I say your trucks tired or has a problem. I frequently tow a 16' box trailer with an 8.5 X 8.5 frontal area that weighs 6700 lbs. gross and I have no problem maintaining speed. In extreme cases it shifts down but I can set the cruise at 65 and drag that thing all over the country and never lose speed. I have an 04 FX4 SC with an Edge set on level 2. Like someone else said, when I click the tow button(lock out OD) the truck seems to perform much stronger. Maybe all in my head but my seat of the pants dyno says my shift points are different and the power curve is better when using the tow button!?

 

With 7k behind the truck, you can get up to speed from a standing start moving up a slight grade without the truck seriously bogggin and accelerating very slowly?

Anybody in Socal with a similar truck want to test pull this trailer to compare? Maybe there is something wrong with the way my truck is running, but Ill never know without trying another truck with the same setup.

Im looking for a 4.30 now, Im thin king the 4.10 may not be enough when I go to replace the tires at some point.

 

I guess "seriously bogging" is a relative term. Can I tell the weight is back there when starting on a hill? Yes. Do I ever feel in danger of not clearing an intersection or cresting a hill? No. Actually I can't believe how well it pulls it. My last trip through Pennsylvania mountains I averaged 14 MPG and never once felt short on power. Granted one time on a several mile long grade, by the time I reached the top I think it had shifted down to second and the RPMs were way up there, but I maintained speed and handled fine. You just have to keep an eye on the tranny temp when you do that.
If your wanting to take off from a stop the same way you do when running empty your going to be very disappointed with any truck, even a diesel!

 

7000 pounds, 14mpg through the mountains? Anybody getting 14mpg with that kind of load through the mountains? You want to trade trucks...

Mine drops into second towards the bottom of a grade and pulls 4000 rpms all the way up. All but steeper ones it will maintain speed but work high in the rpm range.

 

My dad's 04 gets about 11 mpgs if taking it easy pulling his 7k lb camper on flats and over passes. 14 seems odd.


What size tires do you have on it now, and what size did you have before. Switching back to stock size or just a little smaller would give you better towing, and 4.10s might be all you need. But if you stay a little bigger than stock with intentions to go a little bigger 4.56s might work good.
IF you could find some 4.30s that would be great. NOT very many companys make 4.30s for all axles, but they are out there.

 

Ive seen about 11 with the trailer. 14 would be a gift from God.

I cant find 4.30s anywhere. Im gonna stick with this tire size (275/50/20 take offs from a King Ranch) and go for the 4.10. Stock size was 265/65/17 I think. When these tires are done maybe a 265/55/20.

The 4.10 plus the mandatory tuner should be my best bang for the buck. I would imagine the tuners keep it in first gear more agressivly(?), curently it seems to short shift into second and thats where it falls on its face. Which tuner? Im sure thats answered already in the forum, Ill go track it down.

Thanks again for the input.

 

You are not going to notice much of a difference going from 3.73 to 4.10. I think you will be disapointed. If you tow on a regular basis you need at least 4.30, personially i would go with the 4.56. There is a lot of people on this site that will tell you that these trucks work just fine with 4.56 gears.

I was thinking about regearing my truck with 4.30 gears. And i only have 33x12.50s and i never tow anything.

Thats the great thing about overdrive.... you can have low gears and still be able to cruse... Unlike my 78 that screams down the road at 60mph and 3000 RPM.

 

The 14mpg was an average over a 600 mile trip which included the flats through Ohio, but yeah, I'm extremely happy with how it does. Surprisingly when I'm just running around town empty I'm lucky to get 16 which I thought sucked, but then again when I pull the trailer I drive like an old man and when I'm empty I drive it like I stole it. These numbers are according to my Edge and I only have 17" wheels, looks like everybody else is running 20s.
No, I don't want to trade trucks.

 

This raises another question, it looks like most FX4 trucks have 20" wheels and mine only has 17". Did they make them both ways or did mine get switched somehow? I bought my truck used from a dealer with only 7400 miles on it and everything looked factory. I thought about taller tires but everything I read says it will kill my towing.....?

 

They made them both ways. IMO, you're better off with the smaller wheels, especially if you tow. You also get the benefit of a smoother ride and I think trucks should show more rubber than wheel anyway. Big wheeled trucks reminded of pavement queens that were never made to go anywhere but the highway..... but again, that's just my opinion.
I didn't like the tires I had on my truck (255 70 17 Americraps), so I went with a slightly larger tire to add a little beefier look and a better ride and quietness by going with 275 70 17's. I have no complaints.

 

I found a 4.30! This will be much better, if I think its too low I can always put on slightly taller tires to dial it in. Putting smaller tires on seems downright un-american.

National Drivetrain has them in stock: 800 507-4327

I cant wait to give this setup a test ride.

 

The 20's you have on there are roughly within 1/4 inch (taller) of the original 16's in diameter. So you likely aren't seeing much difference vs. the stock tires. Going to the 265/55/20's adds almost an inch of diameter to your tires, probably between 100-200 rpm drop in 3rd at 65 mph. The 4.30's will bump your RPM about 400 RPM at 60 mph in 3rd (3000-3100 rpm) with your current tires.

 

I just had a reputable tranny shop tell me they have had a zero success rate installing aftermarket gears in 04 and 05 F150s.

Anybody else heard this?

 

huhhh... Did they say what went wrong? Rear end gears are pretty straight forward, they get changed all the time and often by shade tree mechanics. I can't believe a tranny shop is having trouble doing it.

 

They couldnt get them adjusted correctly and refuse to use anything but Ford parts now. Two places are telling me this same story now. 4.10, 4.56 from Ford, no problem. 4.30 from anybody else, not gonna do it.