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Technical pinion angle ?

Discussion in 'Traditional Hot Rods' started by johnrfray, Aug 10, 2019.

  1. Blues4U
    Joined: Oct 1, 2015
    Posts: 5,686

    Blues4U
    Member
    from So Cal

    I think he was talking about those who are posting advice, who can't formulate a reasonable sentence and just add confusion with their poor writing and mathematical skills. And I agree with him, take a look at some of the posts in this thread, up/down, symmetrical/asymmetrical, they just add confusion instead of clarity.
     
  2. rooman
    Joined: Sep 20, 2006
    Posts: 4,052

    rooman
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    I was talking about something that is at least close to being properly engineered. ;)

    Roo
     
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  3. gimpyshotrods
    Joined: May 20, 2009
    Posts: 18,330

    gimpyshotrods
    ALLIANCE MEMBER

    Working angles need to be equal, and minimal. One single sentence. Done.

    Crankshaft and pinion center lines need to be parallel with each other, and the chassis center line, when viewed from the top.

    Crankshaft and pinion center lines need to be parallel with each other, when viewed from the side.

    The angle between the crankshaft and pinion center lines, and the driveshaft should be as shallow as is practical, to maximize u-joint life, and to minimize vibration. The most commonly quoted number is 3º.
     
  4. OLDSMAN
    Joined: Jul 20, 2006
    Posts: 2,422

    OLDSMAN
    BANNED

    The clarity and advice isn’t the best sometimes, but you still have to try to help. 2OLD2FAST had to learn someplace. He wasn’t born with the knowledge in his head
     
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  5. jaw22w
    Joined: Mar 2, 2013
    Posts: 1,245

    jaw22w
    Member
    from Indiana

    The problem does become a little more complex with a leaf spring suspension. I agree with everything you said except the above part of the quote. The math used in figuring your u-joint working angle will tell you this is wrong.
     
  6. Andy
    Joined: Nov 17, 2002
    Posts: 4,765

    Andy
    Member

    A lot of very confident statements about the trans and rear angles having to be parallel. That is a valid design but not the only one. Go look at the angles and shaft designs used in the 58-64 Chevys. They made a few of them and nothing is parallel. I can post from the shop manual.
    Having the working angles the same is the real goal. Often due to the rotation of the rear end about a point beween the u-joints, having the rear end point down is better. It reduces the angle change between the joints with rear end movement. Most production vehicles use this design.
     
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  7. rooman
    Joined: Sep 20, 2006
    Posts: 4,052

    rooman
    Member

    If the engine/transmission package is set very low in the frame and the vehicle has large diameter rear tires (and does not have a rear end with a pinion that is low relative to the ring gear) it is not impossible for the driveshaft to run uphill from the transmission. The rules regarding U joint angles still apply but the schematic will not look like the ones shown above.

    Roo
     
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  8. jaw22w
    Joined: Mar 2, 2013
    Posts: 1,245

    jaw22w
    Member
    from Indiana

    Yep. It is possible to have an uphill driveshaft. The engine in my 27 roadster has only 4" ground clearance. The Frankland QC mounts 30" MT tires. The driveshaft is uphill 1.1*. The trans is 2* downhill for a 3.1* u-joint working angle. On the high side but acceptable. If the DS had run down hill 1.1*, the WA would be .9*
     
  9. I know that, however remember where you are.
    Spring rate be damned- discard that spring material and the car rides lower.

    I’m a bit cautious on offering up a guess to the percentage of cars on this website the have a driveshaft running up hill to the rear- a natural consequence of lowering a vehicle. Another good number of vehicles have a substantial rubber rake. Both of these situations have specific and unique details to get them right.
     
  10. impala4speed
    Joined: Jan 31, 2010
    Posts: 260

    impala4speed
    Member

    This is a very interesting and timely subject for me as I'm about to do this as well. I have enjoyed many of the comments and have learned something from them. The above quote however, even if true, was not helpful.
     
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  11. This is the ideal and somehow has become the Holy Grail, with guys obsessing over it. Don't get me wrong, following this should result in geometry good enough for nearly all purposes. But achieving this as a practical matter is another kettle of fish entirely. As the video above illustrates, those angles don't stay static but move constantly in most cases. And as has been pointed out, there's plenty of OEM examples that miss the mark with no apparent detrimental effects in normal use.

    If using a ladder bar/wishbone style rear suspension, I'd be tempted to increase the pinion angle slightly as it will decrease as the suspension compresses.

    Any other type of suspension, I'd decrease the pinion angle slightly to allow for deflection under load. How much is an open question, as every suspension will be different. Suspension geometry will play a big part in any decision.

    And the question of up or down angle of the driveshaft is vastly overrated IMO. Sure, it the angle gets too big you'll have issues (think lifted off-roaders or street freaks) but there's also plenty of examples with very small or no angle. Look under vehicles with IRS, I'm not aware that their u-joint life is compromised enough to worry about.
     
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  12. rooman
    Joined: Sep 20, 2006
    Posts: 4,052

    rooman
    Member

    My OT daily driver ( a 96 Silverado stepside) is lowered 3 (tubular arms) and 6 (flip kit) and I just went out and put the digital protractor on it. Actually it is surprisingly good as it sits with the engine and pinion angles within half a degree of each other and about 1.5 degrees of driveshaft angle. This one has over a quarter of a million miles on it but probably only about 25K since it was dropped. My previous truck had the same package and I put about 140K on it after I lowered it.
    On the subject of factory installations a C3 Corvette has the engine significantly off center to the right as do most Mopars. Not sure about the C body Mopars but the A and B series cars have it moved over to make room for the steering box.

