I have been doing some arm chair racing on how we can get a practical replacement front spring for the AWD Aero. The reason behind this is I replaced the 20 year old rear springs on my van and was surprised by how much they had sagged. I have gained about 4" in clearance for my rear wheels. Well sense the rear springs were sagging that bad, the front ones cannot be much better.

As we all know, there is not a direct replacement for the AWD, just the RWD Aero. The only option was Ford, and those have been discontinued long ago. So I started doing some research and possibly have come up with some substitutes that "might work" that are produced by moog.

Here is a list of Moog springs that they offer. I highlighted the RWD spring info, and what has been reported is the RWD springs do not work for the AWD.




Now Ford does not release spring rate, load, ect, so this is pure conjecture on the AWD. Now if I can get some input on what other AWD vans have, before I proceed, I could make a better educated guess on what to use.

Now going by the RWD, the inside diameter is 4.070" and the control arms for the AWD and the RWD, I believe, are the same. I need to double check tomorrow, but anyway, we will presume they are and find a spring with that relative size. EDIT: The lower control arms are not the same, so the ID is moot.

Now the installed height is 8.75" for the RWD. I measured both sides of my van and they are showing an installed height of 9.75". Now these are 20yo springs so I am not sure how much height they have lost over the years. This is where I would like to get some additional measurements from other members to see where the installed height should be. Right now I am guesstimating around the 10-10.5" is the OE height. But I would like some more measurements to confirm this theory.

Another item I noticed is that I counted 9 coils, the RWD just has 7.28 coils. I would like some confirmation on how many coils the AWD has, it is hard to count with the springs installed. I have seen some people talk about using Ranger springs, but from my research, it looks like one end is Tangential and the other is a pigtail, where OE Aero is Tangential and Square, so without major mods, those will not work.

Then we get into Bar Diameter. RWD is .750 and I have not had a chance to mic mine to see if they are the same size, so if someone could do that, I would appreciate that.

Now we get into the the weight. With the transfer case, Front Driveshaft, axles, dif, I am guesstimating an additional weight of about 600lbs on the front that the springs need to handle. So I estimate that we want springs that can handle at least 2425lbs. When going through the list the closest I can see that has the weight/install height/ and a decent spring rate would be the 584 or 586 spring (I put a tick next to each on the chart.)

Another issue I see is free height. the RWD have about a 3" difference, where with these two options, I have a 6" difference which would mean a lot of compressing to get them to fit. Also these are constant rate where the originals are Variable rate springs. This will affect drive-ability but to what extent, I am not sure until we actually try it out. Another item, the bar size is only 0.718.


So to wrap it up. I would appreciate if you could measure your installed height, Bar Dia, and if possible, free height. Plus any other ideas/thoughts/suggestions would be appreciated.

 

First of all, the front lower control arm for the 4wd van is different from the rwd van. The spring cup is smaller, so there is no chance that the rwd spring will fit.

Rockauto actually lists a front spring for the 4wd Aerostar: Rockwell RC8606. The Moog compatible spring is also numbered 8606. Rockauto does not list specs for the Rockwell RC8606, but they do list the specs for the Moog 8606:

More Information for MOOG 8606

The wire diameter is 0.65", inside diameter 3.5", rate 462 lbs/inch, free height 15.13", installed height 11.0", load at installed height is approximately 1900 pounds. I'm hoping it's the same specs as the Rockwell RC8606, and that Rockauto spec'd the correct replacement.

These springs are normally for the Fox platform cars; 79-93 Mustang, Fairmont, and their variants. I tried to find the stock springs from my 87 Mustang, but I've hidden them too well; I have to make a real effort this weekend.

I haven't gotten under my van to measure the front springs; it will be kind of a hassle to pull those springs to make those measurements, or even trying the Mustang springs on the van. This would only be a fit test, as the stock Mustang springs would be too light (415 lbs/in vs 462 lbs/in) for the van. I do have a set of short Mustang springs with 800 lbs/in rate, but I'm sure that's going to be too short for the van.

