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Technical Pinion angle: there’s no 4th rule.

Discussion in 'The Hokey Ass Message Board' started by 31Vicky with a hemi, Sep 20, 2023.

  1. The fourth rule,,,
    Undoubtably and understandably, you’ve encountered this imposter 4th rule. It’s hard to ignore but worth the effort. Since this fourth rule is so established, you’re probably not even aware of it. How it came to be I am unsure. Nothing better for you and your drive line to ignore it completely.

    There’s a whole bunch of basic ground rules before getting to these 3 rules. Your situation will differ slightly from the next guy and those are basically established ride height and operating weight, setting up on relatively level surfaces and having some decent equipment and measurements. It’s all basic stuff but different ways to achieve it. Those aren’t what I’m getting into.

    Each rule is based on the one prior beginning with level at ride height then rule #1. No rules violate each other, ever. That’s why they are rules. You can find the 3 rules on any driveline site, be careful to spot rule 4 even there. I’ll do my best to help you spot this 4th rule but I can’t help you ignore it though it’s best that you should.

    The first rule is “everything viewed from the transmission to the rear”. ((( the term everything means everything )))

    The second rule is - down slope (rule 1) are negative and up slope ( rule 1) are positive. ((( up and Down hasn’t been changed)))

    The third rule is math “ when the slopes are both (rule 1&2) negative - subtract the smaller from the larger, when both slopes are both (rule 1&2) positive you subtract the larger from the smaller , if slopes are opposing meaning one (rule 1&2) positive and one (rule 1&2) negative then you must add.
    ((( negative and positive always have same meaning,, clearly defined in rule 1&2)))

    There’s 3 simple rules, only 3 and each based on the one prior.
    Don’t play with anything like an unspoken 4th rule and you’ll be fine. Don’t switch meanings or exclude anything from the term “everything” and you’ll be fine. Don’t deviate from rule 1 in any way.
    Perfect every single time, pretty simple and easy.

    Especially don’t add a fourth rule that violates any parameter set forth in rule 1, 2, 3.

    Spotting the 4th rule out in the wild.

    That sabotaging imposter 4th rule would include a violation of rule 1 and thus changing directions. The imposter sabotaging 4th rule would require that you violate rule 2 and call that negative slope on the pinion as up. The imposter sabotaging 4th rule would require you to violate rule 3 exactly correctly (((( can one violate any rule exactly correctly))) or fuck everything up, get confused, seek help and run into nothing but confusion with other confused people explaining why or which parts of sabotaging imposter rule 4 is more important.

    Stay away from rule 4, ignore the many pictures you’ll undoubtedly find of rule 4, you’ll be fine if you know rule 4 when you see it. Rule 4 is not rule #1, but sometimes you’ll see folks using rule 4 as their own guide.

    That’s as simple and to the point as I can get it. Go ahead and play with rule 4 if you must, if you learned rule 4 before learning 1,2,3 then you’ll most likely have to explain why rule 4 is relevant and how to navigate rule 4 to achieve a correct outcome.
    Last edited: Sep 20, 2023
  2. BJR
    Joined: Mar 11, 2005
    Posts: 9,384


    This is the Hamb, a bunch of hoodlums don't obey rules. Geometry yes, rules no. :p
    Pist-n-Broke and dana barlow like this.
  3. 1971BB427
    Joined: Mar 6, 2010
    Posts: 8,549

    from Oregon

    Just one thing to add that makes guys go crazy, and that's offset pinions. Guys get all wound up wondering how to compensate for the pinion not being centered! The real answer is it doesn't matter, so quit thinking about side offset when setting up your driveline angles.
  4. Happydaze
    Joined: Aug 21, 2009
    Posts: 1,747


    The first rule of pinion angle club is that we don't talk about......

    Ned Ludd, clem and Just Gary like this.

