81 COE Freightliner w/cummins help

Discussion in 'Trucks [ Eighteen Wheelers ]' started by FarmerBob, Nov 7, 2009.

  1. FarmerBob

    FarmerBob Bobtail Member

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    Nov 7, 2009
    Tiffin, Ohio
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    Hi All
    I'm new to big trucks and have just purchased my first truck.
    It's a 1981 COE Freightliner with a 290 cummins (I believe).
    Truck was purchased by me with a grain hopper trailer I plan on using to haul grain from my farm to a local elevator a few miles away.
    The truck runs well and seems to be in good conditon.
    I believe the truck has a power divider type rear drive but I cannot find the switch on the dash. I do see a switch or two that are missing/broken.
    My question is: Would the truck have this switch? If so, where would it be located (I am looking for a manual if anyone knows where I can get one).
    How does it work? Air ? Electic?
    Do I need to make sure the divider is able to turn on/off to prevent breaking something?
    And lastly... I have not used the truck yet but will soon and I believe that it will be underpowered for the trailer behind it.
    I have done some reaserch and there seems to be a (button) that can be replaced in the injection pump that will give it a few more horses.
    I would like more information on that also.... pros /cons.
    I am quite mechanically inclined as I do 99% of the repairs on our farm.
    This is my beginner truck/trailer combo and hopefully will be a good experience.
    Up intill now we have used 16,18 and 22' straight trucks so this will be all new to me.
    Any comments will be appreciated.
    Thank you for reading this.
     
  2. 1989 Pete

    1989 Pete "Pine Tree Eater"

    Congrats on ya truck!!!!
     
  3. 69W900A

    69W900A Bobtail Member

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    Nov 2, 2009
    This side of No Where
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    The power divider on a COE Freightliner is usually mid way up the R/S dash panel toward the windshield. It'll be an air switch. If the switch is broken it'll only have 1 diff driving, it takes air SUPPLY to shift the power divider. Although the shift lever in the diff could be stuck or some other mechanical problem. Or if the switch lever was broken off in the engaged position and still holding air or something else crazy like that.

    You can change the button in the pump, but I'd find out what engine and CPL you have first. 81 should be a Big Cam, probably a II. You can probably reset it to 350 with no problem, as normally the 290,335 and 350's used the same cams, pistion kits, etc. Have a pump shop recal the pump, might need a different injector and turbo depending on what you have now. How much do you want to spend on the HP uprate?

    For cheap you can go down a button or two and crank up the screw found in the throttle shaft for a little more power, but be careful with this as you can get one hot doing that.
     
  4. FarmerBob

    FarmerBob Bobtail Member

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    Nov 7, 2009
    Tiffin, Ohio
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    Hi 69W900A!
    Thank you for the reply. I am more concerned about the divider switch as I'll probably need some extra traction getting out of the fields.
    I don't want to break anything if it's not working properly too!
    I'll check for it tomorrow.
    As far as the button I'd just go for a little more power, something that won't sacrifice reliability. Where do I look for the buttons ?
     
  5. 69W900A

    69W900A Bobtail Member

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    Nov 2, 2009
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    The button is under a cover on the rear of the pump. You'll need to pull the old button out and get the number off it to start with. You can get other buttons from Cummins or any good pump shop. Don't make real drastic size changes, change a couple sizes and then try it. You'll want a boost gauge and pyro to make sure you haven't leaning on it too hard.

    Follow the lines from the diff up to the dash and figure out what switch you need to replace. Or take the line loose at the diff and start flipping switches until you hear air in the line at the diff.

    You won't brake it driving it around in diff lock, you could brake an axle if it has axle locks (which I doubt). Driving it on dry pavement with the power divider in diff lock will be harder on tires tho.
     
