So I have a buddy with an 04 singlecab 3500 4x4. It has run fine up unlit this past weekend he went to the coast to get 40' gooseneck load of round bales. well while he was way overloaded he only got 3.9 mpg, he said that the whole time his truck was havin hell runnin in 5th at 3 grand. He was following another guy with a 04 3500 four door 4x4 with the same weight and he got like 12. So he took it to the dealer and they told him that they reflashed the computer and now its back runnin like a top. Has anyone had problems like this before? and I fixin to get an 03 and was wondering if it has ever happend to and 03?

 

I pulled my 25' trailer with my 04 3500 from the KY/WV line to KY/IN line today hauling a 2005 chevy 1500 and I was getting about 11.9MPG running 70 on I-64 up and down the hills, then on the way back W/empty trailer 70-75 I got 14.5MPG.
I know that my MPG went up after my liftpump went out and they put the retro kit in. I'm gussing they flashed my computer when it was there because I had the high idle activated while it was there. So one of the 2 helped.
I don't know about the 03s

 

There was aTSB Technical Service Bulletin to reflash the 03 ECM which my truck fell under. I believe it was for cruise control problems. I don't believe it had any thing to do with fuel economy. You can check the following website for TSB's http://dodgeram.info/tsb/2003-index.htm which is sponsored by Geno's Garage www.genosgarage.com. If the truck has been reflashed there should be a sticker somewhere under the hood. Mine's on the upper support in front of the radiator. If there is any question take the VIN to a Dodge dealer and he can tell you whether that vehicle needs to be reflashed and if it has been done.