 

You are correct XLT, I should have looked at that before posting so those sizes will not work dimension wise, but


Thank you for the mention of the PN from Rock Auto. But my concern is that it is incorrect. Looking at what it says," Front; 4WD; w/o AC"

I am not sure what would make the Canadian models different than the US version? Also the w/o AC concerns me in the weight factor. Well definitely something to consider, thank you for the input XLT.

 

On a parallel track, contact Coil Spring Specialties (or other custom spring shops) to see it they have the application info in their library. If you have a spring in hand, known to be from the target app, they could "in theory" tell you probable rate given the dimensions and wire size. The math is well known. The "in theory" part is because, within the shop you would have to wait until engineering resources can get to you. This track would substitute a shop's experience rather than relying on you or RockA picking a suitable catalog item.

 

The note about non-AC option must have something to do with the load and spring rate. I do not have access to Moog's catalog as you presented, but I'm guessing that the 8606 does not have enough spring rate for the additional weight. It would be nice if we can get that information from a professional wire bender, like Coil Spring Specialties. All of the aftermarket higher-rate springs for the fox body cars are shorter than stock, as they are intended to lower the car, so would not work well for a heavy van.

If I could only find the time to remove the spring in my van to take precise measurements, I could verify those dimensions. I could also see if my Mustang spring would fit the cup in the control arm.

 

Just a quick search. don't know anything about this company

https://www.springworks.com/coil-lea...-auto-buy.html

 

Ok, I finally had a chance to do some more digging in the Moog book. Here is the page with the 8606 spring on it:




The 8606 could be a possibility, but it is only 75lbs heavier than the 2wd, I am not sure about the 11" ride height and smaller dia coils. And as stated below, I am getting an ID of 3.625. Looking at what Moog lists that it fits the early-mid 80s T-Bird and Cougar.

I also did some more measurements today. I am coming up with an ID of 3.625" Coil Dia of .725" and with limited visibility, I am counting 8.5 coils.

I have thought about contacting the companies listed above, but I really don't want to waste their time if I don't buy anything from them.

So far this is all I have been able to accomplish.

 

Now Ford does not release spring rate, load, ect, so this is pure conjecture on the AWD. Now if I can get some input on what other AWD vans have, before I proceed, I could make a better educated guess on what to use.

i have a brousure from ford for my 91 that lists the spring rates.

 

Would love to see this!

 

Some more observations and comments, in no particular order...

* I have very recently had my RWD rear springs out, measured them, compared them to FM/Moog CC841 and observed that, in this case, their specs matched factory. The point is that they are capable of knowing the app and building to it. IOWs, if they had built to your application, they would nail it exactly. Corollary: If you find a parameter in the catalog that doesn't match, then the spring is probably for a different app.

* There are at least a half-dozen spring calculators online. Some are multi-mode, with one mode allowing for you to plug in dimensions and get back spring rate. I suspect these are cheap calculators and that custom spring shops would have better versions that incorporate variable pitch, etc. The rates I was getting back were consistently higher than what Moog lists for my app. The benefit to playing around with the calculators is that you can see how dimensions affect results.

* The key dimensions that affect result are coil diameter, pitch (or count), wire gauge, and free length. Minor params: end style, tempering within norms.

* The Moog catalog shown in this thread is combining/mixing data that is purely a property of the spring, also with data that pertains peculiarly to a target objective. A case in point is "installed height", which is not a property of the spring but a application objective. IOW's the naked spring does not know what its installed height is. Highly related, "load". I suspect that in the catalog, they apply THIS load (in pairs btw) and achieve THIS installed height. I am not accusing Moog obscuring, rather this is standard specs'manship for the industry. Casually interesting, but not really useful.

* As a further example of why not to mix spring data with application data, consider the word "load". To a naked spring, this is fairly clear cut. However, within an particular application the load on the spring is not the same as the load that eventually gets transferred to the ground through the corner wheel. The significant translator is the mathematical leverage due to the control arm. Typically on the front, the spring is inboard from the tire patch and therefore the spring see a higher load than the tire. However, on the Aerostar rear, the axle is between the pivot and the spring and therefore the spring sees a lower load than the tire patch. A small percentage of tire patch load gets transferred from the chassis from the pivot point as unsprung weight. IOW's the "load" spec is open to interpretation based on application.

