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ideal cruising speed for c15 acert

Discussion in 'Trucks [ Eighteen Wheelers ]' started by gunner76, Jul 23, 2011.

  1. Jul 23, 2011 #1
    gunner76

    gunner76 Medium Load Member

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    Mar 11, 2010
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    I bought a different truck today and it seems to run at a pretty low RPM at cruising speeds. The truck is a '07 9900 with a C15,13spd,3.55gears and low pro 24.5's. At 60mph in high gear the engine runs at 1200rpms, is this too low to be in the ideal range for the acert engines. The door jam on the truck is stamped 22.5 lo pro's, but the build sheet on the truck shows that it came from the factory with 24.5's. The speedo has been corrected for the tire size that is on the truck now. I like the look of the 24.5's but if I'm going to be lugging the engine I won't keep them. I've thought about swapping the set of 11R22.5's from my old truck to the new one and then switch to lo pro's when those tires wear out. I run alot of two lane roads so I'm in the 55-60mph range quite a bit.
     
    gunner76, Jul 23, 2011
    gunner76, Jul 23, 2011
    #1
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  3. Jul 23, 2011 #2
    DL550CAT

    DL550CAT Road Train Member

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    Oct 18, 2009
    Waynesburg, Pa
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    That's whats so great about the 13spd you have those half gears to keep your rpms where you want it. Which means you will spend alot of time half a gear down at the lower cruise speeds. I have the close to the same specs. Mine is a 18, tall 24.5s and 3.55 rears. I also run alot of 2 lane raods with a 45mph speed limit. It does just fine. In fact I wish I had taller gears when I get out on the inerstate at 70+mph its to high on the tach for good mileage.
    I would run it for a few weeks to get a base line on mileage then get Mr Haney to set you up with a tune. You will be very happy you did.
    Oh and you wont be lugging it at 1200rpm. It will do just fine there but I would not cruise much lower than that.
     
    DL550CAT, Jul 23, 2011
    DL550CAT, Jul 23, 2011
    #2
    gunner76 Thanks this.
  4. Jul 24, 2011 #3
    The Challenger

    The Challenger Kinghunter

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    What happened to the 379 ex Werner petes you were looking at??

    KH
     
    The Challenger, Jul 24, 2011
    The Challenger, Jul 24, 2011
    #3
  5. Jul 24, 2011 #4
    gunner76

    gunner76 Medium Load Member

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    Mar 11, 2010
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    I just didn't like the semi gloss paint on them and the paint on the two my local dealer had were in really tough shape. Besides, I'm more of an International person anyway. I've always wanted a long hood 9900 but was having a hard time finding one that met my criteria.
     
    gunner76, Jul 24, 2011
    gunner76, Jul 24, 2011
    #4
  7. Jul 25, 2011 #5
    rjmcgee

    rjmcgee Light Load Member

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    Feb 23, 2008
    Klamath Falls, OR
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    I have an 05 Freightliner Columbia with the C15 Accert, 13 spd, 3.42's, and 24.5 low pro. I do alot of California and Oregon so 60 mph is the norm, it will chug along at 1200 all day. Actually has plenty of power to deal with small hills with out down shifting all the time. Accert will pull clear down to 1100 quite well. On a long 6% grade I will drop half a gear lower than it would pull and keep it up around 1500 rpm's.
     
    rjmcgee, Jul 25, 2011
    rjmcgee, Jul 25, 2011
    #5
    gunner76 Thanks this.
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