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Technical Looking for tips

Discussion in 'Traditional Hot Rods' started by chris101_ny, Apr 20, 2021.

  1. chris101_ny
    Joined: Aug 3, 2011
    Posts: 92


    I have a 31 sedan I’m am building. I currently have the wheels on the axles and frame resting on the both sets of leaf springs. I am ready to shackle the leaf springs to the cross members, weld the brackets to the frame for the front radius rods, and weld brackets to the frame and rear axle for the rear radius rods. I am using the stock frame I have boxed and added a k member to, have a 4” dropped axle for the front, and a Chrysler 8.8 for the rear. I know I should have 5* to 7* caster for the front. Should the rear axle be perpendicular to the ground? I would appreciate any other wisdom anyone can offer before it becomes permanent too.
    Thanks in advance
    IMG_1436.JPG IMG_1437.JPG

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    dana barlow likes this.
  2. You need a Model A type spring for that rear cross member. The shape needs to follow the shape of the crossmember and have the centre bolt poke through the hole at the top.

    Unless you've done something to the cross member that I can't see.

    Also, nothing should be finish welded to the diff until your pinion angle is set.
    Likewise front hairpin brackets (allowing for caster) until the chassis is at loaded ride height.
    dana barlow and pprather like this.
  3. evintho
    Joined: May 28, 2007
    Posts: 2,056


    What he said^^^!
    I'm sure you're anxious to get it up on 4 wheels to see the semi-finished product but, fight that urge! Put an angle gauge on top of the kingpin boss to get your 7* of caster then tack your radius rod brackets to the frame. Do the same with an angle gauge on the rearend, making it 3* up, then tack the R/R brackets in place. You'll need to fab up your motor mounts and trans mount too. Then, set your engine/trans in place and make sure the tailshaft is 3* down. Don't forget your shock mounts. When everything is where it should be......then finish weld.
  4. chris101_ny
    Joined: Aug 3, 2011
    Posts: 92


    That is all great advice, thanks! I am getting excited, especially bc this is my first build, but I’ll keep it in check! The rear leaf spring doesn’t drop into the rear cross member bc there a couple of shackles in the way. I was thinking I could just take them off bc the pin in the center holds all the leaves together and I figure the cradle for the spring would keep the leaves together and where they should be. The frame it came off of just had it shackled to a homemade frame. There are brackets attached to the axle in the pics but I already cut them off bc they were in the wrong location for a stock frame.
    IMG_1419.JPG IMG_1421.JPG

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  5. HotRodWorks
    Joined: Dec 6, 2005
    Posts: 358

    Alliance Vendor

    No. As mentioned above, the spring doesn’t fit because it’s the wrong spring. You need a Model A spring for the rear. Do that before you do any thing else.

    Look at some pictures of a model A spring and compare to yours.

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  6. 31Apickup
    Joined: Nov 8, 2005
    Posts: 2,956


    The model A spring mounts above the axle, unless the frame was stretched, your wheelbase will be way off with a spring behind.

    Sent from my iPhone using The H.A.M.B. mobile app
  7. The way things are now, when you sit the Body in correct place on the Frame your rear Tires are going to be 6" forward of where they belong in the rear wheelhouse on the Body.
  8. Excellent point...I can't believe I missed that.:eek:
  9. Fortunateson
    Joined: Apr 30, 2012
    Posts: 4,657


    The rear shock neglect looks too severe to me but I may be wrong.
  10. An easy solution to the rear wheelbase would be to build a spring perch on the back much like you see on the Front of most T Bucket's you see. There's plenty off floor pan to keep things under the Body. I'd still change to a Model A spring just because it looks correct.
  11. Cleat
    Joined: Jul 10, 2018
    Posts: 29

    from Gifford WA

    Additional with the spring behind and no step in the frame. There's a risk of the frame hitting the axle over large bumps.... Ask me how I know. With a your setup I suggest spring over axle as well. If you want it really low find a Model T rear spring. But what you have there is a great start!

    Sent from my SM-G960U using The H.A.M.B. mobile app
  12. Rynothealbino
    Joined: Mar 23, 2009
    Posts: 261


    What is your wheelbase set at? As others have said, you need a model A or T style spring to use with that crossmember. These traditionally mount above the axle, so I suspect your wheelbase is shorter than you want right now. To use the spring you have you would need to replace the crossmember entirely, which you can do while you Z and extend the frame. Lots of different ways to go about this.
  13. dana barlow
    Joined: May 30, 2006
    Posts: 4,777

    dana barlow
    from Miami Fla.
    1. Y-blocks

    It's OK to have spring behind rear axle,it just makes WB shorter and lowers the frame in rear. This in turn make mounting the body odd,yet in some cases, it means you make things fit as needed. I had too build my own front cross to hold front spring more forward. So body shifted forword on frame as well. If your going to run fenders? Moving body forward my not be EZer then shifting axles each forward or to stock local.
    Rear spring is the wrong one that you have, get a "A" spring or even a "T" will work,or make a custom rear cross. The rear shock mounts on rear are wrong placement, much too far too center of rear=shocks don't work in the center of rear axle well.. My own Bobtail roadster 28A has spring behind rear,but it is a 1928 Model A spring and rear shocks are much closer out to tires.
    As for rear end pionangle,; if engine an tranny will be level with the ground,so should the rear be.

    015.JPG A nother show.jpg
    Last edited: Apr 21, 2021
    ekimneirbo likes this.
  14. 1971BB427
    Joined: Mar 6, 2010
    Posts: 7,474

    from Oregon

    Rear pinion angle should really wait to be set after engine/trans is in so it can be correctly done.
    X38 and ekimneirbo like this.
  15. ekimneirbo
    Joined: Apr 29, 2017
    Posts: 2,793

    from Brooks Ky

    You need to get a copy of a Pete and Jakes Catalog or one of the various chassis books on Amazon that explains the relationships between your steering components...........before you buy anything or weld anything. It all just doesn't bolt in place and necessarily work correctly if you don't do it the right way. You need to get all the info to make the right decisions.
    Bump Steer 1 001.jpg
    Bump Steer 2 001.jpg
    Bump Steer 3 001.jpg
  16. chris101_ny
    Joined: Aug 3, 2011
    Posts: 92


    This is exactly what I needed, thank you! The current spring is 43 3/4" eye to eye. I found a thread on the hamb about this very topic. I will definitely get the new spring, tack where brackets should go, add the weight of the engine/trans, and remeasure everything before the final weld. I do want the car as low as it can go with the frame I have so it seems like it'll be a T spring with a couple of leaves taken out. I will get Pete and Jake's catalog too. thanks again!
  17. P&J information is also available on line via their website.

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