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Discussion Starter · #1 ·
I’ve been reading a lot on the forum and google in general about springs front and rear for my 66.

Rear springs: seems that different companies, dealers focus on different spring aspects to sell there wears.

Question; generally I’m looking at either the NPD - Eaton 5560-60. 138 lb spring with 1 inch drop over factory or the Scott Drake SCD-C5ZZ-5560-4ME. This one I’ve seen described as 139 or 175 lb and being a 4 1/2 leaf mid eye spring.

Question is Eaton doesn’t seem to qualify things by number of leafs or eye attachment location. Are these two items basically the same item, or, ...,??? If different is one better?

Front springs: similar thing looking at Scott Drake SCD C5ZZ-5310-E and NPD part number 5310-1A. Both are described as GT springs with a 1 inch drop from stock height. NPD is also described as a 480 lb spring rate.

Again are these basically the same item?, or,???
 

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Only the letters and words used to describe them are similar. Like a hamburger from Sonic or Del Friscos.
Only get SD springs to save money(like me), they seem fine for now, Hecho in Indio. If you want to go even a peg lower think about grabAtracks.
Eaton actually makes about a dozen+ springs for our cars, too many for the vendors to carry them all. https://www.eatondetroitspring.com/ If you go there and can make a choice then search around for that part#. Then you might find them from a vendor like NPD for less than their direct price.
NPD is always good to call. Receptive to calls and give advice freely. They will give you the straight dope.
 

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I babble on a lot about this stuff. I'll give you my thoughts for what it's worth. I believe for the most part Ford really had their poop together with the Mustang GT except for alignment and not having the Arning drop but that could be for other reasons. Anyway we know how successful the Mustang was with the Arning drop, good alignment. It's a tried and true set.up we all know. Why reinvent the wheel?

I'm going to say use the SD GT coils and Eaton GT spec leaf springs at 118 pounds per inch. I'm running the 600 pound per inch coils but I have a bearing suspension and I need somewhere near that amount due to the lack of binding from rubber bushings. I'm using the SD mid eye 4.5 leaf rated at 175 pounds. Why? I got a good deal, I needed springs and don't have the money right now. So they were the right springs for me under the circumstances. However I do like them and I am happy with them. But how does the SD ratings compare to Eaton? Who knows? I take the SD ratings with a grain of salt and take Eaton as the gold standard. Eaton's are USA made with USA steel. They were the supplier to Ford, have the blue prints from Ford. SD are made in India from a different grade of steel. It's like comparing apples to oranges. I must say though the Indian springs are made pretty nice. I'd take them over Chinese.
 

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Spammer Hammer
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I won’t say they’re apples to apples, only because I don’t own a set of Eaton springs, but I will agree with Tom in that the India springs (SD) seem pretty nice. I have four own track sessions on mine with Del-A-Lum bushings and I’m pretty happy with them. There’s always room for improvement. In my case, more so with the driver.
 

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I’ve been reading a lot on the forum and google in general about springs front and rear for my 66.

Rear springs: seems that different companies, dealers focus on different spring aspects to sell there wears.

Question; generally I’m looking at either the NPD - Eaton 5560-60. 138 lb spring with 1 inch drop over factory or the Scott Drake SCD-C5ZZ-5560-4ME. This one I’ve seen described as 139 or 175 lb and being a 4 1/2 leaf mid eye spring.

Question is Eaton doesn’t seem to qualify things by number of leafs or eye attachment location. Are these two items basically the same item, or, ...,??? If different is one better?

Front springs: similar thing looking at Scott Drake SCD C5ZZ-5310-E and NPD part number 5310-1A. Both are described as GT springs with a 1 inch drop from stock height. NPD is also described as a 480 lb spring rate.

Again are these basically the same item?, or,???
We (NPD) not only carry every single original Eaton leaf spring application, we keep every one of them in-stock. No exceptions. We don't dance around with our in-stock inventory ;) .

5560-60 is Eaton ML 1435-1-138 It is a standard-eye spring, 1-inch-lowering from stock-spec, 138 lb.. We have plenty in-stock.

Eatons are American-Made, using proper 5160 spring steel, which is a big deal compared to most offshore springs. If you have any other questions on spec or construction, feel free to contact Eaton direct. But if you order direct, know that it'll be more expensive. I've been arm-wrestling with Mike over the retails for years now ;) (I love Mike Eaton, great guy, just FWIW).

Our 5310-1A lowering springs are likewise American-Made (I won't disclose manufacturer, because these are exclusive/proprietary to us) by a top-notch manufacturer. We've been selling these springs for decades now, so they're tried-and-true. 480 lb. rate, 1-inch lowering, metallic gray powder-coated.

I do not profess to be a road-racer or chassis guru, so I won't elaborate on whether 480 or 550 or 600 lbs is what you should be running up front. I just know that over the years we've received many happy reviews with the 480's. We have plenty of the 5310-1A's in-stock as well.

Rick
NPD
 

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Discussion Starter · #10 ·
Our 5310-1A lowering springs are likewise American-Made (I won't disclose manufacturer, because these are exclusive/proprietary to us) by a top-notch manufacturer. We've been selling these springs for decades now, so they're tried-and-true. 480 lb. rate, 1-inch lowering, metallic gray powder-coated.

Rick
NPD
Rick, thanks for the response.

On the 5310-1A can you share what grade of steel they are manufactured with?

Thanks,
Harlon
 

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Discussion Starter · #13 ·
Went in for inspection this morning. Everything passed once again.:surprise:

I wanted to add a pick of my rear leafs. Note the helper spring that’s been added and the funky tow package rear buckle.

With 195 70R14s my rear ride height is at 27 inches. Wonder how it’s going to look with new springs?
 

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Went in for inspection this morning. Everything passed once again.:surprise:

I wanted to add a pick of my rear leafs. Note the helper spring that’s been added and the funky tow package rear buckle.
You need to replace your shackles with stock height ones.
 

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Discussion Starter · #16 ·
You need to replace your shackles with stock height ones.
There’s soooooo much I need to do! Just not exactly sure where to start.

Not sure exactly what’s going on with those shackles. What’s not visible is that under the helper leaf the left spring has a broken bottom leaf. Not sure if the idea with the extra long shackles was to compensate for the worn out springs or something else. Cause it’s raised up higher than stock.

Story of my life, start down a path, start to formulate a plan of action, put together a target list of parts to complete said plan of action, put together an order to acquire said parts, and, reach my budget threshold before I get to the end of the parts list.

This winter I want to replace my springs and shocks on all four corners and install roller perches and a new front sway bar. I had gotten the springs, all the hardware and the front sway bar and checked my cart and was like oh I’m good. Then remembered, oops, got to add another $400 to that for shocks.

Low budget is better than no budget, but jeez, sometimes I wish my dad hadn’t taught me that when you buy something you should buy the best quality you can afford so you don’t have to buy it twice.
 
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