Hello, I was just wondering if there is anyone that has completed a rear end gear swap on a 2003 2500 two wheel drive with automatic. I have this truck and it came with 3.73 gear ratio in the rear. I was told by some friends that I could drop to a 3.08 or 3.42 gear ratio and would bring my mileage up 4 to 5 miles per gallon. I do not pull anything more then my four wheeler on a sixteen foot flat bed. I drive on the highway going offshore and back and fourth to town which is 20 something miles away. I run at 65 to 67 on highway and I get 24.3 to 25.2 miles per gallon. Set me straight on this once and for all. Thank you

 

Tell your friends to lay off the crack. There's no way you'll gain that mileage with a gear swap.

 

Maybe just maybe 1 mpg going to 3.42. Leave it alone.Its the best mileage truck out there the way it is.Drive slower will net you more mpg at no extra cost.

 

thank you for the information I thought they were full of crap

 

A slightly taller tire will help some at no additinal cost at retire time. Slowing down 5 MPH will give biggest bang for no bucks. On a 20 mile drive it increases driving time by two minutes at most. Gear ratio change will never be recouped in most truck lifetimes.

 

My 03 (4x4) with 4:10s is still getting not-so-great mileage. I've had it in twice, the first time they replaced all 6 injectors. The second time they reprogrammed the ECU with the latest flash for the 03 5.9 HO. I think I'm being nice to say I'm getting 20 on the highway at ~60mph (2K rpm).

Any other ideas, mileage gurus?

I did make the mistake of putting 265 wide tires (highway, forget the height but it's the stock height) on the truck so I think I have a little more rolling resistance because those are wider than stock... but still... Always looking for more ideas to try...

PS - Yes I did replace the fuel filter recently. Air is practically new too.