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Torque spec for rear leaf springs

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cruxop View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cruxop Quote  Post ReplyReply Direct Link To This Post Topic: Torque spec for rear leaf springs
    Posted: Jun/26/2019 at 9:41am
Does anyone know the torque specification for the front eye bolt for the leaf springs in the rear of a 68 AMX? I can find specs in the manual for the rear of the leaf spring (shackles) but can't find anything for the front of the leaf spring. 

Edited by cruxop - Jun/26/2019 at 12:24pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cruxop Quote  Post ReplyReply Direct Link To This Post Posted: Jul/09/2019 at 2:33pm
i'm playing around with this but it seems that if you start torquing the nut to any real level of tightness it starts bending in the frame on the far side where the head of the bolt is. anyone replace leaf springs before? 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: Jul/09/2019 at 3:57pm
Oh heck yes - on three of my current AMCs - I've replaced with new springs on two of them and good used springs on another. I've also replaced springs for various other people.

You have a problem - because the head of the bolt is INSIDE the frame, and the width of the space for the front of the spring is about the same width as the bushing in the front of the spring. In other words, if everything is CORRECT, there's no way to distort that because the wall of the frame and the other side of that pocket clamp against the spring BUSHING center spacer.
You can't crush or distort.
The spring should be a SNUG FIT into that pocket with no real play - there should not be space on either side of the spring bushing center spacer. 
If there is you have the wrong spring or wrong bushing in the spring (or are putting the spring in backwards? IS that even possible!?)

In other words, the CORRECT spring with the CORRECT bushing in the front end fits snug enough into that pocket you can't crush or distort anything. It simply clamps against the bushing center. 
You must use the correct bolt, the correct spring and correct spring bushing - and apparently one of those things is wrong because those parts fit too snug in there to allow anything to crush or bend in.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Steve_P Quote  Post ReplyReply Direct Link To This Post Posted: Jul/12/2019 at 8:02am
We covered this a few weeks ago and nothing has changed since then. Again: you need to fill the additional space with washers if the bushing's sleeve doesn't fill it. I've also had this issue with aftermarket springs.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote cruxop Quote  Post ReplyReply Direct Link To This Post Posted: Yesterday at 1:35pm
thanks guys! The issues are resolved and here's the summary. on my 68 AMX the width for the space on the front was over 3 inches, where factory should have been 3 inches (no clue why). The springs that were on the car when I bought it (20 years ago) had bushings that measured 3.14 inches and fit properly. I am swapping in new springs from Calvert which came with standard 3 inch spacers which didn't fit. I attempted shimming them, but hadn't closed the gap as much as needed, hence it pulling in on the frame as that's the thinnest gauge steel in that assembly. The solution that I ended up going with was Calvert sent me slightly larger bushings that were for a different application that were 3.2 inches, and I ground them down to get to 3.14 and everything fit perfectly. I still haven't found factory specs for the front eye bolt torque however I looked up the torque specs for a 9/16 grade 5 bolt, coarse thread and got 82ft lbs, which is what I'm planning to use. Really appreciate all the support helping figure this out. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote PROSTOCKTOM Quote  Post ReplyReply Direct Link To This Post Posted: Yesterday at 2:37pm
Originally posted by cruxop cruxop wrote:

 I looked up the torque specs for a 9/16 grade 5 bolt, coarse thread and got 82ft lbs, which is what I'm planning to use. out. 
I would strongly suggest that you get some grade 8 bolts and nuts. I sure wouldn't want my springs supported by a grade 5 bolt. If you don't have a local source for them McMaster Carr will be able to take care of you. http://www.mcmaster.com/

Tom
1949 Ford Business Coupe
1969 AMC Rambler Rouge
1974 AMC Hornet Hatckback, Wally Booth Outlaw Nostalgic Pro Stock Race Car Project
1980 Ford Fairmont Futura
1990 Ford F-350 Supercab Dually
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cruxop Quote  Post ReplyReply Direct Link To This Post Posted: 9 hours 6 minutes ago at 8:29am
Hi Tom, looking at the original bolts, it appears that they were grade 2 (see pic) the grade 5 bolt (new) that I used is the one that was provided when I ordered from americanpartsdepot. Is grade 8 critical? 



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Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: 4 hours 59 minutes ago at 12:36pm
Many automotive manufacturers ordered fasteners in bulk without standard markings on them. They may have only had "RC", "AF", ... on them with no grade markings.
Agree with Tom on this. I use grade 8 for all suspension and steering components. The key is to torque or tighten to manufacturer specification for the fastener location and NOT to tighten the fastener to some torque chart value for the fastener.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: 4 hours 43 minutes ago at 12:52pm
Most often the letters indicate the manufacturer......... and have nothing to do with grade. 
Custom made bolts are often not marked - special shoulder bolts and so on made to a company's specs
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