Can someone explain this ?

1968 -1970 Mopars

  1. pearljam724

    pearljam724 Well-Known Member

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    Ive been having slight vibrations in my driveline over 65 mph. I found the problem. If I raise my front end 1.5 inches by turning the lower control arm adjusters the vibration disappears. I shimmed the rear end 2 degrees. The car is slightly raked toward the front. Telling me, my pinion angle needed adjusted.
    I take it for a several mile ride, come back and front end drops back down to where it was previously on its own ? I can crank it back up 1.5” and do this all day long, vibration disappears and then front end drops back down causing driveline to vibrate again, repeatedly ? I’m sure it’s torsion bars related. But, what’s going on here ? Nothing is broken that I can see.
     
    Last edited: Oct 19, 2019
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    • 493 Mike

      493 Mike FBBO Gold Member FBBO Gold Member

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      You have entered the "Twilight Zone".
      Mike
       
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      • dadsbee

        dadsbee FBBO Gold Member FBBO Gold Member

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        Raising and lowering is changing the front end alignment. Pick where you want it to sit and then get it aligned. That or you've lost a wheel weight.. as did I on my Bee thinking my alignment had been done wrong.
         
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        • WP29440SE

          WP29440SE Well-Known Member

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          are you saying you are cranking up both torsion bars and they are magically lowering themselves back to where you started? no way are the adjuster bolts backing out. if the torsion bars were somehow spinning they wouldn't raise the car up in the first place. if they were that weak I'm sure they would have snapped by now. my statement really only applies to one side, because the odds of both sides behaving the same are astronomical.
          THE TWILIGHT ZONE
          it is
           
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          • dadsbee

            dadsbee FBBO Gold Member FBBO Gold Member

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            Missed that.. you've stripped your adjuster bolts by the sounds of it.
             
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            • pearljam724

              pearljam724 Well-Known Member

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              The problem is it drops ride height on its own after its adjusted. It drops down regardless of where it’s set. I need it to raise 1.5 inches. But, it won’t stay there. The rake is creating a bad pinion angle. If I raise the front end 1.5 inches, it fixes the pinion angle and vibration because the tail of the tranny is lowered in conjunction with the rear pinion. But, by the time I return back to my house. This happens, time and tim again ? It lowers on its own. For example: Top/middle of fender well can be at 26 inches from ground. I raise it to 27.5 with lower control arm and it will drop back down to 26 inches by the time I return.
               
              Last edited: Oct 19, 2019
            • dla4567

              dla4567 Well-Known Member

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              472575EF-69F6-418D-BD20-731DA47A2DDE.png
               
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              • WP29440SE

                WP29440SE Well-Known Member

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                I have a pretty substantial rake on my charger, I have done zilch to the pinion angle. I can adjust up and down with the torsion bars all I want and they stay there, no matter how high or low the back is set.
                if you did strip an adjuster bolt ,the chances of stripping both are highly unlikely. BUT , MEASURE how far out each adjuster bolt is after you crank it up , then check them after your ride around the block. that will at least rule that out. make sure they are actually screwing in and not just spinning
                 
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                • 33 IMP

                  33 IMP Well-Known Member

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                  Are you jacking up the front end before you adjust the torsion bars? You have to take the weight off before you adjust . I agree with dadsbee, i think something is stripped.
                   
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                  • 1 Wild R/T

                    1 Wild R/T Well-Known Member

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                    To add to the confusion raising or lowering the front of the car should have no effect on pinion angle...

                    It'll change the angle of the pinion but it won't change pinion angle....

                    Pinion angle is the variation between the angle of the transmission output shaft & the pinion in the differential... When you raise the front of the car the transmission angle changes the same as the rear axle...

                    Now if the front of the car were being lifted by engine torque that would be an entirely different matter cause when the torque is applied to the axle the pinion tries to climb the ring gear so the pinion goes nose up....

                    But simply lifting the nose to the car whether by a jack or cranking up the torsion bars has no effect on pinion angle
                     
                    Last edited: Oct 19, 2019
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                    • beanhead

                      beanhead FBBO Gold Member FBBO Gold Member

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                      And, bounce the the front end real good to settle it before calling it good.

