage and power handeling. I first looked into it for towing power, but found these guys, Gear Vendors and some of the stuff they do.
Is there any imput out there for these things.

 

I've only heard of them used on big rigs, to give more gear ratio flexibility for hauling heavy loads in steep country. I'm not sure how they would increase gas mileage.

 

The extra overdrive would help in millage. At highway speed when in Double Overdrive, the engine would use fewer RPMs for the same speed stock. Just wonder how well it integrates with the automatic shifting, and how much power it can handle. They rate the efficiency (on this one) @ 1hp per 400hp.