Please help with ongoing driveline vibration noise

Engine, Trans & Driveline

  1. HotRod777

    HotRod777 Well-Known Member

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    Hello all. I’ve read hundreds of threads here on BB’s and no one has had my exact issue. I’ve thrown thousands of dollars at this problem (outlined below) and have not gained a penny’s worth of improvement. ANY ideas and welcome. Thank you in advance and sorry for the long read.
    1966 Coronet 383/727.
    I have a “whirling” / vibration noise in the driveline at around 40mph. The most important detail is that it is not there at all under load or under deceleration... it’s right at that “float / cruise” point when the engine is matching the road speed and things relax.
    Here is a list of what I have done/changed that has NOT worked or even affected the noise:
    Tried a completely different set of tires/wheels.
    New green bearings installed, no thrust block.
    Different 742 case with brand new power-loc, new Yukon 3.91, new Timkin master kit.
    Axles slide in easily, no indication of a bent housing.
    Driveshaft- new joints, spun balanced/checked twice by 2 different shops.
    New driveshaft 7260 yoke from Brewers with new tail shaft bushing.
    Transmission is 3° down and pinion is @ 0°.
    I’ve tried 2° and 4° shims both ways (making the pinion -4,-2,+2,+4), no help.
    Checked the converter bolts.
    In neutral, slowly sweeping rpms up and down to 4000 yield no shakes or vibration or the noise... it’s somewhere from the center of the transmission back.

    I have 2 ideas left. I might try to the get tail housing off (might be hard with the TTI H pipe... but I am thinking maybe the tail shaft ball bearing? The one that the C clip holds? The other thing that I keep going back to is the even with the new yoke and bushing from Brewers the yoke has a lot of play. With the driveshaft installed I can “clunk” the yoke up and down in the tail housing. That is with the brand new yoke and bushing. This has bothered me from the beginning but how could it be wrong being it’s all brand new? The bushing drove in very snug as expected.
    I’m lost.....
     
  2. 66 Sat

    66 Sat Well-Known Member

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    It could be a harmonic not directly related to the drivetrain e.g. at that speed the exhaust vibrates against a leaf spring. Very hard to track down (as you've discovered). Get under the car and check absolutely everything is tight or has good clearance e.g. exhaust, rear shocks, leaf springs, parking brake cable adjuster, seat mounts etc. It might be something simple.
    Does it do at 40 mph in any gear?
     
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    • khryslerkid

      khryslerkid FBBO Gold Member FBBO Gold Member

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      How much up and down in the tail shaft/yoke? How much yoke shaft is showing when the car is on the ground?
       
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      • Fran Blacker

        Fran Blacker FBBO Gold Member FBBO Gold Member

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        Tailshaft should have bushing. Mine rattled. If you pull bushing this is the tool you need so you don't have to pull tailshaft. Looked on ebay for it under trans tools, no luck but they could be there. Cost $75 to $135. nice to get install tool with it. transt.jpg
         
      • Fran Blacker

        Fran Blacker FBBO Gold Member FBBO Gold Member

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      • #41

        #41 Well-Known Member

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        Its actually supposed to have a little play even with everything fresh.
         
      • turbine68rt

        turbine68rt FBBO Gold Member FBBO Gold Member

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        Be sure to properly index the oil feed hole with the groove in the extension housing when installing the new bushing.
         
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        • moparmarks

          moparmarks FBBO Gold Member FBBO Gold Member

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          I think your pinion angle is backwards. Tranny should be at 0* and the diff should be down 2-4*
           
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          • Don selleck

            Don selleck FBBO Gold Member FBBO Gold Member

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            my vote is pinion angle, rear end moves out of range under load.
             
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            • HotRod777

              HotRod777 Well-Known Member

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              I’m using the long seal so if you ignore it I have about 2” exposed if measured from the traditional seal point.

              That is the same tool I bought and used.

              Oil hole was centered correctly at 12 o’clock.

              I suppose I could put an additional shim under the mount (or thicker, there was one already one under the mount).

              Has anyone ever had the rear bearing, the one that the C clip clips go bad?

              Thanks for all the replies so far. Please keep any and all idea coming.
               
            • turbine68rt

              turbine68rt FBBO Gold Member FBBO Gold Member

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              Might be a factor

              20201127_102721.jpg
               
            • Mick56

              Mick56 Well-Known Member

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              I think the front and rear u-joint angles should be the same. There are many u-tube videos showing how to set up driveline angles., and making sure the rear end is set up square in the car.
               
            • Fran Blacker

              Fran Blacker FBBO Gold Member FBBO Gold Member

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              I had a short d shaft that killed the bushing. There was .012 clearance between bushing and yoke. This is what I have now (see pic weigh on wheels) with the length d shaft SM calls for. Have a d shaft 1" longer also, looked long when installed.
              DS7.JPG
               
            • HotRod777

              HotRod777 Well-Known Member

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              With the weight on the wheels I have almost exactly what you show in your pic, about 2” exposed from the seal flange. Is the pic a pic of when you had the problem or is it a pic of the longer
              driveshaft?
               
            • turbine68rt

              turbine68rt FBBO Gold Member FBBO Gold Member

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              See post 11. With the long boot seal like you have, there shouldn't be more than 3/4" of the shaft exposed from the end of the seal.
               
            • Fran Blacker

              Fran Blacker FBBO Gold Member FBBO Gold Member

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              Had 68 GTX with a Dana 60 d shaft in which caused the problem 1" shorter than picture. http://www.mymopar.com/index.php?pid=31
              Download a manual for your car and look in prop shafts this what you'll find. ddl.JPG
               
            • Slap Stick

              Slap Stick Well-Known Member

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              Believe it or not a sloppy timing chain will do the same thing.
               
            • dvw

              dvw Well-Known Member

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              Is this really a vibration? Or just a noise? To me if it’s just noise sounds like ring and pinion. There is nothing the matter with your pinion angle. There is a difference of 3 degrees and it’s in the proper orientation.
              Doug
               
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              • biomedtechguy

                biomedtechguy Accelerati Rapidus Maximus FBBO Gold Member

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                I had a 8 3/4" driveshaft in my 70 440 6bbl Dana 60 car. That little bit too short of driveshaft length made it vibrate at highway speed. So...
                Look at pinion angle recommendations, load on the driveshaft will make it pivot upwards at the rear U joint.
                Forgive the following:
                Don't do 40
                Get a louder exhaust
                Turn up the radio...
                Good luck, you're in the right place.
                 
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                • HotRod777

                  HotRod777 Well-Known Member

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                  I checked again with the weight on the car. My yoke is exactly like yours, 2” from the seal flange to the big part of the yoke.

                  My shaft is stock, I measure 52-1/4 which matches the chart. It has the tone ring weight and the rear necks down slightly to meet the small 7260 yoke. It was spun balanced by 2 shops, both said its perfect.

                  The 383 is rebuilt in 2019 and has a 9 keyway Cloyes timing chain, I “hope” that’s not the problem.

                  I’m using the current style green bearings that use the c clip ring that sets the depth. I was told by my ‘reputable’ driveline guy that it didn’t matter if the thrust block was in the center section. Is this correct? Obviously it’s needed with tapered bearing. He said they only needed removed when going to the early, original-style green bearings that did not have the c clips. I’m just grasping for any possible causes.
                   
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