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Technical Another pinion angle question

Discussion in 'The Hokey Ass Message Board' started by demon452, Sep 20, 2020.

  1. demon452
    Joined: Dec 23, 2007
    Posts: 380

    demon452
    Member
    from Michigan

    20200920_073009.jpg Ok the terminology confuses me. I found this chart and circled how my transmission and pinion angle are at. I have a triangulated 4 link with rubber bushings. My transmission is roughly 1 1/2" higher than my rearend if that plays any part.

    Anyhow my transmission is 4 degrees (per chart) and I have no way to (lift) up and decrease the angle. Pretty damn close to trans tunnel.

    My pinion per the chart is at 3 degrees, if trying to tilt up and achieve a matching 4 degrees I may not have the floor clearance.

    Anyhow I am asking if this will work being 1 degree out? Or will i get premature wear on the u joints?

    Also I am confused on the bottom half of the chart. Why is center diagram on upper and lower sections completely different on the pinion side? Is that based on if the rearend sits higher than the transmission?

    Yes I noticed the chart says 4 link and ladder bar.

    Thanks in advance
     
    Last edited: Sep 20, 2020
  2. demon452
    Joined: Dec 23, 2007
    Posts: 380

    demon452
    Member
    from Michigan

  3. dcs13
    Joined: Sep 28, 2010
    Posts: 109

    dcs13
    Member

    3 down (trans) 3 up (pinion) is pretty good for a street car. 4 is no big deal. Don't sweat it.
     
  4. demon452
    Joined: Dec 23, 2007
    Posts: 380

    demon452
    Member
    from Michigan

    I didnt think 1 degree would matter. Everything I have been reading states 1 degree is acceptable.

    Just overthinking I suppose.

    So what is the bottom half of the chart referring to? The pinion is opposite of what i have circled. Meaning why is the pinion down not up?

    Thanks again
     

  5. kabinenroller
    Joined: Jan 26, 2012
    Posts: 518

    kabinenroller
    Member

    neilswheels and okiedokie like this.
  6. demon452
    Joined: Dec 23, 2007
    Posts: 380

    demon452
    Member
    from Michigan

    Haha, yes I found that yesterday. According to the app its says acceptable. Well all green anyways.
     
  7. Joe H
    Joined: Feb 10, 2008
    Posts: 945

    Joe H
    Member

    Bottom of chart shows pinion down since engine is up, no different then what you have just opposite direction. The driveline doesn't know the difference.

    Remember, you are just setting the baseline, when driving or racing, the angle is constantly changing and will be all over the place angle wise. One or even two degrees over or under the " ideal angles " will not hurt a thing, just be sure you setting up with the full " as driven " weight on the axles, that includes driver and passenger weights.
     
  8. demon452
    Joined: Dec 23, 2007
    Posts: 380

    demon452
    Member
    from Michigan

    This is the diagram I was referring to. I do understand when the engine is tilted (front) the opposite goes for pinion. But these I have circled both arrows are down. 20200920_104054.jpg
     
  9. Almostdone
    Joined: Dec 19, 2019
    Posts: 309

    Almostdone
    Member

    If I get your question correctly, what you are seeing in your chart is a slight preload to counteract the rise in the pinion under acceleration. I didn’t know it differed between 4-link and ladder bars.
     
  10. patterg2003
    Joined: Sep 21, 2014
    Posts: 620

    patterg2003

  11. demon452
    Joined: Dec 23, 2007
    Posts: 380

    demon452
    Member
    from Michigan


    That makes sense. Just didnt realize it would change. know with leaf springs its totally different as well.
     
  12. demon452
    Joined: Dec 23, 2007
    Posts: 380

    demon452
    Member
    from Michigan

  13. ekimneirbo
    Joined: Apr 29, 2017
    Posts: 1,441

    ekimneirbo
    Member
    from Brooks Ky

    Think of it like this. You DO NOT want the trans mission angle and the rear pinion to be in a direct line (even if trans is down and pinion is up). Generally about 3 degrees down for the trans and 3 degrees up for the pinion BUT in different planes. Most of the time the pinion will be in a lower location, so if you extended the line out from the pinion it would pass below where the front u-joint is located......but be close to parallel with a line from the trans u joint.
    Basically parallel planes on similar angles.
    Now with leaf springs moving up and down thats going to vary some when driving, and thats good. Also if you accelerate hard, the springs will tend to let the rear end rotate and change the pinion angle a little (lot). For that reason its good to actually keep the pinion on slightly less than the 3 degree angle....more parallel to the ground. Then the normal reaction of the rear end as torque is applied for general driving is to rotate the pinion up to the desired 3 degrees. You can't check it very easily, so you just go a degree or two down and it will rotate slightly upward as you drive. Thats when using leaf springs.
    If you use a four link, the rear end pinion can move up and down when the car is in motion, but it can't rotate like it can with leaf springs.
    This video isn't exactly applicable, but you get the idea of whats happening.
     
  14. getow
    Joined: May 9, 2016
    Posts: 56

    getow

    Hey thanks to who ever posted that Spicer thread info. Ive had some trouble sorting out a 2 piece shaft ongoing issue. That info helped to make it more understandable.
     
  15. neilswheels
    Joined: Aug 26, 2006
    Posts: 815

    neilswheels
    Member
    from England

    I’ve got that vibration On my Ranchero that the Hot Rod article mentions, someone swapped in an 8.8 rear, guess I need to check those angles.

    How do you adjust the pinion angle on a transverse leaf rear end? Need to check my 40 as well...
     
  16. The Shift Wizard
    Joined: Jan 10, 2017
    Posts: 2,089

    The Shift Wizard
    ALLIANCE MEMBER

    Just focus on the left and middle columns. Ignore the right column unless you have a 4-link or ladder bar.
    I repeat; Pay no attention to the right columns. Don't circle anything there. Don't look at it. It's not for you. :p
    One degree difference is not too bad in your circumstance. At least the slope at each end is going the same way. U-joints can speed up and slow down in a single rotation so having the slope the same keeps them in phase and not fighting against each other by each end trying to speed up at different points in a rotation.
     

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