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Thread: Auxiliary Transmission

  1. #1
    Senior Member amunderdog's Avatar
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    Auxiliary Transmission

    My old LN 8000 is in need of lower ground speed under heavy load (Off road) and just better gearing for this terrain.
    It has a 8.3 Cummins and a six speed trans.
    Low gear at working RPM's is about 7Mph.
    That is way to fast for me and the truck.
    So i could swap out the transmission. But that would be big money. Maybe more than the truck is worth.
    Or i have laying out here a Spicer 6041 4 Speed Auxiliary Transmission.
    Trouble is it has yokes for a medium duty drive line.
    My truck has a heavy duty drive line.
    Do they make heavy duty drive line yokes for this transmission?
    If so where would a person find them?

    I know it is a little rough.
    It is a work in progress.
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  2. #2
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    Auxiliary Transmission:

    Quote Originally Posted by amunderdog
    Or i have laying out here a Spicer 6041 4 Speed Auxiliary Transmission.
    Won't you need your drive shafts modified, amunderdog...

    You'll need a shaft from main, to auxiliary, to differential.

    Who ever reworks your drive lines, could put on what ever yokes you need.

    Or, am I thinking wrong here...

    Might be time to go to bed... LOL


    OCR...

  3. #3
    Senior Member amunderdog's Avatar
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    I are Poor
    So the "Who ever reworks your drive lines" will most likely be me.
    That is why i am trying to determine if the larger yokes are available.
    And if so, Maybe from where?

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    I think the best way to go is with a 2-speed rear end amunderdog.I know you have the spicer auxiliary on hand,but with the trucks short wheelbase you may have trouble finding room for the auxiliary tranny not to mention the cost of the driveline modifications.Look around at salvage yards ,2-speed rears are common.

  5. #5
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    You need to find out what the aux. will do. Namely is a low, direct, then with two overdrives, or a double low, low, direct and over. If it only has one low and then direct and overdrive, you aren't really gaining much, because you need to really slow down I'm assuming. The second version would help, but like 25c says, you're going to have driveline issues, as well as mounting, and the worst thing, making the linkage. You can't make the drivelines yourself, because they need to be balanced, and I doubt you have that equipment. Plus you may have to move hangar bearings and such, which means moving the mounts on the frame rail, as well as keeping the angles correct. The two speed rear is a great idea, you can change it yourself, the driveline will bolt right up, and all you have is a cable running to the rear. If you can live with a lower down the road speed, try to find a rear end with a lower gearing. You've got plenty of power with the Cummins, I'm guessing you just would like to crawl around jobsites a little slower, and not have to wind it up so much loaded from uphill stoplights. A slower speed rear would really help this, and if you needed new rear tires, get smaller ones. With just a single axle tractor, you don't need a big 13 or 15/18 sp tranny, and like 25c says, there are a lot of the old 2 sp rear ends around, making your 6 sp actually a 12 sp.

  6. #6
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    The 2-speed rear end is the best way to go.Or a lower geared ratio like a 4.10 or 4.33.Either way dont worry about balancing the driveline.Anyone can make a driveline.I usually cut the driveshaft to length ,then drive the yoke in,and install it in the truck.I block up the rear end so I can spin it in the truck while welding the yoke to the driveshaft.I use a dial indicater to index the driveshaft.If you dont have a dial indicater,Use cribbing under the driveshaft to measure if it's out of round.My point is ,if the driveshaft is centerd on the yoke,it wont vibrate or cause trouble.

  7. #7
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    Auxiliary Transmission:

    Quote Originally Posted by amunderdog View Post
    I are Poor
    Well, I reckon I can relate to that answer, easier than any post I've read on this site...

    And, if you ever find the need... you can use my "poor boy shop pit" any time you want... LOL

    Seems like I've been using the word fairly often myself... LOL...



    Completely understand,

    OCR

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    Not a bad truck, what year is it?

  9. #9
    Senior Member amunderdog's Avatar
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    1993 or 94 Model.
    Spicer 6041 = double low, low, direct and over.
    Ok
    So you all like a two speed rear axle. I do not. They do not split that much. and i think i remember them giving a higher ratio to help overcome lower gearing.
    I already have a 4.10 rear. would have to g to a 5 somthing, then would kill road gear.
    If i had the jack the easiest fix is to swap the trans.
    I was hoping there was a seasoned wrench on here that could help me with the yoke problem. The rest i have about figured out.
    Thanks for the input....................
    Last edited by amunderdog; 05-05-2009 at 07:38 PM.

