727 tailshaft loose

Engine, Trans & Driveline

  1. Babyblue66

    Babyblue66 Well-Known Member

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    Never mind. This is pointless.
     
    Last edited: Apr 24, 2021
  2. #41

    #41 Well-Known Member

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    The bushing is not supposed to be a part where the yoke rides against it. The spines on the trans output shaft are designed to lock up with the spines on the yoke when under power and the yoke should not engage the bushing at all. If your situation is such that the yoke rides against the bushing, you will burn it up.

    The fact that you have bought three different bushings and they are all the same would indicate something. I would be looking at that new yoke or elsewhere. Good luck.
     
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    • AR67GTX

      AR67GTX Well-Known Member

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      Also the bushing will shrink one to two thousands in dia. when it’s driven into the tail housing so you need to allow for that. Have you checked how much play the new yoke has in the loose bushing with a feeler gauge?
       
    • R413

      R413 Well-Known Member

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      Agree with this, checking the fit with a loose bushing is of no value. It’s going to get tighter when installed.
       
    • Fran Blacker

      Fran Blacker FBBO Gold Member FBBO Gold Member

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      After I installed a new bushing driveshalft didn't slide in, took some pushing.
       
    • AR67GTX

      AR67GTX Well-Known Member

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      If it’s installed then .004 clearance is a little loose. I think probably around .002 to .003 is about what you should expect normally. Sometimes in driving a bushing in, the end can get mushroomed slightly and the yoke can almost be an interference fit and be tight initially or in extreme cases require reaming before the yoke will slide in. Can you mic or caliper the yoke diameter and post it?

      Have you actually trial-assembled the tail housing to the transmission and tried installing the yoke? Seems I remember mine feeling a bit loose until I assembled everything and then the yoke seemed to be snug with no play once slid over the splined output shaft.
       
      Last edited: Apr 24, 2021
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      • pnora

        pnora FBBO Gold Member FBBO Gold Member

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        Are you sure the slip yoke is going in deep enough? At ride height the yoke should be out no more than an inch. If the yoke is out it will be loose.
         
      • 440 Charger

        440 Charger FBBO Gold Member FBBO Gold Member

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        Never.
         
      • pnora

        pnora FBBO Gold Member FBBO Gold Member

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        So at ride height suspension loaded take the driveshaft loose and push it in as far as it will go. Mark it and bolt it back up. Measure the difference. My bets you are missing the boat on blaming the bushings. Measure like I said and report back.
         
      • pnora

        pnora FBBO Gold Member FBBO Gold Member

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        Do not be lazy and do not be stupid. Measure and tell us how much the yoke pulls out. You have tried different yokes, bushings and tail housings. You missed it sorry.
         
      • pnora

        pnora FBBO Gold Member FBBO Gold Member

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        Ok you win. I am done.
         
      • Fran Blacker

        Fran Blacker FBBO Gold Member FBBO Gold Member

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        Here's a picture of my d shaft. The trans shaft comes an 1' or so out of tailshaft housing. Which means trans shaft is at the 1" line on tape measure. So you have 1" of splines in d shaft left. At 2" mark machined part of yoke ends. Have short seal on trans. DS1.jpg
         
      • #41

        #41 Well-Known Member

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        I don't think that the engineers that design these have had it all wrong for 100 years. It's the splines between the trans output shaft and the yoke that do the work. The bushing is secondary.

        If your yoke wobbles so much that it must rely on a tighter bushing clearance to restrict movement enough to eliminate vibration, you have other problem causing an imbalance in the first place. Look for that to solve your vibration.

        Or just keep replacing bushings.
         
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        • Fran Blacker

          Fran Blacker FBBO Gold Member FBBO Gold Member

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          If you have .003 or .004 yoke to bushing don't think it will rattle. Had .013 on mine rattled at 3200 rpm.
           
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          • AR67GTX

            AR67GTX Well-Known Member

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            The shaft and rear ball bearing are definitely not enough alone to rigidly locate the yoke way out at the end of the shaft. A proper fitting bushing and yoke that has not worn down are absolutely necessary to prevent play and driveline vibration. The yoke may fit tightly on the splined shaft but a loose bushing fit will allow the whole thing to whip around like mad at speed, especially once the driveshaft gets up to speed.
             
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            • 4406bbl

              4406bbl Well-Known Member

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              The bushing is the primary. The factory installed the bushing, then reamed it to size. That is why they last so long. I have never seen the exact spec for bushing to yoke clearance. The current brass bushings are a little looser than the the old mopar babbit ones I used. The last neapco yoke I had was a .0005 small. The yoke should be bottomed and pulled out 1", if you have the extended dust seal it barely cleared the yoke at full load ride height. Anyway it is hard to get to .002 clearance with new bushings, I had my yoke hard chromed to get it tighter. You results will vary, but the fact the bushing is primary is fact.
               
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              • 4406bbl

                4406bbl Well-Known Member

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                This yoke is from an untouched before me 1970 roadrunner dana car, I have 3 of these driveshafts, all pattern the same within 1/16". Pic shows where the dust seal rode on the yoke, center mark is where the lip of the dust seal rode the most.

                16193656405091703996579.jpg
                 
              • Babyblue66

                Babyblue66 Well-Known Member

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                If they did ream the bushing to size, how do we get a tight fit since all bushings I've tried seem too loose in my opinion?
                 
              • 4406bbl

                4406bbl Well-Known Member

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                I do not have a good answer. As others have said the bushings do tighten up once they are installed if you are just trying a loose bushing on a yoke.
                 
              • Babyblue66

                Babyblue66 Well-Known Member

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                No, these are installed.
                 
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