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Shackle inversion problem with new leaf springs

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knobbler View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote knobbler Quote  Post ReplyReply Direct Link To This Post Topic: Shackle inversion problem with new leaf springs
    Posted: May/31/2018 at 5:53am
I've been having some problems with a new pair of leafs that I've installed in my '78 Gremlin, and I'm hoping that someone may be able to point me in the right direction to gets things sorted out.

The issue I'm running into is that the shackles hang 45° pointing forward when the rear is raised, but instead of moving rearward when the vehicle is on the ground, they move forward until they contact the bolt protruding from the inner side of the subframe rail. When fully resting on the suspension like this, the shackles are nearly parallel with the rail.

When I got the springs, I measured from eye to center on each end and the arch depth (A: 23 B: 23 Arch: 8-3/4). Everything checked out fine.

The leaf eye bolts, as well as the top shackle bolt, are a little more than finger tight.

I tried to correct the issue using the crowbar method that people use for unbinding inverted shackles. With the rear lifted, I managed to get them to point straight down, but they returned to the 45° position in a matter of moments.

I understand that new leaf packs need to be broken in, but with the direction of travel with the springs when under load, I don't think it'll be wise to try and break them in until they are at least flattening out instead of curling up. Has anyone else run into this? Any suggestions on how to fix this would be greatly appreciated. Thanks!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: May/31/2018 at 3:50pm
Not personally run into this but look up "Revolver Shackle".  Jeep guy's use these, people on both sides of the fence for climbing/obstacles.  For your situation there should not be any chance of the shackle locking up if you installed them.
I'd take them off once the springs relax enough.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 304-dude Quote  Post ReplyReply Direct Link To This Post Posted: May/31/2018 at 3:54pm
So you raised the rear? Why not use clamp on shock mounts to the axle tubes and use a blank plate to mount the axle?

You probably would do your shocks better that way, than overly extending them.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote knobbler Quote  Post ReplyReply Direct Link To This Post Posted: May/31/2018 at 4:55pm
Trader: Thanks for the tip. I'll look into the revolver shackles you mentioned.

304-dude: My shocks actually aren't installed right now. The issue with the springs is causing the left side to be unable to reach the lower mount, so I've left them off for the time being.

To be clear, I raised the rear up off the ground. I'm not using springs that have any extra arch or anything.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 73hornut Quote  Post ReplyReply Direct Link To This Post Posted: May/31/2018 at 8:08pm
Did you tighten all the bolts with the car raised? The car needs to be on the ground with weight on the springs before fully tightening the bolts.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: May/31/2018 at 8:55pm
Are you sure those are the correct springs???? (and they aren't in backwards LOL)
Seriously, I've never seen a car's shackles pull that far forward - and I've had differentials hanging from the springs while replacing shocks so don't say it's the shocks holding things up............
Somewhere, there's wrong parts or something is put together wrong.

And yes, do not tighten the ends of the springs, front or rear, until the weight of the car is on the springs.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote knobbler Quote  Post ReplyReply Direct Link To This Post Posted: May/31/2018 at 10:39pm
All the fasteners are loose and the springs aren't in backwards (large eye is at the front). These are the correct springs as far as I know, and the measurements I've done have matched with what I understand that they should be.

At this point, I guess I need to go back in and pull things apart to make sure I'm not overlooking anything or that I took incorrect measurements. I'll update y'all with what I find out in a little while here.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote knobbler Quote  Post ReplyReply Direct Link To This Post Posted: Jun/01/2018 at 1:49am
So I just finished pulling the right leaf pack and measured the dimensions twice. The results are 23" for each side, eye to middle of center pin, and the arch is exactly 8-3/4" from the lowest point of the curve to the middle of the spring eyes. To be thorough, and to account for the difference from my setup and the factory, I measured my shackle braces to confirm bolt hole spacing, center to center, and they are at 3-3/4" apart. I'm honestly at a loss here. None of the fasteners were particularly tight, though the front eye bolt was a bit over finger tight.

I'm going to get up in the morning and come back to the shop, finish pulling the other side, and then get things reinstalled. When I do this, I'll be making sure to leave extra play at the fastening points and see if that makes any difference.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Jun/01/2018 at 6:58am
First question since I'm not familiar with the 78 Gremlin
- does the rear shackle mount to the frame with a 2 bolt plate?
- did you buy the car new or know if someone tried lowering it?
- is this the original differential/spring setup to the car?
The reason I'm asking is an easy way to lower the rear end is to reverse the shackle mounting plate - this works in most applications but not all
- AMC changed the Gremlin spring width and it seems the length over the production years but it would take a lot more research to narrow down the specific years.
The "Revolver Shackle" will likely work but this is a patch.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Airdrie AMX Quote  Post ReplyReply Direct Link To This Post Posted: Jun/01/2018 at 10:47am
I ran into this with a 4" lift kit for a jeep cj, once both springs are in lower the car slowly and bar or find a way to pry the shackles back to there normal location while slowly lowering it may take another pair of hands to run the jack. Once the full weight of the car is on them they will settle into position. Now if you take it for a drive and find the shackle flips the opposite way then you have an issue with the springs but I'm sure it will be fine.
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