Hey guys,

I'm going to ramble a bit about my towing experience this weekend and I'm looking for input from seasoned vets that tow regularly with their 6.0.

Intro- I've owned my truck since new- 2004 F-250 CC 4x4, but until now have only towed very occasionally and usually rather light stuff (motorcycle trailers, the occasional boat, etc.). I just purchased a new 20 foot travel trailer for hunting and fun use, so only now after owning the truck for 9 years am I starting to use it how it was intended.

Truck specs- Truck has 110,000 miles on it and has an 8" lift and 37" tires with 3.73 gears in it (I've been contemplating a gear swap and this is one of my questions). I've got the complete Bulletproof Diesel setup (remote oil cooler, upgraded EGR cooler (EGR function disabled via SCT and Gearhead Matt's tune), remote filtration, etc. I run Matt's SRL tune.

The load- The trailer in question weighs about 5,000 pounds with full water tanks. In addition to some camping gear, I also had my Yamaha Grizzly 700 atv in the bed which weighs about 600 pounds. The trailer is fairly tall and the front of it is about as un-aerodynamic as it can be.

The ramblings on my experience this weekend- In short, I was a little surprised at how hard the truck seemed to work to pull this thing. What I'm basically after here is some re-affirmation of my suspicions surrounding my axle ratio as it relates to the 37's, as well as some input from people who tow as to the boost I was seeing, etc.

First off, I DID tow with Matt's SRL tune on the truck because I figured the load was relatively light. I know that tune affects torque converter lock-up among other things, and in hindsight I'm thinking I should have swapped in one of the basic SCT tow tunes. That is one thing I want to try out.

In short, I feel that the truck seemed to labor to get up to speed and the boost I was seeing was, in my opinion, excessive. I was also disappointed in the fuel economy- about 10 MPG. I made specific notations that at 55 MPH I was at 1400 RPMs and sitting around 10 PSI of boost. When running at 75 MPH I was at about 1850 to 1900 RPMs and depending on where I was in the throttle, boost was 17-22 PSI. All these figures came from my Edge Insight, with the exception of the boost which is from my Auto Meter analog gauge. Are these RPMs too low? Seems like it to me???

Hitting hills on the interstate required significant throttle changes to try and maintain speed and it seemed like the truck did not want to come out of 5th gear and downshift unless I REALLY got into the throttle. If I did that, it was harsh downshift that I didn't like and the boost went way up. My overall impression on this is that the truck was bogging and that's why the boost was always up there, as the engine was trying to overcome the low RPMs and the wind drag of the trailer. I must say that a couple of times I got up to 80 MPH and it SEEMED like the faster I went the easier things got for the truck- maybe it was just me but things seemed much easier at 80 versus 60 or 65. When I ran that fast I did see coolant and oil temps get around 215 though.

I just can't see this trailer causing this much strain on the truck- it's not that heavy and I read of many people pulling much heavier loads. Is my under geared axle ratio that I've lived with for years because of the big tires finally making a big dent in the truck's performance? Without a trailer hooked up, the truck has been decent around town and on the highway although it does seem to unlock the converter and downshift on hills on the highway (which I hear is common for lifted trucks with the stock axle ratios). For this reason, I've been thinking about installing 4.30s after reading about others here saying it made it a whole new truck. Could everything I am describing be mainly attributable to the truck being under-geared?

Now- the tune. Could the tune be keeping the torque converter locked up and not allowing things to be "loose enough" to allow the engine to power through rises in the road, etc.? It acts like a manual transmission car that is in 5th gear at too low a speed.

The boost- this can't be right what I reported above. In my opinion, I shouldn't be sucking fuel like this and I can't imagine these trucks are meant to stay in the boost all the time when towing. Here is where I would like some numbers from some of you that are towing and taking a close look at the numbers.

I'm sure I think of more to add, but this should be enough to get the discussion started. I'm hoping you guys can help me shed light on this. If it's the axle ratio, I am willing to do a gear change. I've been thinking that my around town MPG would improve anyways since the truck is working harder to get things rolling. Let me know what you think, and THANKS!