                      Ok true story....back in high school my bud got handed down a '69 dart 340 so we commenced to hot-rodding it. He was like "Cool man it rides stiff! Muscle car!" and I remember saying...dude...there's no front shocks in there. LOL he probably put a couple hundred miles on it like that.
                      Oops!:D
                       
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                      • pearljam724

                        pearljam724 Well-Known Member

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                        I bounced the front end very well after I let it down off the jack to settle the suspension every single time before I remeasured it. . All weight was off the front wheels. I know this sounds crazy. It baffles me too. And yes, I could understand if something was broken on one side making that happen to one side only. But, it does it every single time to both sides ? I’ve done it a dozen times. One side control arm bolt turned easily from the beginning. The other side turned after some PB blaster with fair amount of effort. But, they were both mildly rusty. One bolt is sticking out further at the bottom of control arm than the other close to an inch, even if I measure both fender wells to be at the same height. Something isn’t right obviously, but I dont know what is causing this ?
                        The car isn’t slightly out of alignment. I know this because I put 3k miles on a new set of tires and there isn’t any slightest uneven wear on any of them and it drives straight as an arrow down the road, even with my hands off the steering wheel at all speeds. It tracks straight as can be. No tires squealing turning, etc. Ok, let’s forget about the pinion angle. It still doesn’t explain why the front end is raised 1.5 inches. Take it for a several mile ride and it returns to height before adjustments were made, not touching anything and I’m measuring it in the exact same location parked in my garage ? 1.5 inches raised or lowered is a very substantial amount and is quite noticeable, even with the naked eye. If this makes me crazy. I’ll make a video proving it, lol ! It’s hard for me to believe too. Only conclusion I have is stripped adjuster bolts. But, if that were the case. Why would I easily be able to raise it back up again, time and time again? I ll look at threads tomorrow.
                         
                        Last edited: Oct 20, 2019
                      • BeatersRus

                        BeatersRus Well-Known Member

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                        what kind of front shocks do you have on it?
                        what condition are they in?
                        are they factory style or aftermarket,maybe the reach is too short?
                        (as far as your vibration.)

                        the going back down sounds bad..odd too.
                        did you use air tools or hand tools on the adjusters?
                        it sounds like it has to be pushing the adjusters back out,
                        otherwise you would have cranked the adjusters all the way in by now.
                         
                      • Darter6

                        Darter6 FBBO Gold Member FBBO Gold Member

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                        I'd start looking at the mounting point of the lower control arm into the K frame.Check for cracks where the lower control arm holes are.The lower control arm nut torque tight ? Check for any movement and condition of the bushings.
                         
                      • pearljam724

                        pearljam724 Well-Known Member

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                        I think they are Monroe and probably several years old. There’s nothing wrong with them, no leaks. Vibration is definitely in driveline. I’ve done everything but, have it balanced. I used a 1/2 drive, ratchet.
                         
                      • pearljam724

                        pearljam724 Well-Known Member

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                        I ll put the car in the air and check for wheel slop. But, based on 3k tire wear being absolutely perfect. I don’t think there will be any. Car components never make the slightest noise driving down the road. Except, my rear leaf spring bushings needing replaced. I don’t know the reason, but something isn’t allowing the adjustments to stay in place. Maybe, the torsion bars are have something to do with it ?
                         
                        Last edited: Oct 24, 2019
                      • Darter6

                        Darter6 FBBO Gold Member FBBO Gold Member

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                        T-bars, very doubtful. And remember the advice you get here,we are just shooting in the dark.It's hard when you can't physically see,even sometimes in photos, what is going on.
                         
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                        • pearljam724

                          pearljam724 Well-Known Member

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                          I understand and agree, bud. Thank you
                           
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                          • Moparparts

                            Moparparts FBBO Gold Member FBBO Gold Member

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                            There are 2 different factory lengths of torsion bar adjuster bolts so you may have the short one on one side and the longer one on the other side and that is why one bolt is sticking out further
                             
                          • pearljam724

                            pearljam724 Well-Known Member

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                            Thank you, that’s very good to know. That clears that up. I’m under the car now. Nothing is broke. Threads on adjusters are not stripped the slightest. A little rusty, but fine. They turn easily. This is extremely odd. I’m going to post a video showing what’s going on maybe next weekend. If it’s warm enough here. I can raise the car a thousand times, it will sit at that height for as long as I want. But, within several miles driving it. It drops back down. That tells me it’s losing tension somehow. But, I have no idea why ?
                             
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