Rear Springs

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Animal Lawyer

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Does anyone have an opinion regarding the qualitative differences between the Eaton Detroit HD rear springs and the Summit Racing 5 leaf springs. I have read Eaton's blurb about the quality steel they use and its durability, but, at more than twice the price of the Summit 5 leaf springs, plus shipping, it seems excessive. I'm running a '73 vert daily driver with 351c ~400 hp, T5, 3.25 9" posi rear (anyone have a 3.73 posi rear center section they want to sell at a reasonable price?). If anyone has an opinion regarding the two different springs and a basis for choosing one over the other (other than price) I would appreciate the input. Right now I'm leaning towards the Summit 5 leaf springs with either Koni's or Bilsteins.
 
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I bought a set of Eaton Detroit rear springs and that is what is on the car now, happy with them, but for the price I paid I should be happy. From what I have been able to gather the main issue with the less expensive springs is that they make a few sets of them for what are a ton of different applications. What this will impact the most if your ride height. Your car could end up too high or too low. With the Eaton Springs, they make them specifically for each individual application, they all are a little different to make sure that the ride and your ride height is what Ford intended. I know that there are some people that have had bad luck with some of the off brand leaf springs coming from overseas, but in reality they seem to be few and far between. The front coil spring seems to be much more critical, there are a ton of people with issues with the overseas front springs, mostly because their cars sit way too high. I bought some Moog front springs, I think the part number was 8356, and the car is about an inch too high in the front. If I were to do it again I would buy the Eaton Detroit springs for the front. From what I can see for front springs definitely get the Eaton ones, and for the rears you can probably get some of the less expensive stuff.

Here is the deal, if you want it to be perfect, or at least the way Ford intended, Eaton Detroit is probably the only way you will get that. If you are willing to have some difference in ride height and ride, then the off shore stuff will work. Most of the time there are workarounds to get your ride height where you want it to be if the springs you buy will not get you what you want.
 
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At the end of the day, it's your car your way, but from my experience, I'd for sure go with Eaton's springs. It's no "blurd" it's fact. For your car, probably the 138lb spring rate would be good. I put the 153 lb Boss springs in my Mach and they are pretty stiff. You can always call Eaton and ask their suggestion based on what YOU want out of it. I doubt Summit can tell you anything about the ones they sell other than they are 5 leaf springs. You get what you pay for.
When I was researching springs to replace those Grab-A-Track things I bought and wasted my money on, the only two companies that came even close to providing spec info were Dayton and Eaton. Anything made off-shore I'd steer clear of. From what I was able to find out, but without confirmation, some (so called) springs are made from a semi hard tool steel called 4140 Pre-Treat. Not a good steel for springs at all, but the off-shore companies don't care as long as they get your money.
Do your due diligence, put your money where it's needed.
 
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I bought a set of Eaton Detroit rear springs and that is what is on the car now, happy with them, but for the price I paid I should be happy. From what I have been able to gather the main issue with the less expensive springs is that they make a few sets of them for what are a ton of different applications. What this will impact the most if your ride height. Your car could end up too high or too low. With the Eaton Springs, they make them specifically for each individual application, they all are a little different to make sure that the ride and your ride height is what Ford intended. I know that there are some people that have had bad luck with some of the off brand leaf springs coming from overseas, but in reality they seem to be few and far between. The front coil spring seems to be much more critical, there are a ton of people with issues with the overseas front springs, mostly because their cars sit way too high. I bought some Moog front springs, I think the part number was 8356, and the car is about an inch too high in the front. If I were to do it again I would buy the Eaton Detroit springs for the front. From what I can see for front springs definitely get the Eaton ones, and for the rears you can probably get some of the less expensive stuff.

Here is the deal, if you want it to be perfect, or at least the way Ford intended, Eaton Detroit is probably the only way you will get that. If you are willing to have some difference in ride height and ride, then the off shore stuff will work. Most of the time there are workarounds to get your ride height where you want it to be if the springs you buy will not get you what you want.
GOOD post. My thoughts exactly. You may have read my post on front springs. I bought what turned out to be Scott Drake's front end "kit" and the springs were nearly 2" too high. I put the original and still good factory springs back in without an issues.
 

Grandmas73

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Agree with 71ProjectJunk. While I have a 73 vert my drive train is different but the Eaton springs I put in I am very happy with the stance and quality of material. I’m working on the ride quality meaning the original specs were for hydraulic shocks so my cheap gas shocks were not a good choice. Once I get the Eaton recommended QA1s I should be happy. My two cents
PS Eaton actually recommended me AWAY from changing my coils. They explained a few ways to test and then finally asked if I liked the height, which I did, they said save your money. When is the last time someone said keep your money?
 

Hemikiller

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IMO, since you are running the car as a daily driver, you need the higher quality Eaton springs. The import bargain brands are fine for the masses that drive their cars a couple hundred miles per year. Since you have a Q-code, it came with Competition Suspension and the 138lb springs. Any Mustang I've ridden in that had 5 leaf springs, rode horribly. A convertible will only make matters worse.

Regarding front coil springs, the owners are as much or more to blame as the suppliers. Many throw on a set of headers, an aluminum intake & water pump, delete all the AC stuff, which takes 75-200lbs off the front end, then wonder why the car rides high like an old school gasser.
 
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