 

Pretty sure the 8" lift and 37" tires aren't helping you out at all. I would highly recommend switching to the tow tune and trying it again as the shift points are greatly affected as well as throttle input required to downshift.

 

I think your tires and 3.73 gears are not helping either. I tow a 10,000 lbs 5er with my 07 and it pulls very nicely. So well in fact that the first time I towed with it going across North Dakota I did not realize the 35 mph+ head wind I had until I stoped. I avg 11.9 mpg towing 5er to Yellowstone and back (2300 miles @ 67-72mph).

I have towed my 20' flat car trailer with a 85 F350 on it and snow plow (10,000 lbs) with the SRL tune because my SCT tuner was broke. I took it very easy and it seemed like I had all the power I needed and more. It played wityh that load.

I will let someone with more knowledge chime in, but 5,000 lbs is not much load for these trucks. My 02 V10 F350 would play with 5,000lbs and that was not even close to my 6.0 dsl.

 

Lift and tires are definitely working against you. I definitely feel my truck working hard with my smaller lift and tires. Use one of Matt's tow tunes and you may want to use tow/haul mode to keep it in a lower gear when needed, at least until you re-gear (if that is the plan).

 

You're sucking fuel because you have the worst possible setup for towing economy; heavier tires, taller profile, under-geared and the engine is out of it's powerband. You need new gears, plain and simple.

4.30s or 4.56s are the answer.

 

Yeah- I'm figuring the gears are the way to go- was just looking for some confirmation.

What are you guys seeing for average boost levels when towing at highway speeds?

 

Over the last seven years pulled 12k and 15k fifth wheels. The 4.1 rear end is crucial. Truck is 4WD so sits plenty high with stock wheels & tires. Tow haul mode is essential when pulling, not sure if 04 has that option, changes the transmission shift pattern. Have never used a tune. But a few months ago updated the FICM and ED put the Atlas 40 tune on the FICM. Haven't towed since that added, discussed towing with him and hopefully will not have any adverse affects. Pulled many long trips, 2 trips to Alaska, and others to most of the western states. Many hard pulls. My speed rarely gets above 65, try to stay mostly between 55-60, if I am not on a interstate. Long pulls up steep hills the truck can easily pull down to 35-40 mph, watch the turbo and rpm and back-off if numbers get up. In the northern part of BC and southern Yukon, there are some grades that are not fun; would be easy to ruin the motor if not careful. Most important thing is to get where your going safely.

 

I can't comment on what to expect with the tune you have. Question on MPG calc: are you using GPS for distance? 37s are not only huge, they are heavy so you got the gearing disadvantage as well as all that weight to spin; then you throw in the lift and you are pushing a brick through the wind while towing another brick -- wind is going under and all around you and then hitting the trailer...

We've found that 5'ers and goosenecks in general get better mileage -- must be more aerodynamic. We ran 305s for a while until they came apart (too much weight as they were E rated but only went to 65psi), anyway they were equivalent to a 33.5" tire and we're at stock height and no tune. Even empty there was a significant difference in performance, but loaded with slide-in camper ~3500#s or so (you wanna' talk about a brick...) and about 9k worth of horse trailer, the truck definitely worked hard; particularly since we had some regular camps up over the sierras so pretty stiff climbs. We hit an all time low of 7MPG going up on one of those trips! On a less mountain type trip we see in the 10 - 12mpg range and now we're on 285/65/18Es. I plan to go back to stock size tires next -- we just have too much weight on the rear.

I think you are on the right track if you are keeping the lift and tires to go lower on gearing. Just don't expect much in the way of mileage -- there's no magic here with what your combo is.

Just as another reference point, we have a friend that has a 34' 5'er and an '04 F350 SRW 4x4 6.0 (auto). They scale out at max GCVWR, in the 22.5k range. He's at stock height and stock tires and no tune and gets 10 - 12MPG (and they travel a lot!)...

