Rear End gearing

[RGH43]

I have "07 3500 4X4 Dually automatic that has a 4:10 gearing and was thinking of changing to a 3:73 or 3:56 or similar. Now I get at best about 14mpg empty so I'm trying to improve my mileage, what mileage could I expect by doing this. Does the cost exceed the savings. Since this is a 4X4 I would have to do both or remove the front drive line since I never have used the front wheel drive. #2. If & when I start towing again I would be hauling a 5th Wheel @ about 12K, is changing the gearing a dumb idea or not?

 

[Motorhead]

If you are planning to tow a 12k fifth wheel then I would definitely keep what you have for gearing, especially with an automatic trans. You might try a Smarty jr to increase the fuel timing which might help a little bit. Having a set of un-locking front hubs can help a bit. Just remember....If that truck was a gasser, it would only be getting 8mpg

 

[mfurrh55]

373 gears will tow 12k fine and your fuel mileage should increase running empty

 

[cerberusiam]

The 4.10's will handle the load better and likely yield better efficiency. A dually 4x4 just is not a good DD vehicle, no matter the gears. A good tune, a few hard part changes, and taller tires will help that but it will always be challenged, no matter the gearing.