I have an '03 F250 SCLB with a 6.8 and 3.73 gears. It just turned over 100k and has slightly oversize tires (275/65R18). I am towing an ultralight 19' trailer that weighs only 3500lb dry. I had the tranny rebuilt 10k ago because of a bad TC seal that leaked, and had a shift kit installed to firm up the shifts. It runs just fine except for an annoying drone at 2000 rpm and up. It has the original y-pipe. I've been to Mike's site and checked out the graphs on what his tunes and a new y-pipe can do for the performance, but the results on the graph aren't that convincing to me. Here's the issue: when I'm pulling a grade above 6% it's an absolute dog; it doesn't matter what I do with the gas pedal, it just won't pick up speed unless I downshift to 2nd gear and scream up the hill at 3500rpm, which kills the fuel economy and drives me insane with the noise. I'm hesitant to re-gear to 4:56s to the tune of almost $2k and buy Mike's Tunes, and add new headers and a Y-Pipe to boot. I want to be able to tow at least 10k without cursing every time I have to climb a decent grade. I'm just returning from a trip to Colorado and NM, and climbing those 11k grades was beyond disappointing, to say the least, especially since the trailer is so light. Any advice? I'm almost ready to bag it and go to a diesel..would spending at least another $3k on gears, etc. really make that much difference?

 

To answer the question at the end of your post, YES!
My EX has the same 2 valve motor and 4R100 trans that your '03 has and the Ex might be little bit heavier. I'm sure it outweighs yours with 5 adult sized teens and all of their gear along with my wife and I aboard, that is the passenger load on some of our towing trips.
Our Ex started with factory 3.73 and then we started pulling a 9.5k 31' toyhauler, it wasn't much fun on any kind of grade, a lot of downshifting, revving and crappy MPGs. On a couple of trips from Philly to/from NC, SC and GA we were seeing from 6.5 to 7.5 MPG and I wasn't happy with how gutless it felt pulling any sort of hill. During this time period I was running a set of 275/65R18Es that were 32" tall, almost the same as the EX's factory 31.5 tires.
I then found a set of axle housings already setup with 4.88s for a decent price, so they got swapped in. WOW! Totally different truck with these gears. Pulled the same trailer on a trip to/from VA, WV, TN and KY, plenty of decent mountain pulls in the Blue Ridge and Smokey Mountains, nothing quite as big as the Rockies but big hills for we East coasters! It just ate the hills up, much much less downshifting and all around better performance while towing. And it felt kind of like a hotrod running solo.
Before we made a repeat trip over the same route as we had done with the stock setup I also installed a set of Banks headers. With the Banks headers and the 4.88 gears we made the same trip to GA as before, same route, same trailer, same weight and same speed (60-63ish MPH) and we got 9.0 MPG! The trans didn't drop out of OD the entire highway portion of that trip, fairly flat drive along I-95 but in the past the rolling hills in MD and VA would have it dropping down frequently. This was the combo on that trip.


Since then I have added an SCT tuner from 5 Star Tuning and have played around a little to find what works best for my style of driving/towing, I'm not racing anyone and am willing to give up a little speed on a hill to hold OD and keep the MPGs up. I have found that the 87 Octane Performance tune is a pretty good match with how I tow. My EX now has 35" tires so my effective ratio is now 4.39. And we have traded up to a new 11k 41' Travel Trailer. On a trip in April from Philly to Blacksburg VA to Bedford PA then back home again (870 towing miles) with a lot of miles on I-81 up and down the Blue Ridge Mountains we again saw 9.0 MPG. (All mileage was based off of my GPS that matched up with Google's route miles due to my odometer being off with the taller tires). It still holds OD very well and only drops down when really needed and has plenty of usable power in the 2000-2200 RPM range that it lives in at 60-65 MPH. The tuner makes a huge improvement in the trans operation and I feel that it adds a nice seat of the pants engine power bump. I am super happy with the gear, tire, header, tuner combination that we now have, I think my V-10 is doing everything I could ask of it.
This is the new combo.