  5. Easy. Just NEVER cross swords. A good edict for life actually ;)
  6. Johnny Gee
    Joined: Dec 3, 2009
    Posts: 12,223

    Johnny Gee
    from Downey, Ca

    How many shot’s of caffeine did Starbuck’s put in your coffee?
    Joined: Jun 3, 2005
    Posts: 10,038


    Bruh, you forgot something.
    The 5th Dimention told us of "1 less..." so even they knew there was no 4th.
    See? We all got 1 less egg to fry. Works for me...;)
    31Vicky with a hemi likes this.
  8. belair
    Joined: Jul 10, 2006
    Posts: 9,006


    Just because you don't know the rules, it doesn't mean they don't apply to you.
  9. There’s really no debating it. It’s cut dry and simple.
    What you find is people trying to discuss the 4th rule.
    427 sleeper and Pist-n-Broke like this.
  10. Nice and quiet here.
    maybe this should be a sticky :)
    427 sleeper likes this.
  11. bchctybob
    Joined: Sep 18, 2011
    Posts: 5,006


    Well stated but remember, you have to consider the 5th Dimension when you let the sunshine in during the age of Aquarius also.
  12. Corn Fed
    Joined: May 16, 2002
    Posts: 3,243

    Corn Fed

    And the Lord spake, saying, ''First shalt thou take out thy Holy Angle Finder. Then shalt thou count to three, no more, no less. Three shall be the number thou shalt count, and the number of the counting shall be three. Four shalt thou not count, neither count thou two, excepting that thou then proceed to three. Five is right out. Once the number three, being the third number, be reached, then settest thy Pinion Angle towards thy transmission, who, being in My sight, shall match it.'
    Last edited: Sep 21, 2023
    Anderson likes this.
  13. He set it up that way
    427 sleeper likes this.
  14. Seems you know how to successfully navigate rule #4 and get the correct outcome.

    Equal but opposite means - opposing angles that intersect - Equal but opposite literally means not parallel everywhere and any place except in rule #4 when it precisely violates both rule 1 & 2 just right.

    Parallel meaning both negative or both positive . Not trans down pinion up. Rule 4 violates rule 2 but if violated correctly you can still get the math right using the correct flip backwards on when to add or subtract.
    427 sleeper likes this.
  15. Who's on first?
    jimmy six, Ned Ludd and CSPIDY like this.
  16. CSPIDY
    Joined: Nov 15, 2020
    Posts: 389


    Is there a tangent angle somewhere in the 4th rule?
  17. It's amazing how 3 simple rules can totally confuse the majority of builders and have so many asking for information about it over and over and over even here on the H.A.M.B. We now should do a big sticky about how to use the Search menu on the Top of this page and every page here.
    427 sleeper likes this.
  18. jimmy six
    Joined: Mar 21, 2006
    Posts: 14,221

    jimmy six

    It’s invenerial as far as I’m circumcised.
    427 sleeper likes this.
  19. Ned Ludd
    Joined: May 15, 2009
    Posts: 4,940

    Ned Ludd

    I believe I know what you mean by "Rule 4" — though it's more an alternative set of rules than a fourth rule. There is one situation in which it'll work, i.e. when there is no vertical movement of the rearend in relation to the chassis, as with an IRS or a DeDion setup. If there is vertical movement, the rule would be satisfied only at ride height, and would go wrong as soon as there is any suspension movement.

    I suspect that it is also easier to get wrong, as we'd be dealing strictly with transmission-to-driveshaft and driveshaft-to-pinion angles, and wouldn't have the option of relating everything back to a common datum like the floor.
    Budget36 likes this.
  20. goldmountain
    Joined: Jun 12, 2016
    Posts: 4,301


    My rule for pinion angle is simply tack weld it together the first time since it will be easier to take it apart to do it right the second time.
  21. Well just about anything that violates rules #1 #2 & #3 is rule #4. 1,2,3 always work every time and always, that’s why they are rules.

    An alternative set of rules that only works out OK sometimes is exactly what rule #4 is. Rule 4 is confusing and requires vast amounts, volumes upon volumes of text to explain how to use it. Even though if it where completely explained with every flip of function exactly perfectly, there’s no reason to believe it would be read in its entirety, or followed by someone performing the exercise and they not miss the precision application of flip and the corresponding re-flip.
    Oh it can be done., I’m not saying anything like that at all. I take alternate paths too, most people call it a wrong turn and usually happens when I really needed to go the right way because I don’t know where I am.
    ( guy’s asking about pinion angles don’t know where they are going either)

    Very simply- following those rules 1,2,3 in their entirety is 100% guaranteed path to success every single time without exception or further explanation
    427 sleeper likes this.
  22. hemihotrod66
    Joined: May 5, 2019
    Posts: 968


    I run 3 degrees nosed down for my hotrod that has trailing arms and coilovers....Chrysler use to recommend 7 degrees nose down on there superstock cars and the pinion snubber set one inch from the floor....
  23. Chavezk21
    Joined: Jan 3, 2013
    Posts: 759


    Pictures would help. All those written rules confuse me. o_O
    clem likes this.

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