Double over 13

Discussion in 'Trucks [ Eighteen Wheelers ]' started by DDlighttruck, Mar 29, 2017.

  1. DDlighttruck

    DDlighttruck Road Train Member

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    What is the primary reason for a 13 double over? Do you drive it differently? Are the gear shift ratios different, or just the last one?

    I understand that a 13 d/o and tall rubber gives you long legs. A lot of "coast" trucks (running coast to coast) were spec'd that way. Just looking for some more info please.
     
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  3. baha

    baha Road Train Member

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    They are good if you must go back empty every trip, they have been the reason for many 15 or more over speeding tic.
     
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  4. AModelCat

    AModelCat Road Train Member

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    This might not be the correct answer but I believe the double over 13 and 18 have an overdrive main box, which means the top hole will be overdrive regardless of splitter position.
     
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  5. gunner76

    gunner76 Medium Load Member

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    the truck in my Avatar had a 13 double over and for me it was a waste. I didn't use top gear unless I was running over 65.
     
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  6. DDlighttruck

    DDlighttruck Road Train Member

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    So the primary reason is less fuel consumption?

    I thought it was to go fast. That's why I'm asking
     
  7. DDlighttruck

    DDlighttruck Road Train Member

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    Why? Running over 65 you were lugging it too low?
     
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  8. gunner76

    gunner76 Medium Load Member

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    It's allows you to go fast and use less fuel. I think at slower speeds the Double over might actually hurt you because the engine is running too low.
     
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  9. gunner76

    gunner76 Medium Load Member

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    It ran too low RPMs at 55-60 for my liking when loaded.
     
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  10. Ristow

    Ristow Road Train Member

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    My '96 T600 had a double over and 3.90 rears. It was a great setup. 470 Detroit in it. Easy out of the hole when heavy and great cruising.
     
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  11. DDlighttruck

    DDlighttruck Road Train Member

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    This might devolve into a fuel saving thread. So, if I understand it right, you need to learn the motors optimum fuel performance RPM. Say 1400 rpm for arguments sake. Then you try to drive at that rpm.
    So if you wanna drive 85mph a 13 d/o may keep you close to 1400.
     
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