  6. FarmerBob

    FarmerBob Bobtail Member

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    Nov 7, 2009
    Tiffin, Ohio
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    Again, Thanks bunches for the information!!!
    Do the button numbers go up or down for more fuel/power?
    Thanks for the tips on the dif/lock. Again, I'll be looking at it tomorrow
     
  7. 69W900A

    69W900A Bobtail Member

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    Nov 2, 2009
    This side of No Where
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    Lower number more fuel. I should also mention, be careful when you pull the snapring for the plunger, there is a spring behind it. Don't loose any of the parts, you're gonna need all of 'em.
     
  8. dairyman

    dairyman <b> Hopper Thread Greeter</b>

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    Oct 31, 2009
    Ky.,wait'n in line
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    welcome farmerbob, after you get your '81 coe up and runnin, check out the section on hoppers,dumps,o-o and drivers, in ask an o/o section. these folks have some good info. i see your from ohio, do you know where washington court is? i have hauled in there some. anyway,welcome to forum, good luck with your truck and hopper! finally got a good week of weather,NO RAIN !!!
     
  9. MrBullfrog92

    MrBullfrog92 Bobtail Member

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    Nov 8, 2009
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    I have got to ask as i havent seen this information and it seems it would be pretty pertinant to what you are asking but is this truck a single rear drive or double???? AKA single or twin screw??? If it is a single screw its not gona have a power divider.

    A power divider is one of the most misunderstood pieces of equipment on a truck that I have ever seen. to understand a power divider we first must understand what a differential is. a differential is a device that takes up the difference in rolling rpm in the left and right tires. why would there be a difference? not all tires are going to be exactly the same diameter as there is small differences in the circumfence from manufacturing. if the axle was solid all the way through it would ruin drive axles and tires if this difference was not dealt with. look at it this way if you take a pencil and put a large ball on one end and a small ball on the other end whats gona happen when you roll it. its gona want to turn right? so you can imagine what happens when you try and force this set up in a straight line. something is gona have to give somewhere. Ok so now understanding that you will realize why when you get in some snow it is possible to slip just one wheel. the power is transmited through the differential to the wheel with the least resistance. likewise in a dual rear end set up each drive axle has a differential.

    Ok so the best way to describe a power divider is to call it a differental. in fact thats actually what it is. just as we need a way to take up the difference in the left and right there will also be a difference in front and rear axle. when the power divider is locked basically what you are doing is locking up the third differential (power divider)that is between the two drive axles. the drive shaft is now locked togherther and power can now be transmitted to both drive axles.

    Ok so with the power divider unlocked you will only need to slip one wheel on the front or rear axle to be stuck. the power will be transmited through the drive shaft through the power divider differential to the drive axle with the path of least resistance then through the drive axle differential path of least resistance and spin the wheel with the least resistance. With the power divider locked and that differential now taken out of the equation the power will be transmitted to both front and rear drive axles. that power again will be transmitted through both front and rear differentails and out to the wheels with the least resistance. So now I hope that you can see with the power divider locked in you will need to slip at least one wheel on the front AND rear drive axle instead of just one front OR rear without the power divider locked to now be stuck.

    Ok now that we know that if you have a single drive axle truck then no you do not have a power divider. if you have a twin screw drive axle truck then yes you do have a power divider. the power divider actator is going to be on the front drive axle. its going to be near the front by the input shaft. Most usually its on the passanger side. its going to look very much like a small air brake chamber but not always. at any rate there is going to be an air hose going to it but could be electrical to however this is very rare.

    I saw you say you could use more traction. Please understand that a power divider will not give you more traction. traction is a function of how the tire grips the surface in which it is trying to drive off of. what it will do is give you a way to transmite power between the front and rear axle in the hopes that either the front or rear axle has enough traction to both tires as to not get stuck.

    I hope this all makes sense lol.
     
    lv gn and Baack Thank this.
  10. FarmerBob

    FarmerBob Bobtail Member

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    Nov 7, 2009
    Tiffin, Ohio
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    Thanks Bulfrog.
    Some good information! Yes it is a twin-screw , my mistake for not mentioning that!
     
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