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Thread: Willys Truck Front PTO Winch Drive Line

  1. #1
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    Willys Truck Front PTO Winch Drive Line

    I'm working on a Willys truck with the Koenig Model 40 twin stick PTO, Koenig Model 100 winch, and the rear PTO drum belt drive. I have all the parts except for the front PTO drive line, that which connects the PTO to the winch. I think I will need to make one up and I was wonder if it is a two piece drive line like the rear is, or is it only a single piece? Thanks for any help.

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    Super Moderator bmorgil's Avatar
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    dg, I am pretty sure they used the "Detroit Style" plunging joint. It is similar to the Bendix style that was used in the early front axles. The same type used in the Willys truck main driveshaft. LarrBeard has great experience with those types of driveshafts. In any event the best bet is to use a standard "Slip Between Center" 2 piece driveshaft and u-joints. Use at least 2 1/2 inch diameter tubing.
    Last edited by bmorgil; 01-27-2023 at 07:16 PM.

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    Super Moderator LarrBeard's Avatar
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    What is the basic year of the truck - and post us some pictures. It sounds like a pretty nicely tricked out Jeep.

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    Guys: The truck is a work in progress and I am still collecting parts, but I did find a picture showing a Willys truck with both the front and rear pto and drives. The picture looks to me to show a 1 piece front driveline? Thanks.

    Willys Truck PTO Picture.jpg

  5. #5
    Super Moderator bmorgil's Avatar
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    That is correct dg, the Detroit Plunging Style drivehaft is one piece. You will need to make an adapter to a standard Spicer style flange, and use a standard slip between center driveshaft with flanges on each end.

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    Thanks what I was thinking. The Koenig Model 40 front output shaft is 1 inch with a 1/4 inch keyway, and the Koenig Model 100 winch output shaft is 7/8 inch with a 3/16 inch keyway. I can find both size yokes, and than two receiving yokes one with a slip yoke and the other one not, with the same size shaft opening to connect the front part and the rear part together. Does this sound right? Thanks.
    Last edited by dgoodenow; 01-29-2023 at 07:47 PM.

  7. #7
    Super Moderator bmorgil's Avatar
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    I think you have it dg. You need to hook up to the input and output shafts and then mate those to a slip yoke/tube shaft on one end and a tube yoke on the other end. There are a few P.T.O. shops that are around that could probably fix you right up. The most important thing is the diameter of the driveshaft. As I stated before and cannot state it enough, do not use small diameter tubing. You will need at least 2 1/2" diameter tubing depending on the shaft RPM and length of the shaft. Use too small of a diameter tubing and the shaft will fly out at high RPM do to a phenomenon known as "Critical Speed".
    Last edited by bmorgil; 01-30-2023 at 06:32 AM.

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    Super Moderator LarrBeard's Avatar
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    "shaft will fly out at high RPM do to a phenomenon known as "Critical Speed".

    And I suspect that phenomenon is something to avoid. Tell us more about that Doc Dana.

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    I thought the rear pto shafts were tube, see attached, but the front pto shafts were solid rod, especially the end with the splines that fit into the slip yoke?

    IMG_3394.jpg

  10. #10
    Super Moderator bmorgil's Avatar
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    The shafts you have pictured are not solid. The shafts change length by "Plunging" the joint itself which is on rollers that move in and out in the large outer plunging case or "Bell".
    driveshaft.jpg

    There is some solid, very short shafting involved at the ends. The bulk of the shaft is tubing however.

    "Critical Speed" is a phenomenon that occurs when a driveshaft RPM exceeds the capability of the driveshaft to stay in a straight line. As RPM increases the driveshaft begins to deflect in the center. Picture a Jump rope. The faster you spin it the more it bends in the middle. The heavier it is the quicker it bends in the middle and so on. With a driveshaft there are a few factors involved but for this conversation and the safety of all, driveshaft tube diameter and thickness vs length and RPM are some of the things critical to the equation. In general, the longer a driveshaft is the more diameter that is required in the tubing. Heavy or thicker isn't better and will lower the critical speed because of weight and that "Equation" we spoke of. Solid shafting has a very low critical speed and must be kept to minimum lengths. Arbitrarily selecting driveshaft material, size and diameter has and will kill someone.

    Contact Fort Wayne Clutch & Driveline https://fortwayneclutch.com/product/...u-1310_plycam/ for a conversion shaft. They are in LarrBeard's neck of the woods. I think Larry may have already spoken to them about converting the plunging shaft on his Willys.
    Last edited by bmorgil; 01-30-2023 at 06:37 PM.

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