 

Only 3500rpms? These V10s love to rev. The very last thing I am worried about is mpg. 1 mpg difference on a 400 mile trip is only $24 in gas. For sure do the exhaust mod(headers or Y mod) This will help it breathe at those rpms. 4.30 gears would be great too but lots of $$.

 

At 3,500 rpm the engine is not "screaming". If you are not going to let the engine get close to the peaks of the torque and horespower curve then you get what you get. Trade the truck in on a 7.3l or 5.9l cummins if you can't handle revving over 3,000 rpm.

 

You think the v10 revs high try towing a 7000lb 27ft travel trailer with the current 5.0l and 3.55 gears. I did that last year and I was done. I traded it for a 05 f250 v10 4.10 gears cc 4x4. This thing tows like a dream. Granted it was not the f150s fault it's just the nature of the 5.0. I will say this I do miss the 5.0's get up and go. Those things rip but the v10 just had that low end grunt that the 5.0 lacked. Nothing wrong to let it sing a little that's what they're made for. What I like about the v10 is I never saw much over 3k rpm during moderate acceleration towing camper for first time last weekend. I love mine so far. My brother has had 3 of them and has loved everyone of them. His current is a 3v like mine and absolutely loves it. Just regear your truck. It's still cheaper than a diesel.

 

Wow, thanks, Tom! That's just the kind of reply I was looking for. I don't mind spending the coin to get what I need; I just want it to do the job for me after it's all said and done. Thanks again..

 

DKF, when it's running at 3500 RPM it's way over the torque curve peak at 2500 RPM. My fuel economy shrank by over 30% when I climbed out of Silver City, NM at that RPM, and yes, it did sound like it was screaming to me..I don't care that it may top out 1000 RPM higher. The optimum RPM for fuel economy is at about 2500 RPM or less according to over 4k of travel over the past 5 months. I do care about the mileage, especially over those distances. Can't handle it? What an asinine, snarky comment. Try to use some class when you reply..

 

An 03' is a PI version makes peak torque @ 3250rpm and peak hp @ 4250rpm. At 3500 rpm that is good place to be when pulling. You have the wrong vehicle for mpg and high engine loads at lower rpms suck for mpg too. Then you compound the problem and reduce mpg and hurt the final drive ratio(increased rolling resistance and engine load) by upping the tire size. It is what it is. The tuner won't help your towing mpg and gears are unlikey to make a big mpg gain depending on what mph you tow at and load. The gears will help big time with torque to the ground and that is what you want when pulling a load and the tuner will bring the A/F ratio where it should be, allow WOT fuel enrichment, add some power, take a lot of the lag out and make the trans shift better. But you still are not getting near the performance out of the truck if you don't want to run it over 3k rpm. This is a N/A gas engine not a forced induction diesel. If mpg is such a concern best to just buy a Prius and stay at a hotel. I tell it as it is, some people don't like that and I don't care.

The SPD y-pipe is pretty annoying with the stock manifolds due to the exhaust flutter. My dad has it on his 03'. The best bet is to go with a set of headers which come with a new y-pipe, I went hat route on mine. No flutter and more power from the headers/y-pipe, just some extra header noise from the thinner tubes.

 

You can't lug overhead cam motors & expect them to perform. They are built for RPMs. I agree gas mileage is found in small cars, not working trucks.

 

These are some of the exact reasons why I bailed from the V10 to a 7.3L. No matter what anyone says, the V10 really isn't much of a heavy pulling motor, even compared to a 460 in some aspects. I was lucky enough to be able to buy a KB supercharger when they were available and had installed that, along with custom tunes from diablosport, 4.56 gearing with 285 tires, headers and 3" dual exhaust pipe with flowmaster mufflers; just to have it return mediocre towing performance and far worse MPG. ( I anticipated less mpg, but not 5mpg unloaded....) I once took a trip from VA to FL and spent $1100 on fuel.... Never again did I go camping using that tow vehicle.

