• Ask TFLtruck: Ford F350 Dually – Which Rear Axle is Best to Tow a Camper Across Country?

    2018 ford f350 super duty
    2018 Ford Super Duty (photo: Ford)

    Which rear axle ratio is best for towing a large camper trailer across the country?

    Fred writes:

    I am looking to get a 2019 Ford F350 dually. What rear axle ratio would be best for a large 5th wheel camper cross country trip?

    The new Super Duty diesel comes with three rear axle ratios: 3.55, 4.10, and a 4.30. Take a look at the Ford’s towing guide chart below. The higher the numerical number of the ratio, the truck is said to have “lower gearing”. Having a 4.10 rear axle ratio means the drive-shaft spins 4.1 times per one revolution of the axle shaft that is going to the wheel.

    Truck makers are able to rate the trucks at a higher towing capacity with lower gearing. The maximum towing for the Super Duty with a 6.7L Power Stroke diesel V8 and a 3.55 axle is 27,300 lbs. The rating goes up to 31,800 lbs with a 4.10 axle, and up to 32,500 lbs with 4.30 gearing.

    Lower gearing also means the truck is able to get off the line a little better and negotiate steep mountain passes with a little more ease. On the flip side, the lower axle ratio takes down your fuel economy. The engine has to work a little harder to move the same distance.

    A gross combined weight rating of a large 5th wheel camper trailer is around 20,000 lbs. This is a weight of a fully loaded trailer. A F350 or F450 dually are required to carry so much tongue weight (likely over 4,000 lbs of tongue weight). However, having a 4.10 rear axle is not a must for a 20,000 lbs trailer. The 3.55 can get the job done and provide a little better fuel economy down the road. If you do want a little extra oomph to climb and descend the Rocky Mountains, then go with the 4.10.

    If you want to know more about towing heavy trailers with the latest 1-ton dually trucks, check out this video where we measure fuel economy on all three newest diesels.

    Andre Smirnov
    Andre Smirnov
    Andre Smirnov is an Automotive Enthusiast, Producer, Reviewer, Videographer, Writer, Software Engineer, Husband, Father, and Friend.

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    42 thoughts on “Ask TFLtruck: Ford F350 Dually – Which Rear Axle is Best to Tow a Camper Across Country?

      1. What’s the “correct” ratio? It’s weird to think there is only one ideal ratio for all trucks, engines, transmissions, and applications. But I guess the one in the Chevy is the best at everything.

        1. With 6+ speed transmissions, axle ratios really aren’t that important anymore. Most transmissions have plenty of gear ratio spread to handle anything you can throw at it while still having enough overdrive to do well on the highway.

      2. Hmmm, sounds like a fanboy statement. At least someone who knew what they were talking about would include what said ratio was….

    1. Fred writes:

      I am looking to get a 2019 Ford F350 dually. What rear axle ratio would be best for a large 5th wheel camper cross country trip?

      Hey Fred,
      How about posting the dry weight of this 5th wheel so you will get some cogent answers.

      1. Yeah right if they were getting Ford money you wouldn’t see so many articles for other brands, nor would you see an Ike gauntlet that the Ford loses in. Take the tin foil off.

        1. Does not stop Pick Trucks . com from doing stories on other brands but it is very clear that they favor Ford and get paid by Ford.

          Why would it be a stretch for the same thing to be happening here? Ford does like to operate that way after all.

          1. I pointed that out last fall when there was zero mention of the 1.3 million aluminum F-150’s recalled. They posted news reports of Ram and GM recalls but were mysteriously silent when a much much bigger recall for Ford trucks occurred just over a month later. Mike Levine is VERY active with online auto websites and frequently comments in article comment sections.

        1. @Lolchief: I agree, the question is a bit short on details for someone who’s about to spend some serious change on a truck.

    2. Depends on trailer weight. I’ve got a 15 F350 srw with 3.55 rear end. I pull a 30ft 12k (loaded) fifth wheel, and the only thing slowing me down going up mountain passes is the woman screaming next to me. More than enough power with the 3.55 gears and the new ones are rated a little higher power wise.

