I have the GearVender unit and auto tranny. It works good on the freeway (1500-1600 rpms at 75-80mph). I think you need a manual to get the full potential. The 1600 rpms at cruising speed is very quiet and really reduces the wear on the engine. It has tons of torque at 1600 rpms and only down shifts on really step grade. I use it in town in the tow/haul mode. My convertor locks up at 28mph and I shift into the GearVender overdrive at 40mph, rpms drop from 1800 to 1200. Otherwise I would have to wait to 50mph to shift into the stock overdrive and rpms are 2000 to 2100. I've gained a 1 to 1.5 mpg in doing so.
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