This is my 01 Ram, Cummins HO, NV5600, changed gearing to 3.73 instead of 4.11, pulling a heavy load. Pulled the WW with this truck on same trip route, 4900 miles. Pulled the same trailer up the same grade from LV to Baker, at 55 mph in 5th gear. Fuel mileage for the same trip was exactly the same to a tenth of a MPG. I really want a gear vendor unit. Mostly I drive with a Madds Smarty programed to economy mode. I use the firs power setting for towing. It's much smoother than the stock program.