Claiming that towing with a T56 is no different than a NV4500 is the same as saying towing with a 1/2 pickup is the same as a 3500 dually. Sure your 1500 can pull that same weight, but can you stop it in a safe distance if required? The gears in the NV are taller and wider, the mainshaft is much larger diameter and the counter shaft matches the rest of the components as well as larger bearings. Those are the facts.