Found a fiberglass monoleaf. A few questions

[W30olds]

Did a search on car-parts.com and found 2 local yards. Went to the one close to me. They had one out of a 94 SE 4 door. So thankfully I was able to grab the part # off mine and the junkyard one. The one I picked up is a part number higher on the spring rate info list on the old w-body page! Any who it had 100k on the car. Spring looked good. Still has the rubber ends attached and no damage. Thank you for the spring rate chart as well. Very helpful information.

[W30olds]

Spring is a RDJ 17984227. My old spring was a RDH 17984226. Not sure what the first 3 letters mean. Can anyone tell me what the 3 letters mean? Just curious. Thank you.

[Schurkey]

Why do you start an entirely new thread instead of updating the existing thread?  This is the third thread about the SAME TOPIC.  Anyone looking for rear-spring info is going to have to search through two additional threads to find your complete history of this project.

 

 

Any way for a moderator to combine these three threads into one?

http://www.w-body.com/topic/55259-going-to-fix-the-saggy-rear-end/

http://www.w-body.com/topic/55242-changing-rearmono-leaf-spring/

[W30olds]

Damn dude. No reason to get all bent out of shape over it.

[White93z34]

I closed your other 2 threads on this topic, this seemed to be the most current so I left it. Please, you don't need to create a new thread, it makes it very difficult to figure out what you've actually done or not done to your car. 

 

But anyhow, 20-od years on the spring rates don't mean a hell of a lot. I'd wager that there is a better then average chance the spring you got from a 94' is no better then what you have. 

 

The first 3 letters are the spring rate, the digits are GM Part number. Assuming the spring is good (It probably isn't) any difference you'll notice will be a effect of it riding properly rather then a different spring rate. 

[W30olds]

I closed your other 2 threads on this topic, this seemed to be the most current so I left it. Please, you don't need to create a new thread, it makes it very difficult to figure out what you've actually done or not done to your car. 

 

But anyhow, 20-od years on the spring rates don't mean a hell of a lot. I'd wager that there is a better then average chance the spring you got from a 94' is no better then what you have. 

 

The first 3 letters are the spring rate, the digits are GM Part number. Assuming the spring is good (It probably isn't) any difference you'll notice will be a effect of it riding properly rather then a different spring rate. 

 

 

Thanks for the info. I'm hoping the spring is good. No real way to check is there? The spring itself is not damaged from what I can see. Someone I've been talking to some back and forth claims these springs don't tend to wear out? He told me in 35 years of working for his company unless the spring became damaged it usually didn't lose it's load capacity? I dunno. He thinks it's the rear shocks. The company is called LiteFlex LLC and they made monoleaf springs for several auto manufacturers including GM.

[White93z34]

no way to really check till you get it under the car. 

 

From what I've seen is... 92-96-ish cars seem to get it worse then others, of course that's not always a given. My 90' Grand Prix is still fine at 150k, my 92' Z34 was sagging like crazy when I got it at 85k. my 93' Z34 sagged really bad too.

 

You can do rear shocks all you want but might help for a week you'll be back to square one in short order.

[Imp558]

I am unclear as to why strutswould be expected to have an impact on the height of the vehicle. perhaps given the dampening rate when the vehicle is in motion I could almost see them making some difference but not when the vehicle is at rest. There are however big Goofy rubber Springs on the rear end that should make some difference and nobody ever talks about the helper springs

[W30olds]

I believe like most the spring is worn out due to age and mileage. Since I have the new spring here I'm just going to have it put in. It's a birch mount and I've heard good feedback on these springs. Don't believe it will wear out anytime soon. It's solid! Thanks for the input!

[White93z34]

I am unclear as to why strutswould be expected to have an impact on the height of the vehicle. perhaps given the dampening rate when the vehicle is in motion I could almost see them making some difference but not when the vehicle is at rest. There are however big Goofy rubber Springs on the rear end that should make some difference and nobody ever talks about the helper springs

 

I think those are only on Oldsmobiles and maybe Buicks (haven't spent a ton of time on 1g Buicks compared to the other 3 marks so maybe I'm wrong. I'm not entirely sure what their purpose is, I'm guessing its to help soften the ride.

