I have a 2003 Heavy Duty F250 FX4 V10 and am extremely dissapointed by its lack of power and torque when towing. I pull a 7000lb toy hauler and have to downshift all the way to 1st gear to get moving on a 5 to 8% grade. I surely never come up to speed and have to race the engine to make any headway.
I've spoken to other owners and they pull heavier trailers at better speeds and say they still have power to spare. My gas mileage drops from 10 to 7 when towing, which I know is the curse of this monster, but I refuse to believe this 6.8 Liter engine can't handle this trialer with ease.

The only improvement made to this truck has been a K&N air intake. I can't help but think the tranny or rear end are not properly matched to this engine and that the RPM shifting ratios are not in sync. I believe I have the 3:16 rear. Can anyone tell me what to look for to make this truck act like the big beast I thought I was buying?

 

I have a 2004 v10 and it pulls my 16 foot carson like there is nothing behind it my trailer fully loaded is probably around 6500Lbs.. I have 33's and 4.30 gears so maybe this helps. When you tow are you turning off the overdrive? Also are you using a weight distributing hitch? Also I assume you would have 3.73s not 3.16s which should be fine to tow that trailer. The 7000lbs is that fully loaded with gear toys and water?

 

I don't know the exact weight, it is a 21ft Ragen and I'd say loaded is maybe closer to 8300lbs. I do use a weight distributing hitch and drive with the OD off. Yes, 3:73 sounds right.

 

Not sure what the problem could be. I am coming into a V10 from towing with my 1/2 ton 4.8 silverado and it is night and day for my trailer. You have quite a bit more weight than I am carring so maybe that is coming into play?

How many miles on the truck?

Maybe your expectations are higher than mine LOL.

 

First, Welcome to FTE!

Those 3.73's aren't doing you any favors. Those gears are fine for commuting / light duty towing, but if you wanna move weight with the V10 you need to run the 4.30's. You're talking about moving 7,000 lbs+ of truck, plus that 8,000 lbs+ of trailer.

The V10 likes to rev and the torque curve gets flat around 2200 RPM. Running on the highway and around 65 to 70 MPH, you need to be in the 2250 - 2500 RPM range to put the V10 in it's sweet spot.

Don't be afraid of a little RPM in that puppy, it's built to handle 6K RPM, bu the rev limiter kicks in around 5400, so you have room to spare.

And yes 7 MPG with that weight is normal.

Forget the programmers, chips, intakes, exhaust, whatever.....if you want to improve that towing performace, the single biggest improvement you can make is to change the gear set. Get the 4.30's installed and you'll be a much happier camper.

BFR

 

i have to dito above for what you are doing that set of 373's are killing you. regear it to 430's and don't worry about tuners and other junk unless you are going to go up to a supercharger kit as that is about it. other then haveing the flow resricting ypipe modified by haveing a shop cut out the resricker with a flowmaster or stans headers ypipe . part number flo y 250300 from summit racing price is about 40 dollars plus install

 

If you got this truck used, or even if you got it brand new, it might be time to do:

1) Fuel filter - mine was pretty clogged by 20K miles. BIG difference in upper-end performance after changing it.
2) Clean the MAF - with a K&N (and even without it) you might have a coating of crud/oil on the MAF wires. This WILL result in a lean mix because the computer doesn't know how much air is getting into the motor. I use paper filters on my V10, and with only 24K miles on it, I've already cleaned it at 20K - again, BIG DIFFERENCE. And the wires WERE dirty on one side.
3) Plugs - at 3-4 years old, I would do them just to clean and anti-sieze the threads. I did mine at 21K or so, and another BIG difference. Put on new boots too.

If you have the 3.73's that WILL kill you, but you shouldn't have to be in 1st gear pulling up a grade.

I'd certainly do a "tune up" as outlined above and see if that helps ... and if not, something's wrong. Report back, we'll keep working on this

 

Do you have oversized tires?

 

Thinking the same as you Big Orn. A 03 2v V10 with 3.73s should not struggle with that load. I pulled significantly heavier and up steeper grades with my 01 2v V10 3.37 combo. Just had to be down in 2nd at 4800rpm but she still have pedal and never really felt like a dog.

That truck should have 265x70x16 31.2 inch tires on it. Not much data in the post, sounds like bought used. My guess is lifted and 33 or 35s are on it.

Wallboyz set me and Big Orn straight.

Welcome to FTE and the BSEG forum

Tell us a lot more about your truck, and what kinds of terrain you are in... Curious that you say, when towing it drops from 10MPG down to 7MPG. Do you mean you only get 10MPG around town and out on the highway when empty?

 

First thing I would change is the fuel filter. My 03 started to have problems like you say you are having. I would pull out on the road just the truck no trailer it would hardly run have to give it half throttle just to get moving and was having a mild loss of MPG.

 

I appreciate all the feedback from everyone, thanx.

Yes, I bought this truck used from a freind that used it for commuting to his salvage yard. It was only used for towing a 15 ft carson box trailer to the desert a few times and was not used as a work truck to haul loads. I'm under the impression he took good care and changed the oil every 3000 miles, yet I have no clue about his other maintenance habits. I haven't much info from him nor can I reach him for further help. I am in San Diego so it is equipped with Smog control.

I've only had the truck for 4 months and have yet to do my own maintenance but the fuel filter sound like the place to start. It does have the stock size BFG 265/75/16 tires and is not lifted beyond the standard heavy duty FX4 package. It also is a long bed if that makes any difference. I have gotten 12 mpg highway when I drive under 2K RPM and long distance without a load but my average is 10 mpg.

I don't have any manuals for the truck nor the original sticker. I have looked at the rear diff and it has a 12 bolt pattern and can not verify the diif. size, any clues on how to know for sure? There is a green sticker on the axle itself with the number V425C.

 

ok for a shop manual thats a peice of cake .
you have to use IE but go into www.motorcraft.com at the very top click on the area that says technical. resourses near dead center at the left colum is owner guides bring up your truck they have all 5 editions listed . down load and save where you can find it..

price is free

 

The tech manual will also tell you how to interpret the door codes, which in turn will tell you the axle.

 

hope it still has the tag under the bolt on the cover makes it a tad easier.

 

I reviewed several of the tech manuals and found the door tag decoder label but I don't see a cross reference for what the numbers and figures mean. The tag is still on the bolt but I'll have to wait for daylight to check it out.