  10. #10
    Super Moderator willie59's Avatar
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    Quote Originally Posted by amunderdog View Post
    1993 or 94 Model.
    Spicer 6041 = double low, low, direct and over.
    Ok
    So you all like a two speed rear axle. I do not. They do not split that much. and i think i remember them giving a higher ratio to help overcome lower gearing.
    I already have a 4.10 rear. would have to g to a 5 somthing, then would kill road gear.
    If i had the jack the easiest fix is to swap the trans.
    I was hoping there was a seasoned wrench on here that could help me with the yoke problem. The rest i have about figured out.
    Thanks for the input....................

    I don't recall anyone here saying they "liked" the two speed rear. I, instead, read the responses as saying you'd have difficulty fitting a hog box in there on such a short wheel base. That's just the way I was reading it. And for my curiosity, what is "the rest I have about figured out."?
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  11. #11
    Member GaryKelley's Avatar
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    2 spd

    its possible, that you can search around the wrecking yards, and find both of the ends of your main trans and the aux to marry them together, and then you will only have to shorten your driveline, which you are probably going to have to do, regardless of what path you choose. or... you could go to smaller tires, but I doubt that you could downsize enough to gain enough there..

  12. #12
    Senior Member LowBoy's Avatar
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    I'm with the 2 speed rear guys on this one. A lower ratio (5: something's,) will give you the low-low you're looking for, and a pull up on the red button will give you the road speed you'd need I'd imagine. I can't picture you wanting to run down Interstate 40 at mach 1 with the 'ol gal either, so it ought to be about right once you find the proper ratio'd rear.
    If you find a rear somewhere and don't see a tag on the housing to tell what gears it has, simply count the number of teeth on the ring gear, and the ones on the pinion, and divide the little number into the big one (ex: 52 on ring, 12 on pinion, = 4:33).
    Mounting that aux box into that short little wheelbased truck might end up being the "mother of all projects" by the time you're done. Plus, if it already has medium-duty yokes on it, and you're wanting to install it into something that already has 1710 series style yokes for example...there may be a mismatched torque issue here... (in other words, not heavy enough.) Although you'd most likely eliminate the need for a carrier bearing because the distance between the gear boxes and rear won't exceed 60", it's still a chore.
    Even a 'po boy's gonna spend some hard earned money making that work amunderdog.
    I'd rethink your opinion on the 2 speed rear if I was in your shoes. You can find a lot of old dumps, garbage trucks and all kinds of dead iron around farmers fields and salvage yards with the gears you'd need for short money, and for a Saturday's work underneath it, you'll have quite a nice ride when you're done...
    "I can break an ANVIL..."

  13. #13
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    Spicer 6041 hawg box

    I dont know if this will help amunderdog.I pulled out our 1962 gmc 5500 this after noon and took a few pics of the 6041 auxiliary tranny.It measures about 2 feet long between the u-joint flanges.It might fit in your truck.You need the gear shift socket & linkage.The auxiliary gear shift socket will mount on the mainbox.Look around at salvage yards for u-joint yokes and use your imagination and skills to adapt the drive line.Here are some pics.I am only about half seasoned looking forward to well seasoned.
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  14. #14
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    So you can figure out all the other stuff, but need a seasoned mechanic to tell you where to get parts? Everytime I write a reply any further than this I get mean, sarcastic and nasty. hint:truck parts store, driveline shop, salvage yard. Good luck, send pics when you get it done. Ps, nice pics 25c, is the old girl a gasser? bet she grunts full of wet corn! It was a grain hauling king when it was built!

  15. #15
    Senior Member LonestarCobra's Avatar
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    I still have an old Chevrolet truck similar to that my grandad bought new. It is just a tractor, and the old grain trailer is down in our graveyard of tractors and vehicles. It has the 409 gasser in it. It ran 4-5 years ago when I put it in the barn.

    As far as the gearing problem goes, I would also go with the 2 speed rear end. We have a C-70 that has one mean low gear. When the axle is in high, it will run 60 mph comfortably. I really would not want to drive that thing much faster than that.

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