[GnatGoSplat]

I am unclear as to why strutswould be expected to have an impact on the height of the vehicle. perhaps given the dampening rate when the vehicle is in motion I could almost see them making some difference but not when the vehicle is at rest. There are however big Goofy rubber Springs on the rear end that should make some difference and nobody ever talks about the helper springs

 

If there's enough gas charge, struts can affect the height to some degree.  The KYBs I put on mine had about 30-lbs of pressure each (going from memory on that) which seemed to raise unloaded height about a 1/4" to 1/2" compared to the old bad ones.

[Galaxie500XL]

My Cutlass had those..they're called auxiliary springs. After examining the design, the only purpose I was able to determine they served was to ensure consistent contact and pressure between the spring and rear knuckles, which probably would smooth and quiet the ride a bit, especially on rough pavement...but keep in mind, that's my personal theory. I haven't read anyone else saying something similar, so I could be wrong.

[Galaxie500XL]

..I take that back..Chris said pretty much the same thing...must have missed that.

[Imp558]

My 96 had them

[GnatGoSplat]

I agree with the aux springs softening the ride theory.  I think they were a way to get progressive spring rates out of the fiberglass spring.

Removing them increased ride height on my 89 and also made the ride harsher, so it seemed to me that they counter-acted some of the force exerted by the fiberglass spring.

[W30olds]

Hum. I need to check to see if my 95 has them. For some strange reason I believe it does.

[95GS]

No real way to check is there? The spring itself is not damaged from what I can see. Someone I've been talking to some back and forth claims these springs don't tend to wear out? He told me in 35 years of working for his company unless the spring became damaged it usually didn't lose it's load capacity? I dunno.

 

That's a good question I've been pondering too.

One thing I noticed with the replacement junk yard spring I bought (RDJ) - it has a smaller radius of curvature than my

original monoleaf (RLF), though the RDJ is rated much lower on the stiffness scale.

So the replacement may be less tired.

I don't yet have a comparison photo, but intend to post one.

Methinks there's a fair bit of mystery surrounding these leaf springs - - no way to compare them.

Could be another reason some opt for coilovers.

[95GS]

My 96 had them

My 95 Regal has them too.

[W30olds]

That's a good question I've been pondering too.

One thing I noticed with the replacement junk yard spring I bought (RDJ) - it has a smaller radius of curvature than my

original monoleaf (RLF), though the RDJ is rated much lower on the stiffness scale.

So the replacement may be less tired.

I don't yet have a comparison photo, but intend to post one.

Methinks there's a fair bit of mystery surrounding these leaf springs - - no way to compare them.

Could be another reason some opt for coilovers.

So after talking with the guys at flex lite LLC the sales manager found a spring in his inventory. Its the RDM code according to the chart. He's sending it to me free of charge on Monday. He just wants my old spring back for research purposes. How great is that! He is shipping me out a higher arch spring and said it would be the same spring rate, but might raise the rear end up a bit over the stock spring. I'm totally cool with this as hopefully it will level out the stance. I have 2 new KYB G2 shocks sitting in my garage as well. So when my mechanic swaps the spring he's also going to install the new shocks and the addco sway bar I ordered. I checked the chart I found on the old w-body site. The GM part number he's sending is higher up on the stiffness chart than my stock spring. I'm guessing the higher the part number the better it's arch is compared to my stock spring. Hopefully the new spring, shocks and sway bar will fix my saggy rear end and maybe people can ride in the back without having tire scrub in the rear fenderwells.

[95GS]

So after talking with the guys at flex lite LLC the sales manager found a spring in his inventory. Its the RDM code according to the chart. He's sending it to me free of charge on Monday. He just wants my old spring back for research purposes. How great is that! He is shipping me out a higher arch spring and said it would be the same spring rate, but might raise the rear end up a bit over the stock spring. I'm totally cool with this as hopefully it will level out the stance. I have 2 new KYB G2 shocks sitting in my garage as well. So when my mechanic swaps the spring he's also going to install the new shocks and the addco sway bar I ordered. I checked the chart I found on the old w-body site. The GM part number he's sending is higher up on the stiffness chart than my stock spring. I'm guessing the higher the part number the better it's arch is compared to my stock spring. Hopefully the new spring, shocks and sway bar will fix my saggy rear end and maybe people can ride in the back without having tire scrub in the rear fenderwells.

Very interesting about this company. I've been wondering who made these springs & figured it was probably a sub-contractor.

Of course, there could be several companies and even GM itself making these over the years.

 

So Liteflex could be the maker of your original spring and therefore makes sense why they would want to inspect it.

It's a long term, real life (though uncontrolled, undocumented) test sample. If you look closely, you may be able to see the date of manufacture in smaller digits below the spring code - both of mine have this.

