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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 Posted: Jun/01/2018 at 1:48pm
Originally posted by Trader Trader wrote:


- does the rear shackle mount to the frame with a 2 bolt plate?



Yep. The plate is mounted with the eye towards the rear, as shown in the service manual diagram.

Originally posted by Trader Trader wrote:


- did you buy the car new or know if someone tried lowering it?



A previous owner had done something back there. It had the AutoZone lift shackles to compensate for bottomed out springs and the factory shocks.

Originally posted by Trader Trader wrote:


- is this the original differential/spring setup to the car?



I began to question this for a bit, but after more research, I'm fairly sure that this is the original axle. The springs aren't original, of course.

Originally posted by Trader Trader wrote:


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



The Gremlin mounting plate could be reversed like this, though because of the stud spacing, each one would need to be moved to the opposite side of the car from where it originally mounted.

Originally posted by Trader Trader wrote:


- 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 springs that were on my car (which I doubt the previous owner would have made the effort to replace) were 2-1/2" wide, as are my replacements. They also match up with the iso-clamp parts widths, so appear to be correct. All aftermarket replacements I've seen to be available are the same width.

Originally posted by Trader Trader wrote:


The "Revolver Shackle" will likely work but this is a patch.



I checked them out and agree that they would probably work, but at just under $300 a set, they're a pretty expensive band-aid. . .
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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 1:56pm
Originally posted by Airdrie AMX Airdrie AMX wrote:

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.


I was starting to think something along these lines, but am having a little bit of trouble thinking up a good way to block the shackles while lowering the car. If I can't figure that out, I'll go the second-set-of-hands route and see where that gets me.

I'm just finding it really odd that this is happening in the first place; the springs aren't arched to give a lift, and the shackle length is close enough to factory to make any difference negligible. I'm going back to the shop right now to reinstall the leaf packs. Hopefully I'll be able to track down the source of the behavior at the same time.
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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 4:51pm
Alright, so I've got a kind of update - things are different and unchanged.

So here we are with fasteners barely joined. In fact, the shackle mount plate bolts are only on by a couple threads, which was necessary to do to get the reach needed for the shackle bolts, and my shackle bolts don't even have their nuts on. No effective difference from where it was at when I pulled this leaf pack, though the rear is still in the air.



Like the previous attempts I've made at installing these springs, I had to fight like mad to get them to this point. I'm also still unable to get the shackle into a position near the 90°/6 o'clock angle.

That said, a re-read of the section of the TSM covering spring installation allowed me to notice a detail that I had overlooked, mostly because this section isn't helpful at all (due to the order of operations it details, i.e., "Install this thing, then torque it to spec. Install the next thing, torque it.", versus, "don't torque things until the car's on the ground, dummy!").



In case there are any present or future issues with the image displaying, here's a copy of the text:

Originally posted by '78 TSM '78 TSM wrote:

SPRING INSTALLATION
(1) On Gremlin, Concord and AMX insert shackle pins into spring rear eye and rear hanger.
(2) On Pacers, assemble rear hanger bracket and shackle and install in spring rear eye.
(3) On Pacers, position rear hanger bracket on frame side sill and install mounting stud nuts. Tighten nuts to 45 foot-pounds (61.0 Nm) torque.

(4) Position front spring eye in front hanger and install pivot bolt and pivot bolt locknut. Tighten locknut to 110 foot-pounds (149.1 Nm) torque.
(5) Install shackle plate and locknuts on shackle pins. Tighten locknuts to 30 foot-pounds (40.7 Nm) torque.
(6) Install clamp bracket, spring isoclamps, spring plate, and U-bolts.
(7) Install U-bolt locknuts and tighten locknuts to 50 foot-pounds (67.8 Nm) torque.
NOTE: When installing the springs on the axle, be sure the spring center bolt is properly positioned in the clamp bracket and spring plate before tightening the U-bolt locknuts.
(8) Insert shock absorber lower mounting stud in spring plate and install grommet, retainer, and locknut. Tighten locknut to 8 foot-pounds (10.9 Nm) torque.
(9) Remove supports and hydraulic jack and lower car.


