More of a medium duty issue...

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by wlhequipment, Aug 16, 2022.

  1. wlhequipment

    wlhequipment Bobtail Member

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    Aug 16, 2022
    denver, co
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    Hi folks,
    First post here. My name is Pete, and I hang out in Denver, CO. I'm looking for a little guidance from people who know how to drive heavy things. I run a service truck it's a 1985 International S-1954 with a mechanical DT466 and an Allison automatic trans. I'm running at right about 20K lbs, almost all the time. My load rarely varies like most yours do (I assume). Anyway, my issue is the transmission, I hate it, and I want a manual. I have a chance to pick up an Eaton Super 10 real cheap. My rig doesn't have air, but I can add it, so that won't be a problem. I'll have to change lots of stuff like the driveshaft, install driveline brakes, install manual clutch stuff etc etc. No problems there. My concern is, that trans is supposed to be behind a much bigger motor, and wants to be shifted at 1200-1400 rpm. I think I can get an SAE2 housing for it, but my main concern is that shifting rpm. The DT466 runs up to 2700 rpm, and doesn't even wake up until about 2000 rpm. If the trans wants to be shifted at 1400 rpm max, won't that pose a problem, especially during upshifting in the mountains? I would have to shift the trans below the point the engine is making any power; I won't even be able to get out of my own way, I'm thinking. Thoughts?
     
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  3. lester

    lester Road Train Member

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    Why do you think the transmission wants to be shifted between 1200-1400rpm?
     
  4. SmallPackage

    SmallPackage Road Train Member

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    Marion Texas
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    Manual transmissions don’t care what rpm they are shifted at, only engines do. Not sure but super 10 may not be best choice for a low torque, low hp engine. I assume you probably around 230hp at 800 ft. Lbs? Or less? The super 10 may be geared to high for the output and may make that little engine work harder then it should to pull through the gears. Just a thought.
    Research the gear ratios along with your rear gear and see.
    I totally get the smoking deal on the trans but Any regular 10 may be a better choice.
     
  5. SmallPackage

    SmallPackage Road Train Member

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    As an option Look into spicer 6 speeds. They are good trans behind medium dutys. I have one in my ‘99 FL 60 behind a Cat 3126B with 3:90 Rockwell rear. Have over a million miles on it with no trans problems at all ever and only on 3rd clutch.
    No air needed to be added for trans to shift either.
    And they use the smaller bell housing.
     
  6. wlhequipment

    wlhequipment Bobtail Member

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    Aug 16, 2022
    denver, co
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    Thanks guys, I'll try to answer everything in order:

    I'm hanging up on the 1400 thing, because in the book for this trans, it says not to downshift above 1400, and in the "engine speed vs vehicle speed" graph, it shows all upshifts happening below 1400, so I'm assuming it doesn't like going into gear if the input shaft is over 1400. Is that not accurate?

    Sheet, I'm nowhere near 230HP. Maybe 180 - 190. It's a mechanical DT466 that's had some upgrades, but not alot. The AT545 that's in there now has 4 ratios, ranging from 3.45 to 1.00. The super 10 goes from 9.9 to .76. I'm hopeful It'll work ok. A 6610 would be a better choice, but that's not in the cards at the moment.

    I drove a spicer 5+2 and I was always so #### clumsy trying to knock it into gear, I wouldn't go Spicer again. That was just frustrating.
     
  7. Dave1837

    Dave1837 Road Train Member

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    I've always seen those trucks paired with nothing more than a 7 speed. You won't have issues with the trans shifting above 1400, but that seems like a lot of transmission for not a lot of motor, just my opinion. If you don't mind adding air I'm almost positive you could find a 2 speed rear end somewhere and have a 5+2. Simple, durable and cheap setup
     
  8. wlhequipment

    wlhequipment Bobtail Member

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    Aug 16, 2022
    denver, co
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    This certainly isn't going to be real cheap. I have to add a clutch, bellhousing, flywheel, air, and possibly do some fancy footwork to get a driveline brake installed. The AT545 has a drum brake on the output flange that's the parking brake for the truck. The Eaton doesn't, so I'll have to figure out how to install / fabricate one. This is starting to sound like a giant PITA.
     
  9. BoxCarKidd

    BoxCarKidd Road Train Member

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    I found a small bell housing for a 9509. 1 3/4 shaft with a clutch brake. Shift cover in correct location and it was a piece of cake.
    Worked great in a spreader truck. We had air brakes. No park brake problem.
    Super 10 is way to large for your application.
     
  10. wlhequipment

    wlhequipment Bobtail Member

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    Aug 16, 2022
    denver, co
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    What's the specific drawback to using a trans that's too big? I'm assuming you mean torque - wise.
     
  11. SmallPackage

    SmallPackage Road Train Member

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    Big as in size. To much needless mass and weight hanging off the back of engine for what you want to accomplish.
    Like has been mentioned a 9509 or even an old tried and true RT-910 will be great choices if found. They both mate up to smaller bell housings easily.
     
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