Rear shackle modification

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Craig Burriss

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Back before I moved and my car was torn down to nothing, I ordered a set of the Mopar super sport springs that make the car sit up a little in the rear. When I found out I was moving on very short notice, I threw some 4” Jeep shackles I had laying around on it just so I could get the car on the trailer. The factory ones were bent. Now that I’m starting to drive the car, I don’t like the fact that the rear end sits higher than my Ram. Seeing how they’re just flat pieces of metal with holes in them, is there a reason I shouldn’t just drill more holes in them and chop off the excess? How short can I go with them?

Thanks
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I guess you could, old extended shackles were just straight bar stock. I think the stock length is around 2-3 inches eye to eye. But..... I would just buy a new set from Mancini or PST with new rubber or poly parts. Unless you are cost limited.
 
It’s not the shackles. The factory shackles are also 4” center to center on the pivots.

You can probably shorten them a little, but you’ll run into interference issues before you lower the car all that much. I replaced my rear shackles with spring sliders, which are quite a bit shorter, and that only lowered the car about a 1/2”.

Which super stock springs are those? How many miles are on them? They should settle some as they wear in, but that will take time and miles.
 
The stock shackles are pretty pricey. No reason you cannot modify what you have. I don't think I'd go any shorter than stock though. I don't know what that length is off the top of my head.
 
If the shackles are too short your spring could bind before they go past flat.
 
The stock shackles are pretty pricey. No reason you cannot modify what you have. I don't think I'd go any shorter than stock though. I don't know what that length is off the top of my head.

4” center to center.
 
I'm telling on myself here but I would not be doing a thing to that car concerning shackles. Instead, I'd be trucking straight back to 1973 and would be focusing on a set of chrome custom fender well headers and side pipes instead.
 
It’s not the shackles. The factory shackles are also 4” center to center on the pivots.

You can probably shorten them a little, but you’ll run into interference issues before you lower the car all that much. I replaced my rear shackles with spring sliders, which are quite a bit shorter, and that only lowered the car about a 1/2”.

Which super stock springs are those? How many miles are on them? They should settle some as they wear in, but that will take time and miles.
They are the 3200lb “drag launch” springs. They have probably 20 miles on them because I just started driving the car.
 
They are the 3200lb “drag launch” springs. They have probably 20 miles on them because I just started driving the car.

They'll definitely settle down some. It'll probably take a few months though. I had a set of the 3,600 lb SS springs on my Challenger, which I replaced with regular XHD springs after awhile. Currently I'm using the 3,600 lb SS springs to hold up the back of my Dart and keep it a roller. Even it doesn't sit up as high as your Duster does.

A set of 1" lowering blocks is an easy solution, although you'll need longer U-bolts to go with them. If/when the springs settle down some you can remove the blocks.
 
It’s not the shackles. The factory shackles are also 4” center to center on the pivots.

You can probably shorten them a little, but you’ll run into interference issues before you lower the car all that much. I replaced my rear shackles with spring sliders, which are quite a bit shorter, and that only lowered the car about a 1/2”.

Which super stock springs are those? How many miles are on them? They should settle some as they wear in, but that will take time and miles.
Hey me too but the car is empty, so for ride height I loaded the car with pellet stove bags ,are they noisey ? Haven’t finished the car yet ? I’m thinking they will be .
 
Hey me too but the car is empty, so for ride height I loaded the car with pellet stove bags ,are they noisey ? Haven’t finished the car yet ? I’m thinking they will be .

The sliders? When I first installed them I heard them a few times when I was trying to listen to see if I could hear them. So I wouldn't exactly say they're noisy. But to be honest most of the time it's hard to hear anything over my exhaust, my stereo, and the ringing in my ears. :D
 
They'll definitely settle down some. It'll probably take a few months though. I had a set of the 3,600 lb SS springs on my Challenger, which I replaced with regular XHD springs after awhile. Currently I'm using the 3,600 lb SS springs to hold up the back of my Dart and keep it a roller. Even it doesn't sit up as high as your Duster does.

A set of 1" lowering blocks is an easy solution, although you'll need longer U-bolts to go with them. If/when the springs settle down some you can remove the blocks.
I like this solution. Blocks are cheap and my Ubolts are already about an inch too long.
 
I like this solution. Blocks are cheap and my Ubolts are already about an inch too long.

Perfect!

You're not the first person to run SS springs with lowering blocks. People have had them de-arched as well, although that requires taking them off and hauling them to a spring shop. Since yours are brand new they will definitely settle, some settle quite a bit. The XHD's I put on my Challenger settled a couple of inches in the first 6 months. So I would just run blocks in the meantime. If they settle down too much you can pull the blocks later. If not, the blocks don't really hurt anything as long as they aren't super tall.
 
Isn't there lowering front spring mounts?

Yes, there are. And thank you for reminding me because my Dart has them on it. They have two mounting holes for the spring eye, the higher one lowers the car about 1". Which is probably why my Dart doesn't sit as high the OP's car. Oops.:rolleyes:

They do change the spring geometry though, so you have to consider that if you're using the SS spring for the intended purpose of increasing launch grip.
 
The sliders? When I first installed them I heard them a few times when I was trying to listen to see if I could hear them. So I wouldn't exactly say they're noisy. But to be honest most of the time it's hard to hear anything over my exhaust, my stereo, and the ringing in my ears. :D
:thumbsup: Good news I’m deaf too
 
I replaced my rear shackles with spring sliders, which are quite a bit shorter, and that only lowered the car about a 1/2”.
I wouldn't exactly say they're noisy.
I have been on the A-Bodies forum recently, mainly checking on progress on moselyme and his F&B modded Weiand 6bbl intake and to get information on the intake, since I just got one.
I have just ordered Calvert split mono leaf springs and Assassin traction bars, and I got the Calvert sliders to attach the rear spring mount, so I'm glad to hear...that you don't really hear them. :)
I wanted the sliders as soon as I saw a video of them in operation.
I did select the +1" ride height springs, thinking that would offset the 1/2" drop of the sliders, and to keep the narrowest part of the inverted U of the rear fenderwells away from the top of the rear tire, so I can get the widest tire possible with the stock leaf spring location.
So far, on my 70 Roadrunner, I have been able to get a 315/35/17 to fit with zero rubbing, perfectly centered, with a 5" backspacing, but I want to try a taller sidewall for a better launch, without a narrower tread, like a 345/45/17.
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