    Roo
     
  13. gimpyshotrods
    Joined: May 20, 2009
    Posts: 18,330

    gimpyshotrods
    ALLIANCE MEMBER

    How many shaft sections are in that driveshaft?
     
  14. s55mercury66
    Joined: Jul 6, 2009
    Posts: 3,980

    s55mercury66
    Member
    from SW Wyoming

    Likewise V8 powered first gen Firebirds and big block Camaros.
     
  15. Andy
    Joined: Nov 17, 2002
    Posts: 4,765

    Andy
    Member

    driveshaft4.JPG
    Two with a center support bearing. No constant velocity joints.
     
  16. You guys are right. Also Chevy II's are offset. But the pinion is also offset 1" , so basically not an issue.
     
  17. s55mercury66
    Joined: Jul 6, 2009
    Posts: 3,980

    s55mercury66
    Member
    from SW Wyoming

    That I did not know, but basically, as long as the transmission and pinion centerlines are parallel when viewed from above, and the driveshaft angle is within reason, all will be good, yes?
    PS, these pinion angle threads always turn out to be as good as the "my motor has a miss" threads.
     
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  18. I have an OT C-60 bus with 4 shafts. Years ago I changed the pig to a 2- speed and the pinion was to the right and down from the original location about 4".
    I had all the angles right and it rumbled really bad at hi-way speeds.

    I didn't know what to do, so I drove it that way for a long time. Finally I moved the last mid-ship bearing to the right about 2" and it quieted right down.
    Looking at the shaft from underneath, it looks like a swimming pool noodle.
    It has about 450,000 miles on it now and only changed the u-joint once since.

    I think we call that "Yankee Enginuity". :D
     
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  19. Dick Stevens
    Joined: Aug 7, 2012
    Posts: 3,156

    Dick Stevens
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    That would be "ingenuity" :rolleyes::D
     
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  20. Not at my house... :D
     
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  21. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 3,382

    2OLD2FAST
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    from illinois

    I wasn't talking about possessing the knowledge , I was mainly talking about the ability to read and write , basic uncomplicated communication, Get it ?
     
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  22. OLDSMAN
    Joined: Jul 20, 2006
    Posts: 2,422

    OLDSMAN
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  23. OLDSMAN
    Joined: Jul 20, 2006
    Posts: 2,422

    OLDSMAN
    BANNED

    no response needed
     
  24. eicke
    Joined: Jul 30, 2012
    Posts: 63

    eicke
    Member

    The reason the diff should be dropped 2.5 to 3 degrees,
     
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  25. X-cpe
    Joined: Mar 9, 2018
    Posts: 1,189

    X-cpe

    Will Rogers said,"Everyone is ignorant, only on different subjects." Fortunately those skills are not a requirement to join or use this forum. Would it be nice if everyone had those skills? HELL YES! Why don't they have these skills? Lack of ability, lack of desire, lack of opportunity, learning disabilities, laziness? Doesn't matter, we have to deal with what is, not what we wish was. If it is too bothersome just skip on by. If on the other hand it interests you, or you think you can help, use your superior skills to try and discipher what is there and ask simple questions to clarify things. Don't ask them to count to 21 with their fly closed. It's surprising how much it helps your understanding of things when you have to break them down to their simplest components to help someone else understand them. Some of them have skills and knowledge that you and I will never attain in our fondest dreams.
    When my buddy and I went racing 20 years ago we went on forums to figure things out. (I still have a stack of threads and posts that we printed out that is over a foot high.) Some of those old boys had no acquaintance with spelling, punctuation, capitalization or syntax. It might take 15 minutes to discipher a ten line paragraph, but they could damn sure make them turn left and fly. My buddy's saying was "We might be smarter than they are but they know more than we do."
     
    Last edited: Aug 12, 2019
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  26. gimpyshotrods
    Joined: May 20, 2009
    Posts: 18,330

    gimpyshotrods
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    Exactly my point. This thread is about a one piece driveshaft.

    You have brought in an example that does not apply here.
     
  27. OLDSMAN
    Joined: Jul 20, 2006
    Posts: 2,422

    OLDSMAN
    BANNED

    Very well said. This is my thoughts totally!
     
  28. Pinion angle set up rules should be segregated into groups.
    First Drive shaft slope : up to the rear and drive shaft slope down to the rear.
    Then rear suspension: Leaf springs and everything else.
    Then main usage of vehicle.

    The principals remain the same but the details change some. For instance- if the drive shaft slopes up to the rear (any lowered car) then beginning with the trans down to the rear is going to make your drive line set up more difficult.
     
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  29. prpmmp
    Joined: Dec 12, 2011
    Posts: 1,078

    prpmmp
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    I believe Will Rodgers also coin the phrase, The more people I meet the more I like my dog! ( Probably not the exact way He said it because I right and reed like a 2nd grader!) Pete
     
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  30. Sporty45
    Joined: Jun 1, 2015
    Posts: 989

    Sporty45
    Member
    from NH Boonies

    I always liked this vid for helping to understand the affect of pinion angle changes.


     

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