    3. We need to have more info to give you our best advice! What do you mean by a large 5th wheel trailer. Where do you spend most of your time. Pulling in the mountains or mostly on flat ground. Will almost all of your miles be on the interstates or will you be exploring a lot of smaller, steep, winding secondary roads with the trailer attached as well. How many family members will be in the truck and how much stuff (luggage, toys, etc.) Will you be taking. So until you can give us more detail, I think Andre covered everything well above.

    4. Gear ratio’s matter for rating only of the manufacture. 4:10’s don’t pull any better then 3.55’s in the real world cause of having 6 gears in the transmission adjust your final drive ratio…. while you may be in 3rd gear going up hill in a truck with 4;10’s the 3.55 will just be in 2nd gear and prolly do it easier then 4:10’s cause a superduty diesel in 2nd gear with 3.55’s is a slightly a lower ultimate ratio then a 4:10 in 3rd gear.

      The worst gear ratio I have every driven have been both Ram 5500’s and Ford f550’s… Both had 4:88 gears both ran about 2800+ RPM down the highway in 6th gear at 80 mph. So far outside the power curve of the diesel that these things just suck with such a low ratio.

      1. Finally someone else that knows better than to talk about rear end gear ratio’s. Only thing that matters is the final ratio. Different tranny different rear end ratio. 4:10 rear end can have a closer end ratio than a 3:55 even in first gear given a different transmission.

      2. It does matter. The closer you can get the gearing setup to match the load the better your setup will perform and the better your fuel economy. Saying that, there is far to little information given here to give a recommendation.
        First of all, be sure that the ratio you chose is within the manufacturer’s GVWR for what you will be hauling.
        As others have said, if you are pulling a lot of weight a lot of the time, go with the lower ratio. If towing is occasional and you are more concerned with FE than overall performance (when towing), go with the higher ratio-so long as you are still within the manufacturer’s GVWR.
        Modern 6-speed transmissions definitely reduce the impact of axle ratio choice but getting it right will help everything work better and reduce wear and tear on your drivetrain-the engine will be in it’s happier rpm range more of the time and the stress on your transmission, driveshaft and differential will be less.

      1. Another nail to Tesla’s coffin.

        White House weighs big cuts to mpg rules.

        NHTSA is looking at a range of options to lower future fuel economy and emissions targets, including one that would permit an average fleetwide fuel economy standard of 35.7 miles per gallon by 2026, down from the 46.6 miles per gallon under rules charted by the Obama administration.

    5. We are not talking about 4.88 gears as an option here. And also when are you going to be going 80 mph pulling a 20,000lb. trailer. Let’s get real here.

      1. 3:31 was the best gear I drove in a superduty. 6 gears in the transmission had perfect ratios for 15,000 lbs loads all day long. At 75-80 you were at peak torque in 6th gear. 4:10’s with the tire sizes puts all these trucks at unnecessary high RPM in their tallest gears. on 3:31’s The transmission would shift to one of its lower numerical transmission gears if needed. Once outside 1st gear in transmissions the rearend ratio doesn’t matter. Heck semi’s are running around with high rearend ratios. Semis typically out on the highway wont even run remotely close to 4.10 like low gears. Kills the mpg as it turns more rpm then needed and if they need power they can just down shift to a lower gear just like these pickups will shift to a lower gear when needed.

        Nothing to have semi pass you at 80,000 lbs if you are driving out west… Freeway speeds are 80 mph with 4 axles and under 26,000 lbs. 70 for 5 axles or more or over 26,001 lbs Which means almost everybody including semi’s are running at 75 mph. cars and pickups not hauling are 80+ mph. Anybody rolling along at 60-65 are a huge hazard.

