[KSR74SD455]

Any suggestions on a good spring shop to re-arch and rebuild a pair of leaf springs? Im restoring my SD, one side had 2 broken leafs at the bolt center but the other side is in tact. However, I feel it needs to come apart and be re-banded and re-arched.
thx!

[JLMounce]

I want to try and understand this a little bit better with a little more context.

-You have a 455 SD Trans Am that you are restoring. This obviously is a potentially investment level automobile.
-You have the original leaf springs from the car. One side is broken in half, the other side is not, but both sets are likely the born with set of leaf springs
-You want to repair the intact side and replace the broken side?

If having absolutely correct parts on this car weren't a major concern, I would advise against this. While you can re-arch a set of leaf springs without doing anything to the temper, re-arching one side and building a completely new set for the other side introduces some variables that will make it harder to pin down. While re-arching doesn't necessarily effect the temper of the material, it has no effect on the age of that material and any related working stress it has undergone, especially compared to a brand new component.

It's not impossible, but you may find that the spring rate side to side is off enough to cause some weird driving dynamics. You also may introduce some ride height differences as well. It may create some trial and error to get it right if this is the path you're trying to go down.

How important are having the correct part numbers etc on the springs for this car? I'm not even sure if the leaf packs have part numbers struck on them, I'm not that knowledgeable. If this is a critical concern, my first option would be to try and obtain an NOS set, or a complete set that may be used and re-arch those together.

If the springs themselves don't necessarily have to be a factory part, but can be built and labeled to recreate any factory markings, I would have a set of new springs built for the car, then finished, marked and stamped with any identifiers that are needed. What I would be concerned with is making sure that ride height matched the book. This may mean putting the new set of leafs on, measuring ride height at the factory locations, and altering the arch as necessary to produce the correct height. As far as the where to have this done, reach out to guys that may do local circle track stuff. Anybody doing street stock or similar is likely running leaf springs and they probably have those springs custom made. They'd have a good idea on who could produce what you need.

If it is critical that this car have OEM springs on it, my next choice would be to try and locate NOS parts, or even a set of used OEM springs. Again, through installation and measurement, making any determination on whether or not the spring needs to be re-arched.

In the case of above, you could get one spring and rebuild the other.

Having a brand new spring built and rebuilding the old spring would be my personal final option if no other options presented themselves. I would question at that point if you needed that OEM spring, since you would have one that isn't correct anyhow. At which point I'd have two spring packs built to the specs you need.

[KSR74SD455]

Thanks for the informative reply JL Mounce! Yes this is a low mile (27,000) car that I'm restoring and would like for it to be as correct as possible. I have no intentions of showing it but doesn't change the fact that I'd like for it to be correct if at all possible.
I'm a car guy but know very little about leaf springs. I agree with everything you said and no question that a new and old together could present some challenges. I don't know if the springs are date coded or numbered, if so you cant see them as the car was originally undercoated. From what I've read the steel is better than what can be purchased today but again I really have no idea. In all honesty if I could purchase new and it was equivalent to OEM I'd replace both, save the originals and move along. It would make life a lot easier. I do like your idea of sourcing a matching set originals but probably easier said than done.

Because I want all of the nasty undercoat off, the one that's complete needs to come apart and be re-built with a new bushing. The one that broke is as follows. I believe it is just one of the very short leafs in the stack that broke in half at the center bolt which I read is fairly common. That said maybe that one leaf (which is almost impossible to see alone while mounted in the stack and in the car) can be replaced (even if not original) and the rest of the spring re-used. This would keep them both very similar at the very least. Then when the rear of the car is back in I can check ride height measurements. Maybe they won't need any adjusting at all.

[JLMounce]

I think if it's just one leaf out of the pack, and especially one of the middle leafs, I'd certainly see if it can be salved. That may be the best case.

It is somewhat common. When I replaced the rear end in my 69, both leaf packs were split in half completely once I loosened the U-Bolts. The design traps moisture in that area and they corrode over time.

If you have no intention on having the car judged and are not looking for maximum value at auction of the like, I would probably check into sourcing the correct springs from Eaton. Unless there's a decent shop or two that does leafs in your area (There might be considering you're in Indianapolis) you might be both money and time ahead getting a new set of leafs.

If they sit a little high which is the most likely outcome, you can use a lowering block to get where you need to be.

[KSR74SD455]

Have only located one spring shop here and they're primarily for big trucks but have not been able to get them on the phone yet so maybe I'll get lucky.

Thx again for the info!

KS

[takid455]

Did the SDs have different spring rates? I don't think so. There's nothing SD specific on those cars aside form the engine. The SD or SE in later years just makes a regular part cost more. I have a set of NOS or NORS springs. I'll have to check them out for markings. Ships from NJ.

[kingbuzzo]

I had my leafs re-arched about twenty years ago on my old bird and she sat real high but eventually settled naturally. They were the last shop in town to do that sort of thing back then so good luck with yer quest!

[KSR74SD455]

Originally Posted by takid455

Did the SDs have different spring rates? I don't think so. There's nothing SD specific on those cars aside form the engine. The SD or SE in later years just makes a regular part cost more. I have a set of NOS or NORS springs. I'll have to check them out for markings. Ships from NJ.

It does seem like there could have been some differences since my car has a 3/4" rear sway bar. From what I see the other versions are all smaller. I've really struggled trying to find proper size rear sway bar bushings and drop link bushings for that matter with the exception of Poly after market.

The project is dorment for the next couple of weeks but I'll dig in then.

Thx for the info!

[yahooskidoo]

74 sd springs.

[Joe-Touring]

I have no personal experience with this company, but they were highly regarded on the Jeep Comanche forums. Comanches are pretty rare and have unique leaf springs, lots of very satisfied reviews.

https://www.generalspringkc.com/leaf...maro-firebird/

[Held for Ransom]

The SD/M20 used a 126 lb. rated rear leaf assembly, PJ (481132) +/-.
The SD/M40 used a 103 lb. rating, I believe, PG (480884) +/-.

There were others used when combined with certain options.

[Tim john]

Perhaps reach out to Deaver Spring in California. ? send your good original to match it up and or have a new set made to mimic the original. I have their springs and am super pleased. Very high quality and the ride height is right where I desired. I don't think you would be disappointed, I sure wasn't.

Tim

[KSR74SD455]

Originally Posted by yahooskidoo

74 sd springs.

Cool info!
TY

[KSR74SD455]

Great resource!
Thx Tim

[KSR74SD455]

Great info!
TY