HELP!! 8mpg Dilemma - Pathetic 03 ram 2500 HD

[SavedByGrace]

Hi all - so im back trying to figure out what the hell is going on here. Currently 7.5-8mpg town driving normally. Highway i can get around 13.5 to 14 lightly loaded with 2 dirtbikes, which isnt the worst -

Traded this truck 5 years ago with a spun rod bearing. Replaced crank and bad rod, mic'd the whole block - everything was perfectly in spec after 100k miles. Put it all back together - New timing set / rings / bearings... (i rebuild chevys all day at my shop so im no fool around engines - but did i screw sth up?).. im losing my mind here.

Towing a 22ft boat is a joke, at 25 if i accel just about nothing happens.. the low end torque is non existent. WHAT THE HELL IS WRONG WITH THIS TRUCK!!! My buddy tows with his 04 chevy with 5.7 28ft boats no prob- blows my mind that this thing is such a joke. Im wondering if i messed up cam timing or some stupid error on my part?

Now the truck cam lifted with 2" in the rear. currently tires are 31" (285's), stock gearing is 3.73 i believe.

K&N cold air intake
Cleaned TB / replaced all sensors
NO CEL / NO CODES
Starts/drives just fine.
Confirmed good fuel PSI
New ign coils / Plugs new
New Cat converter / 0% backpressure (tested with inch lbs meter in o2 holes)
New HD torque converter (improved highway mpg by 2 from 8.8 to 11)

Bought a superchips and put in a tow tune - picked up an extra 2mpg highway(from 11 to 13.5/14) -


My co worker keeps telling me to do a gear change, maybe 4.10's or 4.3. We take this to the desert occasionally, i dont put alot of miles on it-

Ive been told if i had mucked up sth with timing i would get a code. Would a slipping trans give a code??? this thing has passed smog everytime..

Wits end here.

 

[tron67j]

Getting 4.10 or higher will kill MPG. I had a 03 2500 with 3.73 that I got around 19-23 mpg but it was 2wd extended cab 8' bed with stock wheels and tires. Your tires might be contributing to your problem a bit.

You could dyno the thing and get numbers. But before that, first check your boat trailer. Have you checked bearings and trueness of axle(s). Either one could result in you dragging more than towing the trailer, I suggest you clean and grease bearings, maybe even replace them if trailer is older. Check the wheels also for how straight they are aligned with the tongue.

You haven't mentioned rpm at various towing speeds, that might help shed some light. Also, have you checked out your truck's alignment and mechanics of drive system, could be dragging a brake or have a bad bearing there as well.

These are all things that can affect performance, but your rebuild specs are out of my league and someone else needs to take that.

 

[SavedByGrace]

truck rolls perfectly at a stop.. trailer tires and bearings are good, i checked them all.

This is how bad it is

2003 ram 5.7 what is wrong with this thing

Terrible mileage. No towing power. New cat, new HD TC. Reman shortblock 10k miles back. Engine was 100% in spec. Not a single issue. Verified fuel pressure, ...

www.youtube.com

 

[06 Dodge]

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[HemiLonestar]

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REALLY curious as to what this was before edit lol.

 

[SavedByGrace]

yeah thanks tron.. its like that with the trailer or not- just an absolute ****..

 

[culprit65]

Getting 4.10 or higher will kill MPG. I had a 03 2500 with 3.73 that I got around 19-23 mpg but it was 2wd extended cab 8' bed with stock wheels and tires. Your tires might be contributing to your problem a bit.

You could dyno the thing and get numbers. But before that, first check your boat trailer. Have you checked bearings and trueness of axle(s). Either one could result in you dragging more than towing the trailer, I suggest you clean and grease bearings, maybe even replace them if trailer is older. Check the wheels also for how straight they are aligned with the tongue.

You haven't mentioned rpm at various towing speeds, that might help shed some light. Also, have you checked out your truck's alignment and mechanics of drive system, could be dragging a brake or have a bad bearing there as well.

These are all things that can affect performance, but your rebuild specs are out of my league and someone else needs to take that.

I had vacuum leak on my 06 2500 no EGR where the tube would go on the intake it’s like a thimble with a little blue gasket on it. My mileage went from about 12 to 13 down the 7.4.

 

[culprit65]

I had vacuum leak on my 06 2500 no EGR where the tube would go on the intake it’s like a thimble with a little blue gasket on it. My mileage went from about 12 to 13 down the 7.4.

 

[culprit65]

I had same problem on my 06 mega cab mileage went from almost 14 to 7.6mpg