1. TripleL

    TripleL Active Member

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    Why is the pinion angle so critical on these cars while say a 4x4 can have alot more angle with no vibration
     
  2. SplangJ

    SplangJ FABO Gold Member FABO Gold Member

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    I think if the car’s stance is close to original, it’s close enough. See how it rides, and if it vibrates try shimming the axle up or down a tad and run again. I’ve been in cars with the ass end obnoxiously high, and didn’t notice any vibration.
     
  3. Treblig

    Treblig FABO Gold Member FABO Gold Member

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    The angle of the driveshaft (4 X 4s) doesn't hardly matter at all. What matters is the angle of the engine crankshaft/trans relative to the rear end pinion angle.....WATCH:

     
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    • Treblig

      Treblig FABO Gold Member FABO Gold Member

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      Here's more:

       
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      • SplangJ

        SplangJ FABO Gold Member FABO Gold Member

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        THAT was quite an example, hard to wrap my head around it. I just assumed all parts would be moving equally. So on a lifted 4x4, with an extreme driveshaft angle, all is well if the rear end yoke and tranny are in line?
         
      • Treblig

        Treblig FABO Gold Member FABO Gold Member

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        Well you're close............??? Normally the angles (engine and yoke) are set so that when there is a load on the drive train (during acceleration) the tranny and yoke are at the same angle. So if you set your pinion angle with the car sitting still (static) you need to have the yoke about 2 1/2 degrees down relative to the engine/tranny angle. Now other people might say 2 degrees and some might say 3 degrees ....to each his own. The point is that when you accelerate the pinion yoke will rise up a degree or 2 at which time it will be at the same angle as the engine/tranny. Make sense??
         
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        • SplangJ

          SplangJ FABO Gold Member FABO Gold Member

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          Yes! You would really notice any vibration while cruising, but not notice necessarily while under WOT. Great post Treblig!
           
        • Treblig

          Treblig FABO Gold Member FABO Gold Member

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          Remember, when you hit the gas the rear end (yoke) will rotate up (changing the pinion angle). The type of rear suspension (loose or tight) will determine how much the pinion needs to be pointed down relative the engine/trans angle.......Here's another explanation:

          pinionangle-1pcshaft-jpg.jpg
           
        • Treblig

          Treblig FABO Gold Member FABO Gold Member

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          Thanks...there is a "HAPPY PLACE" for the pinion yoke as demonstrated by all factory cars (no vibration at all). That's why they invented pinion angle shims for us hot rodders!!!!
           
        • SplangJ

          SplangJ FABO Gold Member FABO Gold Member

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          Surely. With a snug pinion snubber you might see some housing twist at launch, but settles back down with less torque at speed, leading towards no vibration at all, like cruising. No one will notice a driveshaft imbalance at low driveshaft speed for a few seconds
           
        • 67Dart273

          67Dart273 FABO Gold Member FABO Gold Member

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          That video is excellent. The "simple story" is that with a common 1 piece shaft like A bodies use, the two end shafts (trans and pinion) MUST BE PARALLEL under load. You will find a 4x4 does the same thing. The shaft speeds up and slows down every 1/4 turn, and that is cancelled at the "other end" IF THE angle is the same at both ends.

          You can "feel this" for yourself with a socket drive U joint.
           
        • TripleL

          TripleL Active Member

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          Thanks for the great info. Thats just one reason I'm not designing cars.
           
        • pishta

          pishta I know I'm right....

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          Thats why they created the CV joint "constant velocity" for the FWD half shafts.
           
        • fishy68

          fishy68 Tyr Fryr's Inc. FABO Gold Member

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          Excellent video
           
        • TripleL

          TripleL Active Member

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          My 3 point post hole digger does the thump and bump at certain angles when drilling so same concept. Learn something every day
           
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