        Fords diesel makes it peak torque at 1800 rpm. f350 dually comes with 245/75 R 17. So its tire is 31.5 inches in Diameter.
        In 6th gear
        4.10 gears at 70 mph you are spinning the engine at 2051 rpm
        3.55 gears at 70 mph your are spinning the engine at 1776 (peak torque and fuel economy)

        So for the original poster asking the question 3.55 would be the choice I would say if the manufactures rated capacity will handle the trailer. It will be a better highway tow rig with 3.55’s vs 4:10’s

          1. Running around the west about 15.5-16 mpg hwy at 80-85 mph
            Towing 10k travel trailer about 8.5-9 mph running 75ish+ mph.

            At work the 5500 cummins that weighed 13k no trailer would get 8-8.5 mpg at 78 mph… governed at that speed.

            F550 with 6.7 at 14k lbs no trailer at 83 mph governed would get 8.2-8.7mpg

          2. Why is everyone still misusing the colon for gear ratios? It’s 3.31, 3.55, 3.73 etc. Not 3:55. It’s 3.55 rotations of the tail shaft for every rotation of the axle. Not 3 rotations of the drive shaft for every 55 rotations of the axle. Come on people!

    6. MPG isn’t just a function of rpm. Throttle position is actually more important. Since you will be pulling, go for the largest gear. If you are running around empty, then the smallest gear. Some of each, go for the in-between.

      1. X1. And this is why ford only has one gear ratio available for their best rv pulling rig, the f450 and that gear ratio is 4.30.

    7. I always opt for the lowest ratio. 4.10 in this case. It simply makes the truck feel faster than it is. To me, that’s more important than 1 mpg on the highway.

      1. Agreed. Why would anyone that just spent $125,000-$150,000 on a new truck and trailer care about using a little more fuel. “Penny wise and pound foolish” perhaps! I bought my f350 gas dually with the 4.30 gears and i’m very happy with its power and fuel mileage.

    8. With that much power any of the ratios will get the job done. Question is how often are you really pulling 20k. If you only pull once a month and do a lot of unloaded highway otherwise get a 3.55. If you are hooked up several times a week get a 4.3. Load on engine driven by weight and drag whether loaded or unloaded is going to dictate mpg much more than the gear ratio on these types of vehicles.

    9. The 4.30 gears only come in the F450. There are lots of reasons not to get one.
      As between the 3.55 and 4.10, in loaded use, the fuel savings will be nominal, at best. Either gear will do fine with a 10 ton trailer. In resale, the 4.10s will be more desirable to someone looking to pull half again as much.

    10. I have never said “This axle ratio seems geared to low” Speaking from personal experience. I always look for the lowest ratio. That being said its a complex issue dependent on engine torque, transmission ratios, tire size and throttle mapping. Modern throttle mapping(biased for fuel mileage) with out a tuner of some sort tends to make response sluggish, and a higher numerical rear end helps. Maybe the highest numerical ratio is not always the most perfect, but better to be geared lower then higher.

    11. I run a v-nose enclosed gooseneck trailer daily that is 15k lbs daily. My truck is a 2016 ram 3500 srw with the cummins and aisin Trans. My rear differential is 3.42 and my daily pull is mostly highway for 70-80 miles going 62-70 mph. Most of the hills the truck has no issues, although I have encountered hills that the truck would slow down on. In saying the with little info on this fifth wheel the best towing mpg will be hard to figure out. With my setup every small incline drops the transmission to fifth gear which is increases the fuel consumption. Where as if I had the higher ratio my truck would stay in sixth longer and therefor offer better fuel economy. With the large flat surface of the fifth wheel trailer and depending on your trailer weight the 4.10 would be my choice. 2 years ago when I was looking at trucks and with my limited trailer pulling the lower ratio would have been my answer. With 50k miles of towing in the last 1.5 years my opinion has changed.

    12. I drive a 2015 f350 dually at work with a 12K boat that’s 11.5ft tall. The 350 has 3.73 gears in it. It pulls that load wonderful. In the hills of WV,OH,PA I average 9-10mpg w/boat and have seen as high as 18mpg unloaded highway trips.
      With our smaller 7300 lb boat we get between 10.5-11mpg.

    13. This was clearly a paid Ford ad, they do this same crap over at PUTC site.

      I would not buy a Ford just because of the way the try to fool people with these phony ads.

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