Have a 2005 Dodge 3500 dually with a 5.9L. Just put new pistons, rings, bearings, etc in it about 5000 miles ago. Tranny is stock as far as I know. Cold Air and 4 inch stainless exhaust to 6" tip. My question is how much of a difference would a tuner make to the truck? Could I run an economy tune (50-70hp) and get better mileage? How is that even possible? Always thought more HP more fuel?

Any feedback would be greatly appreciated for this newbie

David

 

The right tuned would certainly help your fuel mileage and drivability in some cases with better throttle response time

 

As a newbie not sure what kind of "upgrade" the rebuilt motor can take? Do you think the tow/economy would work ok?

 

that is not always ture. guys have seen worse, the same and better fuel mileage with a tuner. many do get better mileage, but better mileage is not certain with a tuner.
your engine is already broke in since you have put 5k miles on it. assuming you have an auto, your tranny will be your weak point. i have a manual so i dont know much about autos other then you should upgrade parts or even get it built depending on what kinda power you are gonna add to it. i think you can add some power with a stock tranny, but how much? i dont know.

 

Tune it- since you have an 05 smarty is going to be best probably. Be sure that you run gauges to keep an eye on things especially since you just had that work done. Trans is the weak point but as long as you aren't drag racing and doing boosted launches you will be fine with the trans and mild tune. I used to run EJWA with setting 4/5 helped with hwy mpg and 2/3 helped with city. Every truck responds different to each tune even though it's the same programming so one size does not fit all! Just beware of the HP bug once you get some pep in that Cummins it's a dangerous thing