 

It looks like you just had a reality check about the capabilities of your truck. The short answer is you can't have it all.

Our truck is 2003 6.0 stock 4 X 4 with a 3.73 rear differential with the original 16 inch wheels. We pull a 10,000+ lb. loaded fifth wheel all over the United States and Canada. When we pull on the flats, we generally leave the transmission out of tow mode. We average 10-11.5 MPG hand calculated. Unless we are in steep inclines in the Rocky Mountains, the truck does a more than adequate job of pulling the trailer with little strain. On the steep inclines I drive by the tachometer with speed ranges anywhere from 50 -65 mph. Our normal towing speed is 2 1/2 MPH under the posted speed which for the most part is 62 1/2 MPH or 67 1/2 MPH. I find that over a long trip we get to where we are going just about the same time as the guy who passed me 100 miles back.

Our trailer tires, like most trailer tires, are rated to 65 MPH. I have blown two trailer tires on the interstates and there has been significant damage to the wheel wells in both cases. Prior to the 5th wheel, we had a 6500 lb. pull behind and the fuel efficiency did not degrade significantly with the new heavier trailer. We have pulled about 50K miles on this truck.

On the other hand, you have 37" tires with the same low ratio rear differential. I'm not sure what your various tunes do for you but there probably is something of a trade-off of horsepower versus torque. And torque is what you need to get your trailer off the line or to hold speed when encountering inclines. You may get some better performance by using "Tow Mode". You mention you drive at 75 MPH and in my opinion, that is about 7-10 MPH too fast for overall safety and certainly for your tires. At your speed versus 65 MPH, you probably lose about 1 - 1 1/2 MPG. Your trailer is probably a "Lite" model with 14" tires but take a quick look at the size of your trailer axle and when you lube the wheels, look at the size of your bearings. You may be underwhelmed.

As to other trailer items, you should have a brake controller and torsion bars and sway control on the trailer. I see "lite" trailers rolling down the highway without sway controllers. It's one of those funny things, you only need it when you need it.

You may want to test your fuel pressure, also. I have that on the brain right now since I just ordered a fuel pressure gauge. Good luck and safe towing!

 

Another disadvantage to your set up are the larger tires that are an off road tread pattern as opposed to a highway pattern. This creates even more drag that your engine must overcome.

I think in order to be happy, you will need a gear change like the others recomended, but realize that its gonna cost you $$ for install. And possibly a loss of milage while unloaded ( which is the way you said you drive your truck 99.5% of the time.

I have a 3000# truck camper and I pull a 6000# jeep/trailer and my stock rig does a good job. Maybe for comparison sake, you could get a friend with a stock set up to let you hook up your camper for an afternoon pull out to his favorite lunch spot.

 

I'm calculating MPG using GPS numbers.

So, it sounds like gears might be in order. I am still hoping to hear what you guys are seeing as far as boost numbers while towing on the highway....

 

Your boost is going to be jacked as long as you're bogging down the engine by trying to work it hard at those low RPMs. You're seeing the boost so high to try to match airflow to the volume of fuel desired the PCM is calculating. Spin the engine faster with deeper gears and it'll sort itself out. 1400rpm at 55mph trying to turn those 37s, move all the air out from an 8" lift, throwing 5k on the back is just making everything that much worse.

It's not going to help you to tell you that I hold about 8psi at 13k combined going 60mph, because my truck is a foot shorter height wise, my tires are 4" smaller so my effective gearing is deeper than yours, and I'm not running SRL.

 

Now I need to find a reputable shop around here to trust with a gear install. I know these can be done the sloppy redneck way, or professionally with proper care on clearances, etc. I want the latter.

 

Why don't you just use tow haul mode, and keep the trans out of overdrive?

 

I'm a south Alabama redneck and there's nothing sloppy about my truck. I also tow 10k frequently with no issues keeping up with traffic.