Commentary on Mopar XHD springs.

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1968FormulaS340

1968FormulaS340

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Commentary on Mopar XHD springs.

In the last month or so we have had a bunch of rear spring questions.

dmoore had Mopar XHD springs on his Duster. Looking at his car it sat higher than some of the cars I have seen with SS springs.

My car with Mopar XHD springs sat much lower even before I flipped the front hangers.

Others with Mopar XHD springs have various ride heights that I do not feel are attributed to body style or mobs.


So this is my opinion.....

If you buy Mopar Brand XHD springs you don't know what you will get. I must assume Mopar is using several spring manufactures.
 
And or quality control is poor .
Also these springs have to settle in I think .
Initially they jack the rear up like a stink bug .
After a few days to a week the ride height settles and looks more correct.
IMHO
 
Sure it could be....... But if you go through all the threads you will see cars of the same body style sitting all over the place with these springs. At least a 2" variation.

Most are full bodied street cars with similar mods and I would bet similar weight. I doubt weight is playing that big of a part in rear hight for this particular brand of spring.

I would put my money on poor quality/tolerance control and/or supplier variations.


I'm just trying to inform, not start a debate. For those that are looking for new springs, again in my opinion.... You will have a better chance of getting what you are looking for from the after-market.
 
I think we can all agree that all Mopar XHD springs are not the same.

I'm really pleased with the ride height of my two left springs but it did cost me a right spring as well.

All 3 of my springs have the MP part #'s painted on them along with JRS (http://www.johnrspring.com/) so this is where mine came from.
 
Of course I can't know what others are using, but my XHD 340 replacements are asymmetrical (different number and length of leaves). Mopar originally did that to counteract torque reaction and plant the right rear tire. That alone can and did cause the rear of the car to sit uneven in my case. A simple torsion bar adjustment leveled the car side to side and raised the front up enough to give the same tire to fender lip gap all the way around alleviating any suggestion of the stink bug phenomenon.
 
Also it could be that some of the cars you were looking at had a different amount of fuel. A galon of gas wieghs about 8 lbs. A full tank will sit lower. just my .02
 
twofosho said:
Of course I can't know what others are using, but my XHD 340 replacements are asymmetrical (different number and length of leaves). Mopar originally did that to counteract torque reaction and plant the right rear tire. That alone can and did cause the rear of the car to sit uneven in my case. A simple torsion bar adjustment leveled the car side to side and raised the front up enough to give the same tire to fender lip gap all the way around alleviating any suggestion of the stink bug phenomenon.
Click to expand...

Unless I am very much mistaken, the XHD springs are not the same as SS springs, which is what you are describing. The later are really drag only springs, while XHD is just higher rate and should be the same number of leaves right to left.

If you are compensating for unevenness of your leafs by adjusting your TBs, and you are running this on the street - well - that does not sound like a good plan to me ... but it's your nickel.
 
Just to add my own 2cents about leafs ...

Back in about 1990 I purchaced a set from Year1 - 340 HD set. They told me who actually formed them (their source), though I can't remember who it was I seem to recall is was some company in the Detroit area, not that it matters now. I still have these on my car and like the way they sit (surprisingly after almost 20 years that aspect of them has not changed much at all and they are very stock looking (see my garage or whatever for pix). My one bone to pick with them is that they open and tend to loose some of the plastic "quieters" (whatever you call them), because the binder straps are not all that tight.

I bought another set for my no-longer-owned '75 Dart Sport that were not even supposedly HD 340 - If I recall, and I am pretty sure about it - they have 1 fewer leaves on each side. Yet they always rode higher than the 340 car for all the years I'd owned them and felt just about as firm. The quality was better too and never had that problem with the bindings loosening and such. I bought that set at an Englishtown swap meet back about 10 years ago.

So my point is, the number of leaves, the arch, and the company all make a big difference. If you can, get them in person where you see them before you pay.
 
dartley said:
Unless I am very much mistaken, the XHD springs are not the same as SS springs, which is what you are describing. The later are really drag only springs, while XHD is just higher rate and should be the same number of leaves right to left.

If you are compensating for unevenness of your leafs by adjusting your TBs, and you are running this on the street - well - that does not sound like a good plan to me ... but it's your nickel.
Click to expand...

