Announcement

Collapse
No announcement yet.

Front leaf springs- shackle placement

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Front leaf springs- shackle placement

    My '30 Chevy truck originally came with the shackles mounted on the back side of the front axle. To my knowledge, '37-'46 they changed the design and started putting the shackle in front of the axle .

    Why?

    Is there any nuance affect in steering or drive-ability? Was this change done to correct something or one of those "it ain't broke so let's fix it" scenarios? Inquiring minds want to know...

    The reason for asking is that original spring eye to center is 17" in front (pivot point) and 19" in the back (shackle location). 39-46 has the exact same 17/19 dimensions. Great upgrade! BUT- they flipped the mounting and have shackles in front, pivot point in back. The bushing O.D. is the same dimension on front and back so I can swap those out and keep things simple.

    Again, that just makes me curious if there is a benefit with the shackle in front.
    https://www.killbillet.com/forum/30s...the-30-chevyMy 1930 Chevy truck build link:

  • #2
    My wild and crazy guess would probably be to maintain the wheel base length as the load changed, probably something related to the invention of 4 wheel drive.
    When the front spring is mounted with a fixed front location, when the weight load increased on the spring, it would flatten out, and would move the center bolt on the axle towards the rear. Depending on how much arch the spring had, and how much it would deflect under weight probably wouldn't amount to a lot of movement, but under some conditions, I suppose a 1/4" may be possible. The early 4x4 front ends were pretty limited on how much movement they could tolerate in a compression side of things, and its possible the movement could have put too much stress on the front drive axle. By mounting the rear of the spring solid and having the shackles at the front, any axle movement would be forward, one would think any forward movement would be pretty tough to get, but forward axle movement would not cause compression on the front drive axle.

    Or it could have just been easier to assemble at the truck factory with the stationary rear spring mount rather then a stationary front spring mount.

    Or it could have been some engineer saying "Look, lets move this from here to here."

    In defense of the 4x4 deal, you still see a lot of modern 4x4 trucks that have front leaf spring with the stationary rear spring mounting locations. That's my story, and I'm sticking to it until someone comes up with a better idea.... LOL! Gene

    Comment


    • #3
      Originally posted by Gene View Post
      .....That's my story, and I'm sticking to it until someone comes up with a better idea.... LOL! Gene
      LMAO! My lifelong hot rod buddy mentioned the 4x4 thing also. Lots of little nuances there.

      Someone on the Stovebolt forum took some pics from a book they had showing the progression changes of Chevy vehicles year to year, giving reasons why they changed what they did. It was amazing and I want one now.

      In '37 they switched to shackle in front saying there was an ever so slightly less deflection in the steering arm connection- but I noticed they had also moved the steering gear box closer to the axle. I've got to fab some hangers anyway so I do believe I'll just roll with the '37 design and put the shackle in front. We'll see. Worse thing that can happen is to change something latter- nothing that will keep the sun from rising.





      https://www.killbillet.com/forum/30s...the-30-chevyMy 1930 Chevy truck build link:

      Comment


      • #4
        So, you have a hot rod buddy that had the same thoughts as I did? WOW! That is pretty darned scary! Are you trying to telling me there are two, and maybe more, of us crazy old hot rodders? LOL!

        You will be fine using the 37 design. Dodge 4x4 trucks used the front shackle on the front leaf springs up through the 93 model year. In the all new 94 Dodge trucks, they used coil springs instead of leafs in the front.

        That book on changes for the Chevy vehicles over the years would probably be a good read, and I'm not even a Chevy guy. I'd have to wonder how much was actual fact and not BS though (not like the "facts" I stated earlier. I can't believe your going to take the words out of an official book from GM over the collective guessing from 2 of your hot rod buddies....)

        You gave me a good laugh today, Thanks,
        Gene

        Comment


        • #5
          I would have thought in my mind that shackles be on the back... because to me it would be better over bumps, vehicle in motion... because the spring would compress and axle move rearward, same force as forward travel.
          front shackle I would think would be odd because over bump the axle would move forward, fighting forward travel force....
          My build thread:
          https://www.killbillet.com/forum/20s...at-is-it/page7

          Comment


          • #6
            Originally posted by Burnin#2 View Post
            I would have thought in my mind that shackles be on the back... because to me it would be better over bumps, vehicle in motion... because the spring would compress and axle move rearward, same force as forward travel.
            front shackle I would think would be odd because over bump the axle would move forward, fighting forward travel force....
            That's the way I initially thought as well. Perfect place for something we had on the job trailer wall years ago....

            "I fully realize that I have not succeeded in answering all of your questions.....
            Indeed, I feel I have not answered any of them completely. The answers
            I have found only serve to raise a whole new set of questions, which lead
            to more problems, some of which we weren't even aware were problems.
            To sum it all up... In some ways I feel we are confused as ever, but I
            believe we are confused on a higher level, and about more important things."
            https://www.killbillet.com/forum/30s...the-30-chevyMy 1930 Chevy truck build link:

            Comment


            • #7
              Originally posted by Old Stuff View Post

              That's the way I initially thought as well. Perfect place for something we had on the job trailer wall years ago....

              "I fully realize that I have not succeeded in answering all of your questions.....
              Indeed, I feel I have not answered any of them completely. The answers
              I have found only serve to raise a whole new set of questions, which lead
              to more problems, some of which we weren't even aware were problems.
              To sum it all up... In some ways I feel we are confused as ever, but I
              believe we are confused on a higher level, and about more important things."
              Yep, that pretty much covers it all. LOL!

              I've had a lot of those Dodge 4x4 pickups with the shackle at the front. I can say that none of them were smooth riding, but then I didn't really expect an old 4x4 to ride smoothly. Most of those old Dodge trucks only had 3 leafs in each front spring pack (the heavy duty 1 ton I had only had 4 leafs, and the farmer that had the truck before me told me they added the extra leaf on every corner), those front springs were pretty flat, almost no arch. Even lifting the 1,000lbs snow plow didn't make much difference in the spring arch. They just were not something you would expect a smooth ride from at all.

              I can also tell you I put a ton of miles on those old trucks and never had an issue with the front springs, and more then one hauled a snow plow around all winter for many years, so as for hauling weight, the front shackle works pretty well. Gene

              Comment

              Working...
              X