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Discussion Starter #1
Does anyone know if there is an aftermarket Poly bushing for the main IRS busings?

The bushings that I am talking about are the ones that go inbetween the IRS and the frame at the 4 corners where the IRS bolts to the body.

Mine are shot, and while I have the IRS down for the strengthening, blasting, and painting, I am replacing all bushings in the rear, and replacing all I can with Poly.

Please let me know, otherwise I am going to have to drop about $200 for the bushings from Ford.
 

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Discussion Starter #4
I appreciate the links, and suggestions guys, but those are NOT the bushings that I am talking about.

If you look at your IRS, right behind the doors where the IRS attaches to the body/frame, there are 4 bolts that ultimately hold the IRS to the body/frame. these bushings are like about 3-4 inches in diameter. NOT the ones for the Pumpkin (8.8 diff). These bushings actually buffer between the IRS and the body at the extreme corners of the IRS.

Are there any aftermarket bushings for these?
 

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joshbea6 said:
I appreciate the links, and suggestions guys, but those are NOT the bushings that I am talking about.

If you look at your IRS, right behind the doors where the IRS attaches to the body/frame, there are 4 bolts that ultimately hold the IRS to the body/frame. these bushings are like about 3-4 inches in diameter. NOT the ones for the Pumpkin (8.8 diff). These bushings actually buffer between the IRS and the body at the extreme corners of the IRS.

Are there any aftermarket bushings for these?

Those are the rear body mounts. Really no need for those to be poly that I can see.

-Miller
 

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miller1995 said:



Those are the rear body mounts. Really no need for those to be poly that I can see.

-Miller
Possible help for wheel hop.

I don't believe anyone makes any. You could get some custom made or get AL mounts made....


Russell
 

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Discussion Starter #8
Wouldn't AL mounts be too rigid for the frame? I thought that there needed to be some flex at those points, hence the rubber bushings?
 

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There is a guy I have talked to that worked with the Boundurant driving school, and he said that was a very worth while modification for them. It was something that Bob himself came up with. I'm not sure if you are familiar with the Boundurant driving school but you can find stuff on google I'm sure. The mounts need to be stiff. The pieces of rubber that need to stay (like Duffy Floyd on SCCOA talks about) are the LCA, UCA, and knuckle bushings. If the chassis mounts are deflecting then it already puts the geometry (this is under hard load whether it be drag racing or cornering) out of wack and then the bushings for the arms deflect and well...I think you can see the problem. The guy did mention that it increased the NVH, but still said that if you were semi-serious and knew someone that would make them it was a good idea.

Russell
 

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96bird said:
The pieces of rubber that need to stay (like Duffy Floyd on SCCOA talks about) are the LCA, UCA, and knuckle bushings.
Just rubber, or is Poly an option? (or will Poly be too stiff? I should be browsing SCCoA more often I guess :) )


As far as those IRS main bushings. I've read 4CamBird's commentary and he believed they would be a little complicated to machine from Aluminum. It's apparently not a simple flat bushing? I haven't taken time or had the need to look at mine real close.


On the issues of stiffness from Aluminum. Yes it may improve things, but would it cause (or provoke more) cracking issues? I've read enough of the problems on cracking of the firewall and other areas (rear seat) around the MN12. I know one guy who's reccomended to even stay away from Poly bushings as it'll tighten things up too much, not allow the chassis to move like it was designed to, and provoke cracking.


I'll expect pictures and commentary after you're done with this joshbea6. :cool:

-jw
 

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The poly doesn't have the "give" that the IRS was designed with, so rubber is what you would want to use on the regular bushings. The other thing with poly bushings is that in places where the supension would be moving in two directions (like the rear knuckle bushings) the poly will bind up. The reason for this is that the poly pushes the grease out after a week or so of putting it back together or the first time that you drive through the rain it can wash the grease out. This is heard in the form of squeeks. Once you hear the squeeks you have already needed the grease for a while.

I'm not sure that the bushings are easy to make, but....when has anything been real easy on these cars. I'll probably look at going with the AL when I do my subframe buildup, but I will probably just go back with the rubber for simplicity. Having the mounts stiff should not affect the motion of the IRS, so there shouldn't be any cracking from putting AL in the chassis mounts.

94Tbird UMWTC Prez,

Search for Ultimate suspension on SCCOA. The thread is called Ultimate suspension and chassis upgrades. I believe Duffy talks about bushings on the 2nd page. He talks about it in depth in a few other threads as well but that is the only one I remember off hand.

Russell
 

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Discussion Starter #13
There is a discussion about just these bushings on SCCOA, they are the rear subframe isolator bushings.

Here is the link:
Subframe Isolator Bushings

I am still waiting on the body shop to get the car into the shop, hopefully early next week, it keeps getting pushed back. I'm going to try to get some loaded measurements, and also get the unloaded measurements as well.

I just want to know why these bushing are still in rubber, and not Poly. I have heard that you can also do them in Aluminum, but I am worried about the unibody stresses if we hard mount the rear subframe. I don't want the $1200 I put into a new floorpan to go to *$%& because I was stupid.
 

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joshbea6 said:
I just want to know why these bushing are still in rubber, and not Poly. I have heard that you can also do them in Aluminum, but I am worried about the unibody stresses if we hard mount the rear subframe. I don't want the $1200 I put into a new floorpan to go to *$%& because I was stupid.
Very understandable. I have chassis braces and will have a 6-pt. rollbar probably before I do the subframe buildup, so I won't be worrried about stress fractures. The added stiffness of the chassis will aid in keeping from having stress fractures. It will take some of the strain away from the weaker body panels that were flexing with the subframe before.

Russell
 

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Here is a guy that sells some in AL for anyone reading this that is interested. click


Russell
 
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