So I suppose I can see how you're supposed to get different results going from back to front, but only if I fill in a lot of blanks, like setting the shackles in a rearward position and setting up a block or something to flex the spring against to make it align with (read, "reach") the front hanger. Everything I've seen and read has followed the opposite approach: install the front eye, then attach the shackles.

That leaves me (ha!) with a couple questions:

1- In what order do y'all normally install you leaf packs? Front to back? Back to front?

2- Can anyone confirm the shackle pin spacing for the OE shackles? I took measurements off my Eagle, the shackles of which look to be the same as what was on the '78 AMX I had (sold it before I could remember to get a measurement from it), and 3-3/4" center-to-center seems about right. I don't think the shackle spacing is a problem, but want to confirm since this isn't a stock part.
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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 11:08pm
To answer your question, start with the front spring eye bolt, lay the springs on the floor, roll in the rear end on a jack & get the ubolts on then jack up the rear & install shackles.
Now i can see the pic of the shackles and how much they are angled to the front I can see your struggle, all I can suggest is a bar inbetween the spring & top of the shackle to pry it to the rear as the weight is lowered down. Like I said the jeep I put springs in looked just like that and at the time didn't look like it was going to work. Once the shackles flipped the right way it settled a bit and was fine.
72 amx javelin 401 4spd
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Post Options Post Options   Thanks (0) Thanks(0)   Quote knobbler Quote  Post ReplyReply Direct Link To This Post Posted: Jun/02/2018 at 5:44am
Laying the springs out and attaching the axle makes a lot more sense to me than getting the fronts, then rear of the springs attached and dropping the axle in (and definitely makes a lot more sense than the TSM procedure).

As I've been trying to get the shackles to pop backwards, I've been hitting the end of travel for my pry bar, since I don't have a good spot to use as a fulcrum- the bumper is too high up, there's not a frame rail, and the body edge in the rear is pinch-welded sheet. Regardless, thanks for the advice! What you're saying makes sense, I just need to figure out a good way to execute. I've got a couple ideas for things I can try in the morning. Hopefully one of them work.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote knobbler Quote  Post ReplyReply Direct Link To This Post Posted: Jun/02/2018 at 7:31pm
Little bit of an update: I didn't have the extra hands to help with popping the shackles in the right direction, so I took an approach that wasn't highest on my list of preferences. As a temporary measure, I put a pair of cheap lift shackles on in place of the last set I was using. So far they seem to be doing the trick to fix the shackle's direction of rotation and a few other issues I was having. Being the double-edged sword I expected, they've brought a couple of drawbacks, but I expect those to settle out as I finish getting things torqued down. If they don't, I just found a piece of u-channel in my stock pile that I may be able to use for making a wedge stop to get the correct shackles to rotate like they're supposed to.


UPDATE: Everything's torqued, leaf packs are flattening out, pinion angle looks alright at a glance, and things are looking pretty good. I expect that I should be able to switch over to some sane shackle length in the nearish future. The only thing that's not to my liking is that the rear end is up a fair bit higher than it should be in polite company. Thanks for all y'all's input and help with this!

Edited by knobbler - Jun/02/2018 at 11:20pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote knobbler Quote  Post ReplyReply Direct Link To This Post Posted: Jun/07/2018 at 12:07am
In case someone comes across this thread in the future, some explanation for what happened here can be found in a post towards the bottom of page two of this thread:

http://theamcforum.com/forum/topic94351.html

Turns out that the 8-3/4" arch is what was used for HD springs, and though the item page listed the HD spring SRI number (67-521), it did not mention the springs as being a heavy duty option.

The site where I bought my springs hasn't been functional for a while, but there are other vendors that offer this as a general replacement for '77-78 Gremlins, such as here:

https://www.stengelbros.net/67-521-AMC-Gremlin-Leaf-Spring-Assembly-_p_2905.html

Since other places are apparently lacking this detail, I suspect that the omission is probably just some kind of oversight in product description details from an upstream supplier. Or maybe they're all out to get me. Either way, the leaf packs themselves are just fine. Just be aware that there may be some fitment issues with them because of the increased arch.

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