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Technical Another Pinion Angle question.....

Discussion in 'The Hokey Ass Message Board' started by tlmartin84, Jan 31, 2022.

  1. tlmartin84
    Joined: Jul 28, 2011
    Posts: 1,030

    tlmartin84
    Member
    from WV

    So I set all of this up so that everything is basically in a straight line.

    Engine is 2.3 degrees down, pumkin is 2.3 degrees up, and the driveshaft is perfectly in line.

    Do you think I should rotate the pumkin down a degree or so? Or leave it?

    20220131_133616_HDR.jpg 20220131_133622_HDR.jpg 20220131_133743_HDR.jpg 20220131_133859_HDR.jpg
     
  2. hemihotrod66
    Joined: May 5, 2019
    Posts: 968

    hemihotrod66
    Member

    Pinion should be at least 3 degrees nose down... This makes the needle bearings in the U-joint rotate....
     
  3. hepme
    Joined: Feb 1, 2021
    Posts: 519

    hepme
    Member

    "equal and opposite" was always the rule i read. You got that, should be o.k. 2-3 degrees seem standard.
     
    Tman likes this.
  4. FrozenMerc
    Joined: Sep 4, 2009
    Posts: 3,093

    FrozenMerc
    Member

    2 things to consider.

    1. Pinion and Transmission output shaft should be PARALLEL. It looks like you are there.

    [​IMG]

    2. The driveshaft should be have at least 1 deg of angle between it and the pinion / transmission. This allows the U-Joint bearings to move as Hemihotrod66 alluded to. However, the rear suspension is always moving when you are driving, unless you only drive on glass smooth roads, so the conventional thinking about needing an included angle is a bit overdone.

    [​IMG]
     
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  5. A 2 B
    Joined: Dec 2, 2015
    Posts: 491

    A 2 B
    Member
    from SW Ontario

    After the chassis is loaded with the full assembled weight it will be time to revisit pinion angles. Any needed adjustments can be made then but without assembly you could set an estimated amount of weight distributed on the chassis now to simulate final ride pinion angles. Beautiful chassis construction!
     
    Almostdone likes this.
  6. alchemy
    Joined: Sep 27, 2002
    Posts: 20,406

    alchemy
    Member

    I’m no engineer, but I’d shoot for the trans and rear having equal but opposite angles like you have before messing the alignment trying to make the joints “work the grease”.
     
    2OLD2FAST likes this.
  7. gnichols
    Joined: Mar 6, 2008
    Posts: 11,345

    gnichols
    Member
    from Tampa, FL

    Sounds good to me but I think it's best to know where the diff is at ride height, fully loaded. But I just don't know how you do that during construction. Maybe it doesn't matter that much as long as you start out ok?
     
  8. squirrel
    Joined: Sep 23, 2004
    Posts: 55,939

    squirrel
    Member

    I'd either leave it as you have it, assuming you can make minor adjustments later to the length of the lower bars.
     
    Mark Yac and joel like this.
  9. It appears to me that your trans, driveshaft and pinion form a straight line. The image/chart above describes that as being "OK". As mentioned though, some difference between the driveshaft and the trans/pinion is 'better' in order to get the U-joints working/moving. That being said, the difference can be found if the pinion is offset in the chassis.

    When viewed from above, is your trans perfectly in line with your pinion (centered engine/centered pinion) or is there some offset there?
     
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  10. tiredford
    Joined: Apr 6, 2009
    Posts: 560

    tiredford
    Member
    from Mo.

    I spent some time in a pit with new Ford trucks rolling over me at one every minute. I saw a shit ton of trucks that the shaft was dead level, straight out of the trans into the rear end. I think the roller bearings must rotate when the suspension goes up and down. Just a guess.
     
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  11. tlmartin84
    Joined: Jul 28, 2011
    Posts: 1,030

    tlmartin84
    Member
    from WV

    It is slightly offset so it should take care of the bearings.
     
  12. Almostdone
    Joined: Dec 19, 2019
    Posts: 892

    Almostdone
    ALLIANCE MEMBER

    The general rule of ‘3 degrees’ and parallel for trans and pinion assumes a driveshaft angle of zero degrees. Driveshaft angle is taken into account along with the trans and pinion angles to arrive at the angle at each u-joint, which is what the ‘3 degrees’ generalization refers to (it IS a generalization).

    Spicer has a nice tool to calculate such things:

    https://spicerparts.com/calculators/driveline-operating-angle-calculator

    Your current angles are fine, but need to be finalized with the car at ride height.

