13 spd Transmission and RPM's. Best cruising gear?

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Turbrospeed, Nov 23, 2021.

  1. MRMTRANS

    MRMTRANS Light Load Member

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    I run in direct most of the time. Never had a problem after 700k miles. RTLO16713A tyranny. However, I always thought direct was getting out if the "big" hole-instead put it in 11th gear. That's when only the countershafts are turning and not losing energy in turning the other gears.
     
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  3. BoxCarKidd

    BoxCarKidd Road Train Member

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    Thanks for the education. I missed that along the way.
     
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  4. MAMservices

    MAMservices Light Load Member

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    If you re-gear, of course both sets need to be changed. The “cruise calibration” needs to be reset as well. This not only makes the speedo accurate, it allows the ecm to calculate proper fueling, with regard to correct ground speed, in relation to the rpms/tire size/ throttle pedal position, so the engine performs more efficiently. Among other things.
     
  5. Pamela1990

    Pamela1990 Road Train Member

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    I'm not even close to a transmission mechanic, never opened one up, much less an expert. But it would strike me as odd, if they built some gears weaker than other.
     
  6. xsetra

    xsetra Road Train Member

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    My guess:
    The gears that break are weaker because they're smaller or fatigued not because they are built weaker.
     
  7. wore out

    wore out Numbered Classic

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    The torque rating has everything to do with gear strength. The gears may look identical from say a RTLO16913b and a RTLO20913b. However the 20913b will be a different part number....and be harder. I do know of transmission shops that will use the 16 rated gears in a 20 trans build though to save money.

    just because it fits doesn’t mean it’s the same
     
    xsetra Thanks this.
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