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Discussion Starter #1
New memeber looking for some advise and info. Looking to upgrade rear control arms or bushings. 1990 gt. Its a daily driver. A few mods done. Upper and lower intake. 70mm throttle body. CAI. Headers to full exhaust. 373 gears. Tires are 245/45/17. Rear lower oval bushings are worn out. Cant find stock replacements. Don't think I need to go tubular arms but would like some kind of upgrade. Quick search I found polyurethane bushings kits for stock arms. Waste of time? Whats my best value? Looking to replace rear springs also. Sagging a little in the rear. Should I go with variable rate or constant rate springs? Any suggestions would be great thanks
 

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Are we talking about the lower, upper of both sets of arms? If upper, only use a stock type rubber bushed replacement. If the lowers, look at the MM pieces especially the adjustable height arms. These allow you to fine tune the rear ride height. As for springs, you should use a matching F/R set, such as H&R, so the spring rates will be balanced.
 

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Discussion Starter #4
Just looking at doing the lowers. Local speed shop has a set of poly bushings(prothane brand i think) for really cheap. They ordered them for someone and never got picked up. I'm somewhat on a budget. Upper arms and bushings are still perfect. Would the poly be ok in just the lower arms? And i found a moog set of just rear springs online for a good deal. Front springs were replaced a few years ago with the same brand moog.
 

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Hard to beat the MM arms. The way Ford did the rear arms, going poly is not going to give you the benefits you think. If you went stock springs up front, stick w/ Moog replacements then in the rear.
 

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Discussion Starter #6
Hard to beat the MM arms. The way Ford did the rear arms, going poly is not going to give you the benefits you think. If you went stock springs up front, stick w/ Moog replacements then in the rear.
Hard to beat the MM arms. The way Ford did the rear arms, going poly is not going to give you the benefits you think. If you went stock springs up front, stick w/ Moog replacements then in the rear.
Would love to go with MM for everything but its just not in the budget right now. Not really looking for a benefit from the poly. I just need the oval bushings replaced in the lower arms. And cant find replacements anywhere. I can get the full poly kit for the rear arms for$50.
 

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New memeber looking for some advise and info. Looking to upgrade rear control arms or bushings. 1990 gt. Its a daily driver. A few mods done. Upper and lower intake. 70mm throttle body. CAI. Headers to full exhaust. 373 gears. Tires are 245/45/17. Rear lower oval bushings are worn out. Cant find stock replacements. Don't think I need to go tubular arms but would like some kind of upgrade. Quick search I found polyurethane bushings kits for stock arms. Waste of time? Whats my best value? Looking to replace rear springs also. Sagging a little in the rear. Should I go with variable rate or constant rate springs? Any suggestions would be great thanks
Funny how things come in waves.
Several years ago the factory style rubber replacement bushings were impossible to find.
About 3 years ago they were everywhere, and here we are again with them impossible to find.

My suggestion is to buy the poly bushings and swap them into the lowers, but go ahead and put fresh rubber ones in the uppers as well.
You said the uppers are still in good shape, but keep in mind that regardless of the lack of misuse, they are still 30 year old bushings.
Add that to the fact that when you install poly in the factory arms you are removing a load of compliance, which will all be transferred to the upper arms.
So don't cheap yourself into having to get back under there in a couple of months because the 30 year old bushings crapped out.
 

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Discussion Starter #8
Funny how things come in waves.
Several years ago the factory style rubber replacement bushings were impossible to find.
About 3 years ago they were everywhere, and here we are again with them impossible to find.

My suggestion is to buy the poly bushings and swap them into the lowers, but go ahead and put fresh rubber ones in the uppers as well.
You said the uppers are still in good shape, but keep in mind that regardless of the lack of misuse, they are still 30 year old bushings.
Add that to the fact that when you install poly in the factory arms you are removing a load of compliance, which will all be transferred to the upper arms.
So don't cheap yourself into having to get back under there in a couple of months because the 30 year old bushings crapped out.
Yeah it is funny how things work that way. I replaced the bushings in the diff housing already. And yeah I probably will go ahead and get stock replacement rubber bushings for the upper arms. The car is in storage till spring. Canadian winters get kind of rough lol. Thanks for the advice. Ill repost in the spring after the results.
 

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I did the Prothane rear bushings in stock rear arms. Worked fine for me. Later I found a set of nearly new tubular upper/lowers in the wreckers and picked them up. They are on my car now and really didn't notice much if any difference between the poly bushed stock arms to my current ones.

I hear you about the parked for the winter thing.
 

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Discussion Starter #10
I did the Prothane rear bushings in stock rear arms. Worked fine for me. Later I found a set of nearly new tubular upper/lowers in the wreckers and picked them up. They are on my car now and really didn't notice much if any difference between the poly bushed stock arms to my current ones.

I hear you about the parked for the winter thing.
Did you put the poly in the upper arms also? Did you have any bind issues? Thanks for the advice.
 

