1. domdart

    domdart FABO Gold Member FABO Gold Member

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    I raised up the car with ramps under the back tires and stands up front. I checked the angle of the balancer, the drive shaft, and the pinion. Here is what I have. Do I need some shims? Any advice would be appreciated. Thanks FABO. fullsizeoutput_2f.jpeg
     
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    • Locomotion

      Locomotion Well-Known Member

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      If your drawing is accurate, You are way off. I forgot the exact #'s, but the driveshaft coming out of the trans should be ok. But the pinion should be about 3*-6* DOWN. That way under acceleration, the rear end pinion turns up and basically straightens out the driveshaft/rear end union.
       
    • brian6pac

      brian6pac Well-Known Member

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      The trans and diff should be at the same angle.

      Under acceleration the pinion will lift up so you need to be a few degrees down at static position.

      Driveshaft info Mark Williams.jpg
       
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      • brian6pac

        brian6pac Well-Known Member

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        The pinion down depends on how much it lifts under acceleration.
         
      • Locomotion

        Locomotion Well-Known Member

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        Brian, I agree that the trans & rear should be parallel if at all possible. But that's a weird drawing because the pinion centerline is normally below the trans centerline!
         
      • brian6pac

        brian6pac Well-Known Member

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        I think that is a chassis car with big rear tires in the picture. I know it is backwards for a normal car but it is for reference.
         
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        • domdart

          domdart FABO Gold Member FABO Gold Member

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          The car hops violently when I do a burnout. That is why I checked the angles. It is a 68 Dart.
           
        • brian6pac

          brian6pac Well-Known Member

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          The pinion 4 degree up is your problem, if you change it to 2 degree down would probably fix the problem. You might have to go to 4 degree's it all depends on your springs and how much they twist up.
           
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          • Bad Sport

            Bad Sport HALF A BUBBLE OFF Staff Member FABO Gold Member

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            IF I am interpreting the drawing correctly, pinion angle is up. The long line represents the imaginary line from balancer through the crank and beyond? It should be down at rest. I believe as mentioned above 3*to 6* down is correct. I would try 3 and see where that puts you.

            Ideally you want an imaginary line through the pinion that parallels the engine line.
             
          • Ron816

            Ron816 Well-Known Member

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            I had same problem, pinion angle should be down 2-4 degrees
             
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            • 67Dart273

              67Dart273 FABO Gold Member FABO Gold Member

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              Driveshaft is irrelevant except that you do not want the trans and pinion shaft exactly in-line IE "no angle"

              You want those two shafts PARALLEL when under hard acceleration. If the pinion goes up and it usually does from rest to under power, then as said above, you want the pinon down some in relation to the trans, when at rest. "How much up" it will move depends on your suspension. Normall "guess" headroom is somewhere around 2*
               
            • toolmanmike

              toolmanmike FABO MODERATOR Staff Member FABO Gold Member

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              Hey! "Down in the front" LOL (of the pinion)
               
            • domdart

              domdart FABO Gold Member FABO Gold Member

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              A 4 degree leaf spring shim would give me parallel pinion and engine lines. A 6 degree shim would give me a 2 degree down pinion angle. I am thinking I should try the 6 degree shims. I'm looking for as much advice as I can get. Thanks everyone.
               
            • Locomotion

              Locomotion Well-Known Member

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              There is more involved with wheel-hop than just the pinion angle. Weak leaf springs and/or shocks can be the primary factors. I found that the harder a car leaves, the stiffer the rear shocks should be. Leaf springs are wrapping up into an "S" under hard launches, then they are springing back. Stiffer shocks are suppose to control that, basically dampen the springs and the rise & fall of the body in relationship to the rear end. Coordinating the rear suspension parts with the front suspension makes for better weight transfer and traction.

              Gotta watch the shims being used. Too much angle (thickness) can leave little of the locator pins extending into the spring pads.
               
            • toolmanmike

              toolmanmike FABO MODERATOR Staff Member FABO Gold Member

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              What springs are you running? New, originals, Super Stock?
               
            • TheGrateRonzini

              TheGrateRonzini FABO Gold Member FABO Gold Member

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              I just did an 8.8. I used two cinder blocks, flipped it pad up. Angle finder on yoke. The 7.25 that came out was 5* with the pads level. Replicated on 8.8.
               
            • Bad Sport

              Bad Sport HALF A BUBBLE OFF Staff Member FABO Gold Member

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              That might be a bit much.

              More info on springs, are you running shackles for lift in the rear of the spring?
               
            • 67dartgtgo

              67dartgtgo FABO Gold Member FABO Gold Member

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            • CudaFactHackJob

              CudaFactHackJob FABO Gold Member FABO Gold Member

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              I'd go 1-2 down and add some slapper bars.
               
            • domdart

              domdart FABO Gold Member FABO Gold Member

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              I am running 3 year old ESPO springs with 1or 2 inch lift (don't remember for sure).
               
            • domdart

              domdart FABO Gold Member FABO Gold Member

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              Stock shackles (3 years old)
               
            • toolmanmike

              toolmanmike FABO MODERATOR Staff Member FABO Gold Member

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              So they are fairly stiff (because they aren't worn out) How hard do you launch? Street car, street strip car, strip car? Just wondering if 1-2° is enough. It should be for general purpose stuff. But if you are side stepping the clutch at 6,000 r's or have a auto with a trans brake 2° might be ok as long as you have some kind of traction control. I am curious as to the racing suspension books recommend? (if you have a race car)
               
            • domdart

              domdart FABO Gold Member FABO Gold Member

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              It is a street car with a built up 340, probably around 375 or 400 hp. I put a sure grip 3:55 in it and tried some burnouts. It is a 4 speed. It hopped so much that my z-bar began scraping against my headers.
               
            • Locomotion

              Locomotion Well-Known Member

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              Try stiffer shocks and perhaps add more clamps on the front 1/2 if you have tire clearance.

              Rancho has some 9-way adjustable shocks that have been popular in drag cars. But I don't recall the numbers off hand. You'd have to check the compressed and extended lengths to make sure they are compatible as well as the mounting bushing size..
               
            • brian6pac

              brian6pac Well-Known Member

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              Put a adjustable pinion snubber on it.

              It is all you need on the street.
               
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