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Technical AV8 pinion angle issue

Discussion in 'Traditional Hot Rods' started by fiftiescat, Aug 9, 2022.

  1. fiftiescat
    Joined: Jan 22, 2013
    Posts: 200

    fiftiescat
    Member
    from NY

    I’m at the point in the build where I’m getting ready to lock the engine/transmission down and shorten the torque tube & driveshaft.

    ‘31 body & chassis, ‘39 trans & ‘39 banjo. Millworks AV8 rear spring and bolt on spring mounts. With the spring installed and u-bolts tight, the pinion angle is down like 7 degrees… I loosened the u bolts and jacked the pinion up and re tightened the u bolts and now it’s still down about 1 degree, but I didn’t want to keep jacking up the pinion… this is one of those things where I don’t know if I’m over thinking & analyzing, or if I’m missing the boat completely. The spring hangers are labeled left and right and on correctly….

    Usually the tube is on the rear and I connect it to the trans first and then raise the rear into the crossmember so I’ve never had to address this issue. Thanks!
     

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  2. adam401
    Joined: Dec 27, 2007
    Posts: 2,856

    adam401
    Member

    Put a bar in the coupler and jack the shit out of it. I do it for every torque tube I measure to shorten
     
    fiftiescat likes this.
  3. fiftiescat
    Joined: Jan 22, 2013
    Posts: 200

    fiftiescat
    Member
    from NY

    That’s what I was thinking! I was just concerned about the stress on the shackles/bushings etc
     
  4. You are working against the spring, twisting it. You can either bolt the torque tube on and bolt it all up or A- modify to shackle brackets on the rear to angle the housing up or B- cut and weld the rear spring crossmember parallel to the angle of the rear when at ride height so that the spring will not be I. A bind (twist) when compressing in the arc of travel dictated by the angle the spring shackle brackets. If you match the angles up at ride height so there is no twist on the spring it will ride much smoother. The chive is yours. But if you just jam the spring in the crossmember twisted, and you are using shackle bushing that are plastic like from speed way or Pete and Jake’s, the won’t last long. Stock type with the link and bolt will work fine.
     
    Kiwi 4d likes this.

  5. fiftiescat
    Joined: Jan 22, 2013
    Posts: 200

    fiftiescat
    Member
    from NY

    I was thinking of messing with the spring mounts…. I think they sell degreed ones for quick change applications that point the rear up towards the transmission. I am using stock style bushings in the rear, by the way. Those plastic ones are junk.
     
  6. Marty Strode
    Joined: Apr 28, 2011
    Posts: 8,796

    Marty Strode
    Member

    You need to cut and install the torque tube, and deal with the spring/hangers later, that dictates the pinion angle.
     
  7. Pete Eastwood
    Joined: Jul 27, 2011
    Posts: 1,324

    Pete Eastwood
    Member
    from california

    For mock up, just use only the main leaf !
     
    Pist-n-Broke likes this.
  8. brokenspoke
    Joined: Jul 26, 2005
    Posts: 2,968

    brokenspoke
    Member

    On my RPU with a quick change I had to swap the arms to left to right/right to left to raise the pinion angle
     
  9. 100% Matt
    Joined: Aug 7, 2006
    Posts: 2,747

    100% Matt
    Member

    Get your torque tube bolted up. The TT controls the position of the pinion. Additionally you want the weight on the spring. So ditch those jack stands and get all four wheels on the ground. The lower and deeper the rear goes into the body also effects your pinion angle. Thankfully closed drive set ups are not very pinion angle dependent. An open drive conversion is a whole other can of worms.
     
    fiftiescat and Nailhead Jason like this.

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