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Did you put the poly in the upper arms also? Did you have any bind issues? Thanks for the advice.
The question was not pointed at me, but I made the mistake several years ago of going all poly, upper and lower.
After only 3 years, I went back and revisited the uppers based on info I had been exposed to.
Sure enough, the poly upper bushings were trashed.
You should have rubber on both ends of the uppers because of the double duty they perform.
 

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Discussion Starter #12
The question was not pointed at me, but I made the mistake several years ago of going all poly, upper and lower.
After only 3 years, I went back and revisited the uppers based on info I had been exposed to.
Sure enough, the poly upper bushings were trashed.
You should have rubber on both ends of the uppers because of the double duty they perform.
Thanks for the input and I'm thinking thats the way ill go. Leave the uppers as they are and go poly on the lowers.
 

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Here's the thing with poly - no on the uppers. As pointed out, the uppers were designed to perform two functions - axle roll control and axle lateral control. In order to preform these functions the bushings/Arms need to twist and grow in length. The twist/growth occurs primarily through the compliance of the rubber bushings. Poly doesn't permit this to occur meaning bind occurs earlier in the arm's articulation path. Bind result in the wheel rate going to infinity causing immediate loss of traction. Generally, with poly this is a sudden event (snap-oversteer), whereas with rubber it is more gradual to bind allowing the driver to correct.

The lowers perform one primary job - squaring the axle to the front suspension. Here poly or spherical bushings can be used. But these arms still need to articulate smoothly. To accomplish that with poly, the bushings need to be three piece, not one piece such as those typically sold as stock replacements or in less expensive arms.

We understand budget constraints but most of us (myself included) didn't know any better and made mistakes. This forum and others like it allow newbs to learn from experienced posters and hopefully, save you time, resources and disappointment.
 

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To the OP,
If you do go poly, buy a tube of Sill-Glyde synthetic grease from NAPA and liberally lube everything that moves, rubs.
I did so and never have had any creaks or squeaks.
As for the front only....I don't know. You will have to look into it.
 

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Would love to go with MM for everything but its just not in the budget right now. Not really looking for a benefit from the poly. I just need the oval bushings replaced in the lower arms. And cant find replacements anywhere. I can get the full poly kit for the rear arms for$50.
If you can't afford the cheap MM arms (under $200), then I guess it is what it is then. If you look through Moog's catalog, or even Rock Auto, you probably will find replacement rubber bushings, and for less than the poly. Keep in mind too, sometimes the polys require you to reuse the shells. Taking out the rubber, and leaving the shells behind, is not really as easy as just pressing the whole thing out. But, the other coin to this is, you need to make sure the rubber bushings are from a good brand. Chinese rubber parts are really bad. At least steel will be steel if screwed up in the forge. Rubber though isn't rubber if you screw up the vulcanization. Poly by its nature is more tolerant of bad manufacturing.

If you truly want to upgrade, you need to find something w/ a three piece design minimum. If you just want to replace worn bits, get rubber from a good brand (Moog, for example).
 

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Did you put the poly in the upper arms also? Did you have any bind issues? Thanks for the advice.
I did full poly all around, uppers and lowers. No bind that I noticed, but I have seen no track use either. I did have to adjust the metal sleeves on the axle housing for the uppers (due to the shoulder on the poly bushing), otherwise my uppers would not install (too much side deflection required to get them on).

If I disconnect my shocks I can get full droop by gravity.
 

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I did full poly all around, uppers and lowers. No bind that I noticed, but I have seen no track use either.
I guess I should clarify my above statements. If the car is a drag car pretty much dedicated to those events, then the corresponding pieces (e.g., big-'n-littles, 90/50 shocks, light front springs, removed front stay bar, etc.) together with running polys on all rear arms may not hinder handling all that much since the car isn't designed that way.

But most guys' cars do double if not triple duty, one of which is "spirited" street driving. Doing corners at an aggressive speed will cause an all poly rear suspension to bind unexpectedly, generally at the wrong time causing a spin (oversteer). Oversteer is very hard to correct even for experienced drivers. That is why most OEMs build in understeer so the driver has more control in a slide. Moreover, if "track" means open track/HPDE events or autocross, then poly is the wrong solution except where I've mentioned. In those events we want the rear suspension to be as compliant as possible and not bind - hence the reason for T/As, PHBs, 3-links, even IRS systems.

I think one of the larger misconceptions is that some of the internet solutions preach "upgrade" where in many situations that is far from the case.
 

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I've been looking around...
The Moog part number for the lower rear bushings is K8812.
I found some at Carid.com


Order Details
MOOG® K8812 - Rear Lower Control Arm Bushings
SKU: 537140742​

Ford Aerostar Extended Passenger Van / Mini Cargo Van / Mini Passenger Van 1990-1994, Rear Lower Control Arm Bushings (K8812) by MOOG®. Replace your worn or damaged bushings with stronger and...​
Fits Following Model(s):
• Extended Passenger Van / Mini Cargo Van / Mini Passenger Van​
Price:​
$19.34​
Qty:​
1​
Delivery:​
$11.55​
Total:​
$30.89​


Subtotal:​
$19.34​
Shipping:​
$11.55​
Tax:​
$2.55​
Total:​
$33.44​
 
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