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    Thread: Dually VS tandem axle pick-up trucks?

    1. Member Bakounine's Avatar
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      05-06-2011 10:14 AM #1
      Perhaps someone can school me on this. Why is it that we only see dually pick-up trucks on the civilian market while tandem axles seem more accepted in the military?

      What are the advantages and disadvantages for each?

      It seems to me that a tandem axle would be able to carry more because, well, it's got two axles... I guess the turning radius would be bad, but the the sheer width of a dually doesn't make it much more city-friendly.

      Cost? The new Ram dually has an all metal dually-specific bed instead of the traditional grafted-on fenders, so makink a tandem-axle bed would probably be easily feasible and not to costly, no?


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      05-06-2011 10:19 AM #2
      Because as much as marketing wants to tell you otherwise, all "civilian" pickups are light duty vehicles. None have the payload or towing capacity to warrant more than one rear axle.

    3. Member mobile363's Avatar
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      05-06-2011 10:22 AM #3
      A 3 axle vehicle also requires a higher license.

    4. Member clutchrider's Avatar
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      05-06-2011 10:24 AM #4
      Dodge T-Rex, saw it at the Big E a few years ago. What an awesome looking truck.

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      05-06-2011 10:36 AM #5
      Quote Originally Posted by mobile363 View Post
      A 3 axle vehicle also requires a higher license.
      x2

      Besides more axles equals more money. Also 26,001 lbs requires a CDL, so the extra capacity of another axle is not needed.

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      05-06-2011 10:39 AM #6
      The center axle would be very expensive.
      Typical rears have a pinion yoke, or 3rd member to receive power from the driveshaft, then 2 axle shafts. In your average 1/2, 3/4, or 1 ton applications, most axle loads are under 10,000 pounds. A dually dana 70 or 80 could be up around 15,000.
      The axle tube itself is much stronger, and the hubs are different, but other than that, a dually axle and a SRW (single rear wheel) axle share the same axle shafts, gears, carriers, brakes...
      To get that power take off from the center axle, to drive the rear most axle, I know a rockwell has it off the top of my head, which is why a deuce & a half has a PTO

      See that there's an input & output shaft on top of the diff in the top right corner? That's what's cost prohibitive.



      Because most pick-up axles are something like this, with only an input yoke:



      The T-rex has something like this, although I'm not sure if this is the OEM unit:

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      05-06-2011 10:43 AM #7
      A single heavy duty axle is cheaper to build and maintain than two medium duty axles. Costs start to spiral when you add in additional suspension components needed for an extra axle. Think about things like the number of shocks, springs, spring hangers, u-joints, and sway bars needed to hang another axle under a pickup.

    8. 05-06-2011 11:01 AM #8
      Quote Originally Posted by Bakounine View Post
      Perhaps someone can school me on this. Why is it that we only see dually pick-up trucks on the civilian market while tandem axles seem more accepted in the military?
      Probably bc you aren't/haven't been in the "military". Read up on the Commercial Utility Cargo Vehicle, or CUCV. A 4WD Dually CUCV is one tough SOB.

      Tandem axles are more $ and take up a great deal of space, thus are typically found on much larger (size & capacity) vehicles.

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      05-06-2011 11:48 AM #9
      Quote Originally Posted by patrickvr6 View Post
      A single heavy duty axle is cheaper to build and maintain than two medium duty axles. Costs start to spiral when you add in additional suspension components needed for an extra axle. Think about things like the number of shocks, springs, spring hangers, u-joints, and sway bars needed to hang another axle under a pickup.
      Not only costs but weight as well. Plus the MPG penalty...
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      05-06-2011 12:02 PM #10
      I imagine that with advances in metallurgy and tires, tandem axles will become more and more relegated to obscure super-high capacity vehicles, and on trailers where you don't have to deal with driving the wheels and space isn't so much a constraint.
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      05-06-2011 12:10 PM #11
      I'm gonna throw some Eatons on my lifted F-350 for extra bro-dozeability.

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    12. Member mack73's Avatar
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      05-06-2011 12:24 PM #12
      Quote Originally Posted by mk3er View Post
      I'm gonna throw some Eatons on my lifted F-350 for extra bro-dozeability.


      Unless I am missing it, who said this had to be a 6x6

      Use the standard axle for the front wheels, then just a non powered axle for the rear wheels. A little bit more weight, but no more complexity or requirement for multiple drive shafts and rear ends over a standard dually.
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    13. Member Bakounine's Avatar
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      05-06-2011 12:25 PM #13
      Is it even necessary to have power to the third axle? If it's only for extra support, perhaps a hollow tube with brakes at each end would suffice?

      As for the argument about hd vs light duty, some UTVs use a tandem configuration in the back, so wether it is for a light, medium or heavy duty vehicle, I think the point of adding more capability is still valid.

      Edit: Mack73 beat me to it.
      Last edited by Bakounine; 05-06-2011 at 12:32 PM.

    14. Member mk3er's Avatar
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      05-06-2011 12:29 PM #14
      Quote Originally Posted by mack73 View Post
      Unless I am missing it, who said this had to be a 6x6

      Use the standard axle for the front wheels, then just a non powered axle for the rear wheels. A little bit more weight, but no more complexity or requirement for multiple drive shafts and rear ends over a standard dually.
      So what we're really talking about here would be a tag axle setup?



      Though not necessarily a drop axle, more like what you have on buses/motorhomes?
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    15. Member TurboWraith's Avatar
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      05-06-2011 12:32 PM #15
      Quote Originally Posted by Bakounine View Post
      As for the argument about hd vs light duty, some UTVs use a tandem configuration in the back, so wether it is for a light, medium or heavy duty vehicle, I think the point of adding more capability is still valid.
      Sure it is. I think the two main points of why it isnt done (other than cost) is;

      1. Licensing issues
      2. Tight turning on pavement sucks in these types of vehicles. I dont know if you have ever driven even a 6x6 ATV/UTV before, but the tire scrub from the rear tandems creates a lot of resitance. Its worse on larger vehicles. If you guys ever get behind the controls of something like this:



      You'll see right away how much power it takes to overcome that tire scrub. Traditional duallys are just easier to drive, even with the incrased width.

    16. Member Shomegrown's Avatar
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      05-06-2011 12:33 PM #16
      Quote Originally Posted by Bakounine View Post
      As for the argument about hd vs light duty, some UTVs use a tandem configuration in the back, so wether it is for a light, medium or heavy duty vehicle, I think the point of adding more capability is still valid.
      It's not valid. A single axle is more than enough to take the payload into the CDL requirement category.

      The only purpose of another axle would be "to look cool".

    17. Member patrickvr6's Avatar
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      05-06-2011 12:36 PM #17
      A 3rd non driven axle is referred to as a tag axle and it just isn't necessary in trucks with this capacity. Without driving the extra axle you would have less traction available than you would with a true dually becuase you have fewer driven tires.

      There isn't much difference in a 1-ton truck and a 1-ton dually, mainly the hubs and rear brakes. The same isn't true for a 3 axle truck. It all comes down to expense in relation to the extra capacity provided.

      In some areas tolls are also calculated with the number of axles so a 3 axle truck would be more expensive to operate.

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