Vibration right off idle

Transmission and Drivetrain Tech

  1. plumkrazee70

    plumkrazee70 Well-Known Member

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    The engine, while relatively new has been run with the 904 behind it for a very short time. This can't be. Misfire. I can feel it in my seat.
     
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    • George Jets

      George Jets 1967 Dart 2 Door FABO Gold Member

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      OK if you can feel it in your seat, that is telling you that the transmission is making contact with the tunnel and transfering the vibration through the floor up to your seat.

      Yes, scratch the misfire then.
       
    • Phreakish

      Phreakish Well-Known Member

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      That's good info to have. At least you know it ran right before the swap.
       
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      • plumkrazee70

        plumkrazee70 Well-Known Member

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        I'm gonna put it up high on stands tonight after work and check it out.
         
      • CudaFactHackJob

        CudaFactHackJob FABO Gold Member FABO Gold Member

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        Does it vibrate driving with the engine shut off?
         
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        • plumkrazee70

          plumkrazee70 Well-Known Member

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          I haven't tried that yet. I did read that as a place to look when I was researching last night.
           
        • plumkrazee70

          plumkrazee70 Well-Known Member

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          Ok, so I think I got the vibration off idle, fixed. I looked all around the trans and all was good, but I noticed that my driver's header was touching the torsion bar. So I used a pry bar and put a wood shim in there and tested it on stands and it appears that noise vibration is gone. So I need to fix that. While doing so I noticed that I have two different motor mounts (rubber) so I need to fix that and level the engine and retest. Ugh... I created a new thread in the SB engine section seeking help to confirm what I need.
           
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          • 512Stroker

            512Stroker We are all here because we are not all there.

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            While you are under there, if possible, take the torque convertor bolts out rotate the convertor 180 degrees and reapply the bolts.
            See if that changes your vibration
             
          • Brooks James

            Brooks James Dustoff

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            What’s the story on the harmonic balancer??
             
          • plumkrazee70

            plumkrazee70 Well-Known Member

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            Good idea. I did check the torque.
             
          • plumkrazee70

            plumkrazee70 Well-Known Member

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            It's new and I checked the timing and it's still good.
             
          • CudaFactHackJob

            CudaFactHackJob FABO Gold Member FABO Gold Member

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            I'm just staying in here for the laffs at this point..
             
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            • plumkrazee70

              plumkrazee70 Well-Known Member

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              Laffs? You mean laughs? Was something funny?
               
            • CudaFactHackJob

              CudaFactHackJob FABO Gold Member FABO Gold Member

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              Not yet..I'm waiting for you to turn that converter 180 degrees..lol..or should that be haha?
               
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              • 512Stroker

                512Stroker We are all here because we are not all there.

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                Dont laugh to hard partner.
                I personnel saw rotating the convertor cure a vibration on a $120K street rod.
                I know theoretically it should not work, but, it does not cost any $ to give it a try.
                 
              • CudaFactHackJob

                CudaFactHackJob FABO Gold Member FABO Gold Member

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                Ok then, I'll hold my breath starting right now...lmk when you get those last two bolts to go in..
                 
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                • 512Stroker

                  512Stroker We are all here because we are not all there.

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                  Well you may be right.
                  I know on my 727 there is one offset hole.
                  Not sure what they do on the OP's setup
                  The street Rod had a GM system
                   
                • plumkrazee70

                  plumkrazee70 Well-Known Member

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                  I gotcha now. I can't remember if the A500 had an offset hole or not. It's the same plate as the 904.

                  I have to sort out my motor mount situation and go from there.
                   
                • CudaFactHackJob

                  CudaFactHackJob FABO Gold Member FABO Gold Member

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                  Ya, they're all offset...sorry for pickin on you guys...too much Monster..
                   
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                  • plumkrazee70

                    plumkrazee70 Well-Known Member

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                    Ok, so I got new biscuit rubber mounts and the motor is sitting level side to side and so is the trans.

                    I wanted to get your guys opinion on where to measure for pinion angle? For the transmission, I've measured on the pan rail and the end of the tail shaft and I get two different angles. Same goes for the pinon, I measured on the bottom flat, and also the flat of the yoke. Once again two different angles.

                    If I go by the trans tail shaft I get DOWN 2.5* and the flat bottom of the pinion is DOWN 3.9* I used the Tremec App and it will only go green if the pinion is at a max of 3* DOWN.

                    What I don't understand, is all I read is that the pinon needs to be parallel with the trans under load. To be parallel wouldn't the pinon need to be at 2.5* Up under load?
                     
                  • 512Stroker

                    512Stroker We are all here because we are not all there.

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                    Then only place to measure the tranny angle is the tail shaft. Likewise the only place is the pinion yoke for the rearend.
                    You are correct the trans must be tipped up (positive), rearend tipped down (negative).
                    I set mine so they are as close to same angel (-/+) so the tranny and the rearend are parallel.
                    Sounds like you have a bum transmissiom mount.
                    I had to shim both to get it correct.
                     
                  • plumkrazee70

                    plumkrazee70 Well-Known Member

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                    Thank you. I'll re measure at the pinion yoke tonight, to confirm measurements. I have an A500 so it's not stock, but the mount is new.

                    I'll see if I can shim the trans up. When you say you had both angles the same +/- (trans up, pinion down) was that at rest or calculating the pinion rising x degrees under load?
                     
                  • George Jets

                    George Jets 1967 Dart 2 Door FABO Gold Member

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                    3° down at the rear end pinion angle as compared to the tailshaft angle sounds correct if memory serves me.

                    3° down under load comes up to 0° when you put the power too it and get on it.

                    Bump stop above the rear yoke is a safety stop to keep the rear angle from twisting up to high under load and taking the rear u-joint out.

                    Been a long time ago in the 80s when we were setting up new length drive shafts for extending frames and sleepers for semi-tractors, those were set at 1.5° down.

                    In my opinion, double check some more info and or call a driveshaft shop.

                    Good Luck

                    You don't want those driveshaft angles fighting each other. Kind of like some old PTO driven farm machinery when you turn too tight, the u-joints start rattling to beat heck, and is extremely hard on the u-joints.
                     
                  • 512Stroker

                    512Stroker We are all here because we are not all there.

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                    At rest on my 4 post lift with the weight of the car on all 4 tires.
                    Try to keep the angles between 2-2.5 degrees and you should be good to go.
                     
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                    • George Jets

                      George Jets 1967 Dart 2 Door FABO Gold Member

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                      Yes ^^^^^ with the weight of the car on the 4 tires, not free hanging rear end in the air.
                       
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