    John
     
  13. tlmartin84
    Joined: Jul 28, 2011
    Posts: 1,030

    tlmartin84
    Member
    from WV

    It is at ride height now. Any weight from the body will be compensated for when I tighten up the springs.

    20220131_160003.jpg
     
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  14. Almostdone
    Joined: Dec 19, 2019
    Posts: 892

    Almostdone
    ALLIANCE MEMBER


    That’s some beautiful work there, sir.

    I can’t tell from the picture if there is a slight side-to-side angle in the driveline - if so, that counts too.

    John
     
  15. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 5,216

    2OLD2FAST
    Member
    from illinois

    Is the trans not centered in the frame ?
     
  16. trans looks offset to the passenger side.
     
  17. A 2 B
    Joined: Dec 2, 2015
    Posts: 491

    A 2 B
    Member
    from SW Ontario

    Now would be a good time to shoot some laser lines.
     
  18. jimmy six
    Joined: Mar 21, 2006
    Posts: 14,799

    jimmy six
    ALLIANCE MEMBER

    Watch a YouTube of a dirt track modified rear end movement camera and you will never worry or think of a U-Joint again..
     
    Tman likes this.
  19. tlmartin84
    Joined: Jul 28, 2011
    Posts: 1,030

    tlmartin84
    Member
    from WV

    Haha, more worried about vibrations!
     
  20. tlmartin84
    Joined: Jul 28, 2011
    Posts: 1,030

    tlmartin84
    Member
    from WV

    Everything is offset about 1.5 inches to the passenger side with the rear diff a bit more.

    Beauty of a straight 6.

    20220117_170036_HDR.jpg 20211231_163107_HDR.jpg
     
    Last edited: Jan 31, 2022
  21. tlmartin84
    Joined: Jul 28, 2011
    Posts: 1,030

    tlmartin84
    Member
    from WV

    Ha what for?
     
  22. A 2 B
    Joined: Dec 2, 2015
    Posts: 491

    A 2 B
    Member
    from SW Ontario

    Just another tool I find very helpful.
    Before the body is lowered on to the chassis it is easy to position a line laser from a suitable height mounted on a tripod. This allows you to very accurately pinpoint center of or offset of each component. The front cross member, engine damper/ centerline, transmission output shaft, driveshaft yoke, rear axle position/ squareness will all be visible at the same time in relation to where everything should be.
    It is just an easy way to fine tune the driveline alignment. There is nothing wrong with having offsets but they need to be consistant from one end of the drive train to the other, to minimize possible unwanted vibration. The same + or - pinion angles apply when viewing from a side view perspective or from above. I don't know of a better way to do this without some very sophisticated equipment.
    Once the body is mounted, it will be much more difficult.
     
    Last edited: Jan 31, 2022
  23. gimpyshotrods
    Joined: May 20, 2009
    Posts: 23,264

    gimpyshotrods
    ALLIANCE MEMBER

    This is a commonly held misconception.

    No offset is required in a driveshaft that is attached to a moving suspension element.

    If the differential center section were fixed-mount like a Jag or a Corvette, then no angle would decrease u-joint life.

    The normal function of suspension articulation is more than enough to distribute lubrication.
     
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  24. tlmartin84
    Joined: Jul 28, 2011
    Posts: 1,030

    tlmartin84
    Member
    from WV

    I actually used a string line to set everything off of. However mixing and matching axles, engine mounts/crossmembers the drive line sort of "is what it is".

    The 8.8 is out of a 94 crown vic, with an offset diff. The front cross member is a 2004 crown vic (which has offset motor mounts) and lastly the inline six crank is offset to one side compared to it's mounts.
     
  25. hepme
    Joined: Feb 1, 2021
    Posts: 519

    hepme
    Member

    I'm sure you are aware that the offset in the rear can be solved by using another short axle (pass. side i think) in place of the long one. Have to cut/weld the housing but no big deal and it centers the pinion perfectly. I did this to an 8.8 in a coupe, works great.
     
    Almostdone likes this.
  26. Budget36
    Joined: Nov 29, 2014
    Posts: 13,174

    Budget36
    Member

    But then his rearend would be to narrow for his plans as built.
     
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  27. tlmartin84
    Joined: Jul 28, 2011
    Posts: 1,030

    tlmartin84
    Member
    from WV

    Correct, and it would throw out the angle even worse with the offset engine.
     
  28. lippy
    Joined: Sep 27, 2006
    Posts: 6,825

    lippy
    Member
    from Ks

    Ma mopar offset all her engines a couple inches or so. No problems.
     

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