In the end, it struggled too much towing a 8k TT, and when I moved up to a 11k TT with a much larger frontal area, the truck proved to be inadequate. It didn't matter if it was screaming, lugging or whatever (which it seemed was either one or the other, it was never happy), I was tired of 25 MPH climbs up 4% grades and 2-3mpg jaunts to the rv parks.... I happily sold it for $8k and used that money to buy a one owner '95 F250 7.3 PSD 4x4 for $4k, made some transmission updates and other upgrades all myself with $2k and have a much more capable tow rig that returns 12+ mpg while towing and 18+ mpg unloaded. Included in that $2K upgrade price was a suncoast rebuild with triple disk converter, a tuner with six custom tunes, 4" exhaust that I fabricated for under $100 and a full air suspension, in addition to the modifications made in my signature.

Really, the only things I miss about the v10 truck was how quiet it was, the inability of the engine to produce enough power to damage the transmission and the comfort of the Super Duty Crew Cab body. Other than that, the new truck has been a blessing in disguise. It's had a couple of hiccups, don't get me wrong, but nothing to the tune of the $3k supercharger, $1500 exhaust and $800 worth of gearing upgrades that didn't do a whole lot for an engine that can't breathe. I can assure you, the V10 would have been a much better engine had they put some actual thought into the cylinder head design. The exhaust ports are way too small to be efficient and the intake ports look like they were sized for the old Bronco II 2.9.

FYI; I'm seriously not bashing the V10. I owned it from 2001 to 2012 and put 186k miles on it. In the end, I just became sick with the operating costs. When I bought it, gas was $1.08/gal., I could put up with the low mpg then and with the lighter camper in a flat area such as southern AZ, it was ok. Later, when a move to the east coast came and a new RV was purchased, it just seemed to be too much overall. I mean, just to go the 180 miles to VA Beach costs $250 in fuel, it became a problem. So yes, I think that efficiency should be your first concern when considering a work/tow vehicle. Also, cost effectiveness as a close second. I used both of these as basis for my purchase of an 19 year old diesel.

 

WOW, that is a huge trailer... you would have a hard time fitting just the trailer into some state parks here in OR.

 

I don't have this truck anymore but this is what I pulled with it, the only add on it had was a Banks Cat Back exhaust system. It was a 2000 V10 with 4.30 gears 215/85/16 tires and it did a good job pulling our 16K trailer. The photo was taken at the top of Berthoud Pass CO,the sign says 11307 feet.

Denny
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Thor, thank you! Over this 4k trip I've put up with really crappy power pulling the 3500 lb trailer up any decent grade, and only got 8.5 MPG on average. I'm dumping this thing and going diesel. I don't want to invest at least $3k and end up with a dog when I upgrade to a 15k trailer. Anybody want a low-mileage 2003 F250 SCLB? It runs great..

 

It's all about gearing and "torque to the ground" ... Over the years here at FTE, I've posted quite a few times about engine RPM, tranny and rear-gear torque multiplication, and tire size.

The quick fix is, yes, get a diesel. It might be cheaper (or just a lot easier) to do, then to massage your V10 into the towing machine it can be. With 3.73's and larger tires, you started out on the crappy-end of the stick.

Just remember, there are trade-offs when it comes to mileage, and power. Many here, at least in years past when the 7.3L was a viable option new, found that the "diesel is better" motto was not always true. Sometimes it is.

If it works out for you, more power to you

 

I had a 1999 V-10 pulling a fifth wheel that was much heavier than your trailer and much taller to boot. Once I changed the rear end from 3.73 to 4.30 (stock tires) it towed fine. But you've got to let it spin, or you're wasting your time.

I currently have a 2010 V-10 (4.30) pulling an even larger fifth wheel, weighing about 15,000 pounds. I've pulled a great many 6% - 8% grades with no issues. But again, you're going to be spinning going up those grades, at over 4000 rpm. The engine will do that all day long. Doesn't heat up, doesn't slow down, does use gas. But you make it up going down the other side, right...

If you want an engine that will pull anything and not exceed 2500 rpm, you've absolutely got the wrong truck. But the truck you have should pull your trailer easily. Just let it run.