You are mistaken,and twofosho is dead on with his assesment on the 340 xhd springs. Have the same pair on my Dart.There are two different part #'s. The right side does sit higher on them,and adjusting torsion bars to your perticular taste is a common practice.
(Rear right high,raise front left). Guys back in the day use to adjust the torsion bars with the driver in the car.When the driver would get out of the car, the front left seemed a bit high depending on their weight.
 
twofosho said:
Of course I can't know what others are using, but my XHD 340 replacements are asymmetrical (different number and length of leaves). Mopar originally did that to counteract torque reaction and plant the right rear tire. That alone can and did cause the rear of the car to sit uneven in my case. A simple torsion bar adjustment leveled the car side to side and raised the front up enough to give the same tire to fender lip gap all the way around alleviating any suggestion of the stink bug phenomenon.
Click to expand...

Johnny Dart said:
You are mistaken,and twofosho is dead on with his assesment on the 340 xhd springs. Have the same pair on my Dart.There are two different part #'s. The right side does sit higher on them,and adjusting torsion bars to your perticular taste is a common practice.
(Rear right high,raise front left). Guys back in the day use to adjust the torsion bars with the driver in the car.When the driver would get out of the car, the front left seemed a bit high depending on their weight.
Click to expand...


No I am not wrong - you are. The XHD springs are biased, but have the same number of leafs right to left - they have diff part #s because they are diff left to right. The SS springs have a different number of leafs left to right. I know - I have a pair in my garage.

http://www.jegs.com/p/Mopar-Performance/Mopar-Performance-Leaf-Springs/747047/10002/-1
 
dartley said:
No I am not wrong - you are. The XHD springs are biased, but have the same number of leafs right to left - they have diff part #s because they are diff left to right. The SS springs have a different number of leafs left to right. I know - I have a pair in my garage.

http://www.jegs.com/p/Mopar-Performance/Mopar-Performance-Leaf-Springs/747047/10002/-1
Click to expand...

So explain to me where I am wrong.

As I stated in my post:
The right side sits higher with the 340 springs.
People adjusting tb's to their taste is common practice.

Never said anything about # of leafs. :read2:
 
dartley said:
If you are compensating for unevenness of your leafs by adjusting your TBs, and you are running this on the street - well - that does not sound like a good plan to me ... but it's your nickel.
Click to expand...

Why? How do you know the factory didn't do the same thing, how much cross weight is incurred by doing that, what effects that would have on handling, and that the torsions were equally loaded in the first place?
 
375inStroke said:
Why? How do you know the factory didn't do the same thing, how much cross weight is incurred by doing that, what effects that would have on handling, and that the torsions were equally loaded in the first place?
Click to expand...

I don't know - I said it did not "sound like a good plan". When I say that, I mean that I respectfully suggest that you check into it. But the "it's your nickel" part was also my attempt at respectfully acknowledging that it is up to you. IOW - what are the alignment specs for the car that came with these springs (factory 340 that is). If they show what you are doing to be correct then that settles it I would say. As to the SS springs - I'd suggest reading the old Direct Connect chassis manual for that - I actually have one but not with me at work. I don't know where else you'd get specs on that except to ask someone who knows how to set them up. But those were designed for drag racing only. If you like the look (I had them on my Duster once myself) fine, but I would not expect good road manners from them.
 
This is ridiculous - just re-read the posts:

I said: "Unless I am very much mistaken, the XHD springs are not the same as SS springs".

You said: "You are mistaken,and twofosho is dead on with his assesment on the 340 xhd springs."

If we are talking at cross-purposes then that's something else. I made a comment - and it certainly was not dogmatic, and you told me I was wrong. I was already pretty sure I wasn't, but I didn't say so until I re-checked. I posted a link. The part that I thought we disagreed on was about the difference between XHD and SS springs, not about the TB loads; I was not telling you that you were wrong about that, only that I suggested you might be.
 
Why are the Jegs XHD springs for A-body 64-75 twice as much as the others? I am wanting a set but pay twice as much? DAMMMMMMNNNN!!!!
 
dartley said:
Unless I am very much mistaken, the XHD springs are not the same as SS springs, which is what you are describing. The later are really drag only springs, while XHD is just higher rate and should be the same number of leaves right to left.

If you are compensating for unevenness of your leafs by adjusting your TBs, and you are running this on the street - well - that does not sound like a good plan to me ... but it's your nickel.
Click to expand...

Looking back at your post,the thing that I didnt agree with is the adjusting of the TB's (your nickel).Like I said,it is common practice to adjust to personel preference.
As far as the springs,you are right,they are different. 8)
 
dartley said:
Unless I am very much mistaken, the XHD springs are not the same as SS springs, which is what you are describing. The later are really drag only springs, while XHD is just higher rate and should be the same number of leaves right to left.

