2012 Ford F-250 Rear Axle Ratio

  • 2012 FORD F-250
  • 6.2L
  • V8
  • 4WD
  • 21,000 MILES
We are buying a 5th wheel toyhauler and they tells us that our 3.73 axle ratio is not capable of pulling the 5th wheeler. Our Toyhauler is a Heartland Road Warrior 310 with a gross weight to 15,500 pounds. We are told that our 2012 Ford F-250 does not have the capability to pull it. My question is: can we change our rear axle to improve this ratio to include, if required, upgrading to an axle for dual wheels?
Do you
have the same problem?
Monday, October 20th, 2014 AT 9:07 PM

1 Reply

You really have the wrong truck for such a big trailer. If you change the rear axle ratio, you'll need to change the front one too. They have to be the same. You can accomplish the same thing by driving in second or third gear when pulling a trailer. Be sure you know where every gas station is located.

I have a friend with a body shop who specializes in less-than-one-year-old smashed trucks. He sells them mostly to farmers in the area, and because they're all hauling trailers, 99 percent of his rebuilds are Dodges. He always has a waiting list for those trucks but there's a lot of competition for them when he buys them from insurance companies.

Right now for his personal use he has a '99, a 2006, and a 2012 that he finished a few months ago. All are dually diesels that are capable of 22 - 24 miles per gallon unloaded. They're all "chipped" too. The 2006 reminded me of the ride I got in a Viper a few years ago, but he doesn't drive that one much because it has a manual transmission. For his latest project, the 2012, he cut two frames in half and used 60 percent of each one to turn a 2500 Megacab into a dually with an 8" box. This is longer than anything available from any manufacturer. This past summer he moved his sister back from Texas to Wisconsin. To haul all her crap, ... Ahh, ... I mean STUFF! He built an 8'-high box around a 32' goose neck trailer, and loaded it full. Halfway back he snapped all the wheel studs for one pair of trailer wheels, then had to chase tires through a field. A company that repairs semi trailers on the highway could not lift his trailer. They had to go back for twice as much equipment. Up to that point he had no trouble keeping up with traffic going 70 mph. He said it did cut his fuel mileage to around 14 mpg, but that's still at least double what any gas engine would get pulling a much smaller and lighter trailer.

He used that same trailer earlier to haul 40 large round bales of hay off a muddy field for a farmer. They got their Ford single-axle diesel stuck trying to pull 14 bales on a smaller trailer. Found out later those bales weigh about 1000 pounds each. That farmer's truck is for sale now, but there's no takers. He is waiting for the next Dodge my friend rebuilds. I've driven that truck too to evaluate it for Ford's all-too-common alignment and tire wear problem, and was real surprised at how little power it had. Ride quality was okay, but you buy a truck to do work, and he can't.

Understand too that for specialty vehicles, Chrysler has a different approach than other manufacturers. In the early '60s, in NASCAR, they designed the highly-sought-after 426 Hemi engine specifically for racing, then they "detuned" it to make it not-so-powerful for street use in production cars. GM and Ford took their engines that were perfectly fine for street use and tried to beef them up for racing, and they couldn't hold up to the added stress. The same is true with their diesel engines. They were originally designed to produce a lot more power, but then were detuned for use in pickup trucks. The internal parts are still the same and just as strong, and their power is still pretty impressive, but there are modifications you can make to take advantage of the engine's capabilities.

As a suspension and alignment specialist, I've driven a lot of different vehicles, and it becomes real easy to tell what has power with stability and what just makes a lot of noise and smoke. If you're serious about pulling a big trailer, especially a fifth-wheel, forget a gas engine completely. If you'll be happy with 5 mpg, buy a semi with a flatbed trailer. Instead, forget the flashy and misleading tv ads, and the high-pressure salesmen who are trained to know what you want to hear. Test-drive a number of different trucks. Take particular note how much more power the diesels have, then remember there's a lot more you can do later to boost that power a lot more. You can modify a gas engine too, but the power increase won't be nearly as much, and it still won't come close to matching a stock diesel engine.

The axle ratio in your truck is meant for fuel mileage, not pulling power. That tells me the truck was never intended to be able to pull a big load. 15,000 pounds is a tiny load by pickup truck standards. I drag a tandem axle enclosed trailer to an old car show swap meet every year, and I do that with a rusty old tired '88 Grand Caravan minivan. I need a good tailwind to hit 65 mph, and obviously this isn't what the vehicle was designed for, but that trailer loaded weighs over 4,000 pounds. Your truck should be able to drag around a lot more than four times as much as an old minivan.

Remember too that the weight of the trailer you want to pull refers to what you'll be pulling, stopping, and turning, not carrying. My trailer would flatten my van, but all I'm doing is getting it going, then aiming it. With your goose neck trailer, you will barely notice it's there when going around curves if you have dual rear wheels. You'll learn to be busy paying attention to your driving with a single-axle truck. Also, in the past, to turn a truck into a dually, besides installing that axle, you had to bolt on fender extensions to the box. I don't know if this applies now to all brands, but I learned that on the Dodges, the boxes are built and shaped for the dual rear wheels so you have to switch boxes. My friend's came out of Detroit from a salvage yard that buys truckloads of over-runs right from Chrysler. His box was from a truck Chrysler built to experiment with running a diesel engine on compressed natural gas. The second frame came from there too. It had never been installed. If you're close to that area, new, never-installed parts are readily available for projects like this.

I've never owned a pickup truck, but I've driven a bunch of them, and I've listened to many stories from people with experience. You will definitely not be happy pulling a big trailer with any truck with a gas engine unless you're just going short distances. Even then, it will be embarrassing to be passed up by a nature-lover on a bicycle!
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Tuesday, October 21st, 2014 AT 10:04 PM

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