Bigdaddy, in reply to your question, to the best of my knowledge, Ram doesn't make a 4.56 gear for the 2500 HD. The 2013 and earlier PowerWagons had the 4.56 but have also went to the 4.10 gears. (They have a locker diff so gears wont interchange) After more than a few discussions with Ram, I got approval to re gear using the 4.56 that I believe are a Yukon gear. (listed as a GM gear) As my dealer was instrumental in my ability to keep the 5/100000 warranty on everything but the gear sets, I had them do the work. Was more expensive but having and keeping good relations with the dealer I felt was worth the cost. For the record, they did an excellent job and no problems after about 15k of driving and towing. As for empty mileage, probably lost a couple if driving elevations were near sea level. Here in CO, with elevations starting at about 6000, probably lost nothing and maybe better than stock for city driving. Definitely changed the power characteristics. More like a truck and still tacks only 2300 rpm at 80 in 6th. Truth, if available, would consider something around the 4.88 range knowing what I know now. But that's just my thoughts and likes entirely.