* Applying Hook's law to the spring dimensions we can come up with an academical/theoretical spring rate. However, the FM/Moog catalog show a VARIABLE pitch for the front RWD (CC850) and so its plausible for the factory front AWD spring to also be a variable pitch app. The reason why I bring this up is that to list a spring rate in a catalog is overly simplistic. The rate is actually variable, dependent on the amount of compression. IOWs, the rate would differ as the spring is compressed. IOWs, you first tell me how far you have compressed the spring, and only then will I tell you what the spring rate is. A graph would tell you all this, but a single number in a catalog doesn't tell the entire story. Its a curve, not a straight line, force vs compression. If one were to report a single number for a variable rate spring, it would be the rate at the installed height for a particular application. For this reason, and for variable pitch springs only, I push the "spring rate" number into the category of application data, not spring data

* If your AWD measured specs differ from the RWD specs, especially in coil diameter, I would assume there was a packaging problem, say trying to get a real axle thru that space. A change in diameter could be accommodated by simultaneously adjusting other spring params, but I start to get skeptical if the spring rate curve differs significantly between AWD and RWD, if there is no further explanation from differences in arm geometry. As an example of adherence to spring rates, check out the difference between long and shorty versions of rear springs. Same rate (!) but the long app achieves a higher load (assumed soaked up by the body) by lengthening the spring by 1 inch.

* It cost me $450 to have a pair of custom springs made through CSS. Roughly 10 times the going rate for FM/Moog production pairs. So it's highly probable that you would not end up buying custom springs. It would be trivial for FM/Moog to produce what you want, but very difficult to get their attention and agreement. I have an inquiry into them on another matter. Crickets, so far. It's a normal corporation, after all. If I do establish a working connection, I will use the opportunity.

Footnote & cavet emptor: These above comments are casual contributions and you may kindly rebuttal. Even though I have an engineering degree, from a world class skool, spring engineering is outside my area.

 

Coil spring design is pretty much tried and trued. The general equation is:

Rate = ( G * WD^4 ) / ( 8 * Coils * CD^3 )

where:

WD = spring wire diameter

CD = average coil diameter

G = torsional modulus of the wire (~12 x 10^6 psi for most spring steels)

You figure out the rate you need by figuring out the load at normal ride height and the compression distance to that height from free length. As you said, the load has to include the corner weight and the leverage from the ground contact point of the tire against where the spring sits along the control arm. Add a small percentage for some safety margin. Then work through the equation to get the other parameters. Some of these are constrained, like the coil diameter and total length, and coil count, so it's pretty easy to optimize these numbers.

I have to believe that a place that has spring making equipment should be able to easily make springs of any specs that you give them. In particular, if they were making replacements, they would have been able to make all the necessary measurements.

 

pm me an email address and i'll send you a pic.i don't know how to post pics here.

 

I wish the mystery gets solved. My ride hight is off by 1 inch on one side 1/2 the other front left different from right. I found a company that sells front spacers for the coil springs there 1/2 aluminum and go on the bottom. The Aerostar has unequal arms so 1/2 spring lift gives almost 2".
Progressive suspension in cal. There $29.00 each. My other Aerostar fourm site has been down for the last 8 hours. I have an article with photos of someone makeing a home made lift kit for there eawd van to run 215-15-75 15 tires. I know I have 6" of ground clearance. I'm trying to build a better vw kombi with an Aerostar van. I would think an awd lifted Aerostar would make a better camper than vw did.
Robert Las Vegas
Icuff4cash@gmail.com

 

Any progress on this issue? I just joined. Trying to find front coil springs for a '95 AWD. I bought the MOOG CC850's before I realized they aren't even close to the same. Starting to search local junkyards...

 

Has anyone considered adding coil-assisted shocks to the Moog 8606 springs to hrlpske up for the lighter loaf rating?