 

Supposedly these springs do not 'age' - get weaker with age. But numerous members here claim otherwise...saggy rear end, etc.

It makes me wonder if wear & splitting at the spring ends could be the cause of sag.

(Even though starting to split, mine didn't sag when pulled at 176,000 miles - though admittedly it had a fairly easy (unloaded) life.)

 

I'd thought that this technology was history, except for 'Vettes or small markets, but the Liteflex website says otherwise.

I'll guess that a good part of their quality control is ensuring proper installation and maintenance of the spring ends/contact points.

[W30olds]

Very interesting about this company. I've been wondering who made these springs & figured it was probably a sub-contractor.

Of course, there could be several companies and even GM itself making these over the years.

 

So Liteflex could be the maker of your original spring and therefore makes sense why they would want to inspect it.

It's a long term, real life (though uncontrolled, undocumented) test sample. If you look closely, you may be able to see the date of manufacture in smaller digits below the spring code - both of mine have this.

 

Supposedly these springs do not 'age' - get weaker with age. But numerous members here claim otherwise...saggy rear end, etc.

It makes me wonder if wear & splitting at the spring ends could be the cause of sag.

(Even though starting to split, mine didn't sag when pulled at 176,000 miles - though admittedly it had a fairly easy (unloaded) life.)

 

I'd thought that this technology was history, except for 'Vettes or small markets, but the Liteflex website says otherwise.

I'll guess that a good part of their quality control is ensuring proper installation and maintenance of the spring ends/contact points.

They could be the ones that made these for GM like you said. According to Bob the sales manager they did produce springs for GM for the w-body platform from 93-96. I just know that he's giving me a new spring and seems to know a lot about these fiberglass springs. I'm still not 100% convinced these spring don't wear out over time and mileage, but maybe they don't. According to Bob he told me they rarely lose the load capacity unless they're damaged or have come apart. I dunno. Im just super happy he's doing this for me. I was out today driving the GP with my wife and daughter. Daughter was in the back and anytime I hit a dip in the road the tires scrubbed. So the spring, shocks or both are shot. Be nice when the rear gets repaired next week. Looking forward to being able to cruise through twisty roads again without scrubbing!

[Galaxie500XL]

I agree.  The concept that the spring "never wears out" seems to violate about every law of physics I ever learned in college.  I might buy they last longer than a conventional metal spring, but eventually, they simply must fatigue.

[Imp558]

actually if they "rarely lose the load capacity" I guess I can understand that statement. "load capacity" is pretty vague so as long as the car is physically supported by the spring that can still be a true statement and he said "rarely" so that means there is a failure rate in his eyes.

[95GS]

I agree.  The concept that the spring "never wears out" seems to violate about every law of physics I ever learned in college.  I might buy they last longer than a conventional metal spring, but eventually, they simply must fatigue.

True, everything has a limit. I'd like to see the numbers, the science. Metal fatigue is more commonly understood.

The original designers, and the GM engineers must have studied & tested this model in-depth.

There are 15 grades of the FE3 alone.

Perhaps this tech was previously used in another application or industry.

 

"Never wears out" would need to be defined. It's possible one could develop a material which would last say, twice or triple the life of an average automobile. Then only real diehard enthusiasts would discover the lifespan of such a component.

Many parts get crushed before they wear out. e.g. steering wheels.

 

Wonder how many original w-body monoleafs are still seeing road duty?

[W30olds]

True, everything has a limit. I'd like to see the numbers, the science. Metal fatigue is more commonly understood.

The original designers, and the GM engineers must have studied & tested this model in-depth.

There are 15 grades of the FE3 alone.

Perhaps this tech was previously used in another application or industry.

 

"Never wears out" would need to be defined. It's possible one could develop a material which would last say, twice or triple the life of an average automobile. Then only real diehard enthusiasts would discover the lifespan of such a component.

Many parts get crushed before they wear out. e.g. steering wheels.

 

Wonder how many original w-body monoleafs are still seeing road duty?

I've seen 4 w-body grand prix's 94-96 that must live around me. One is green, one is maroon, the other 2 are white. Miles I have no idea. I'm pondering your idea of original monoleafs still seeing road duty as well. I see these cars ocassionally around me, but not very much. Sometimes I see the ocassional cutlass supreme driving around, but 90% of the time they are beat to shit. Same for the ealier grand prix. 3 of the 5 are super nice. Other 2 are shit wagons.