If you are compensating for unevenness of your leafs by adjusting your TBs, and you are running this on the street - well - that does not sound like a good plan to me ... but it's your nickel.
Click to expand...

I also have a set of the XHD springs and they do in fact have a different number of leafs with varied lengths per side similar (but not exactly the same) to the SS springs just like twofosho described. They also produced the "stinkbug" effect on my Cuda and I had to adjust the left torsion bar tighter to make it set level.
 
Johnny Dart said:
Looking back at your post,the thing that I didnt agree with is the adjusting of the TB's (your nickel).Like I said,it is common practice to adjust to personel preference.
As far as the springs,you are right,they are different. 8)
Click to expand...

Fair enough.
 
Johnny Dart said:
Looking back at your post,the thing that I didnt agree with is the adjusting of the TB's (your nickel).Like I said,it is common practice to adjust to personel preference.
As far as the springs,you are right,they are different. 8)
Click to expand...

fishy68 said:
I also have a set of the XHD springs and they do in fact have a different number of leafs with varied lengths per side similar (but not exactly the same) to the SS springs just like twofosho described. They also produced the "stinkbug" effect on my Cuda and I had to adjust the left torsion bar tighter to make it set level.
Click to expand...

Then those XHD springs are not true 340 HD replacements. I can't account for all the different possibilities that exist now a days (as I mentioned in another post / possibly in another thread - I'm older and so can opt out via memory pblms :) - that I bought two different pairs from two different companies over a span of about 20 years, and one set was supposedly 340 HD, and indeed looks and feels like it; while another set was supposedly HD /6->318 and had more arch, higher stance and about the same stiffness, but with one fewer leaf in each side if I remember correctly. These later ones seemed to be made slightly better. Point is, anyone can make anything and call it anything. But HD 340 springs are same leaf count per side.

~Bill
 
Your right. The factory 340HD springs were the same number and leafs per side. The XHD springs are not and from what I've seen were used only on big block cars. At least that's all I ever saw them on back in the day. Nevertheless wasn't the Mopar XHD springs what the topic was about? Not the 340HD springs?
 
fishy68 said:
Your right. The factory 340HD springs were the same number and leafs per side. The XHD springs are not and from what I've seen were used only on big block cars. At least that's all I ever saw them on back in the day. Nevertheless wasn't the Mopar XHD springs what the topic was about? Not the 340HD springs?
Click to expand...

Yes, but that link that I posted on the prior page - and any others I could find for what are being sold as XHD - define them as: "XHD Leaf Spring - Original Equipment
These extra heavy-duty springs are just like the bias design production springs that were stock items on 1968-72 A-body vehicles with 340 high performance engines ... ".

So ... dats da angle I wuz cum'n frum ;-)
 
Point is, anyone can make anything and call it anything. But HD 340 springs are same leaf count per side.

~Bill[/QUOTE]

I bought a set of XHD original equipment Mopar 340 springs (P4510268,P4510269), and wish I didnt.
Thought the car would sit flat with them,but the right rear sits higher ala S/S springs. Plus these things are redicously overpriced,basically buying the Mopar part #. Could have got the same spring from JR Spring (where they are made) for much less. I believe they make the springs for pretty much everybody.

Favorite springs of all time were from JC Whitney,stock replacement models.
 
Johnny Dart said:
Point is, anyone can make anything and call it anything. But HD 340 springs are same leaf count per side.

~Bill
Click to expand...

I bought a set of XHD original equipment Mopar 340 springs (P4510268,P4510269), and wish I didnt.
Thought the car would sit flat with them,but the right rear sits higher ala S/S springs. Plus these things are redicously overpriced,basically buying the Mopar part #. Could have got the same spring from JR Spring (where they are made) for much less. I believe they make the springs for pretty much everybody.

Favorite springs of all time were from JC Whitney,stock replacement models.[/QUOTE]


Wow, that's something.
 
FWIW, my 68 Barracuda had three options one of which was heavy duty suspension (\6 car). It had identical springs on each side with 6 leafs each. They were tapped out and the rear was sagging (needed longer shakles to keep the car level). I purchased a set of Mancini XHD springs to replace them. They are 5 leafs per side, but if you measure the thickness of the spring pack at the axle the 5 leaf set was about 0.030" thicker than the 6 leaf set. Each spring leaf was a little thicker than the ones in the 6 leaf set.

Anyway, when installed the rear sat higher than I liked (yes I installed correct shackles), but within 500 miles the rear settled and it has been the same now for about 20k miles. Here is a picture of the rear of my car.

IMG_0810.jpg
 
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