I am contemplating doing a cobra IRS swap, preferably a trade with someone local, I am in Oregon if anyone is interested. Current axle is a 2000 gt with 3.73 gears and very very tight limited slip. Anyway my car has been lowered with eibach springs and would look weird if I used stock cobra springs since it would ride high in the rear. Would my GT eibach springs bolt in with the IRs swap, therefor maintaining the lowered ride height? I know the spring rates are different because of the suspension geometry. Would there be an easy way for me to lower the cobra springs to match the front without using a torch, ie those interesting coil spring clamps, can't believe I even suggested those but would that work or would I be best off just using my gt eibach springs?

 

Good luck finding anyone in Oregon.
So far that I know of it's just me and another girl who doesn't come on the forum anymore. haha

Your making me want a Termi so bad right now. Post some pictures of your vechile, I want to see .

 

HEres some pics and also of my previous 5.4 supercharged crown vic.
http://s412.photobucket.com/albums/pp202/bjorkmae/

 

Sweet car. Where you located?

 

Moved to suspension talk.

 

No and no.

Your GT springs won't work, and without cutting the coils you're not going to get it and lower.

Just grab up some rear springs off of SVTP. Plenty of guys sell them separately when the swap to a SRA.

 

How much is a good price to pay for the rear IRS assembly? I was thinking $400 would be a good deal.

 

I'm not so sure that you had a vortech strapped to a 5.4 in a crown vic with stock hood. I also havent seen a vortech hooked up to a 5.4 like that either.


No, you cant use SRA springs with IRS.

You could proably buy a used set of springs off of forums pretty easily or use EBAY. Your best bet is to find someone with a 03-04 IRS that wants to swap to SRA and already has a lowered springs and a cat back you can trade with as well.


If your willing to drive to Florida and spend about 1000 bucks I have a buddy with a torsen differential, 4.30 gears, stage 2 half shafts, bracing and bushing upgrade 03-04 Cobra IRS for sale. Thats a uber expensive rear end that is practically un-breakable. Oh he has MM coil-overs on it as well.


Edit: Okay. I looked at your pics of the 5.4 crown vic and seen some of the differences in the bracket. Do you have any other pictures of the bracket being test fitted to the timing cover?

I lent out my 96-99 mustang vortech bracket to see if they can use it as a template toward making a better product for people that want to set up a centrifugal supercharger to their 5.4 liter swapped mustangs.

 

Considering the large amount of time I spent working on the crown vic I think I would know what was in it since I put it there. Check out the videos with my pictures you can see and here the supercharger running. Also look at the pictures of the 4.6 to 5.4 swap. That should make it pretty obvious.

 

I corrected myself with my "Edit" above. I acknowledged that your crown vic had the 5.4 with the vortech hooked up and that you had to backyard engineer a new mounting hole. Then like a light bulb I said to myself ahhh that's how he made it work.

That's when I went on my ramble to see if you had any more pics of the vortech bracket being fitted to the 5.4 timing cover. Only because I believe that a 96-99 mustang vortech bracket will affix itself to a 5.4 with minimal modification but it seems risky to not use a reinforced mounting hole.

Edit: just to be clear. The edit in my post above was there before you made your rebuttal to correct me. But I had already corrected my mistake.

 

I know you did the edit, because it was there when I read the post. I just figured you hadn't seen the videos yet or the swap pics and thought you might want to take a look since you seemed interested thats why I pointed out the video. Anyway its all good no offense taken.

 

No worries....sometimes people are sensitive on forums. Didn't want to come off as a dick.

Yes I am interested. Once my car blows its 4.6 ill toss in a 5.4 and still try to use my vortech with it. Didn't think it would be possible but now I know there is a way to make it work.

 

Yes it is possible but I had a difficult time getting the belt tensioner and belt length to work out correct so that the belt didn't slip on the supercharger. Unfortunately its been over a year since I had the car and I can't remember exectly how I did it. The front cover on my 5.4 was from a van and if I remember correctly they seam to use different front covers on the 5.4 depending on if its in a truck or van. Not saying you should specifically buy a van front cover as a truck one might be easier to make work or about the same amount of work. In the end I ended up being creative with the top idler pulley that comes with the supercharger to ensure 50% plus supercharger pulley to belt contact and that seamed to solve the slipping issues. Also make sure that the alignment between the supercharger pulley and the belt are perfect otherwise it will just make heat and ruin the belt. One of the biggest issues was the fact that the 5.4 has completely different belt tentioner mounting. I also used the 6 rib pulleys from my crown vic and not the 8 rib on the 5.4 so that my assesories would work.

 

I would advise against the IRS. You can get better handling and none of the fragility out of a tq arm package with either a watts or a PHB.

Call up maximum motorsports.

I've broken more IRS's than most people will ever touch. If you're not wanting to drop 1500 bucks modding the IRS it'll always be just a fragile POS made for those that are afraid of a well handling car.

IRS spring rates are vastly different from GT rates. Use ONLY correct IRS springs. You're looking for about 600-650lbs/in in the rear and about 600 up front with conventional springs and an IRS for a car lowered about an inch and a half (normal).

 

Wow $1500 just modding the IRS? Plus purchase? I thought all I needed was a bushing kit to avoid wheel hop with the mods I have listed will the IRS still just break, I have less power than a cobra would have stock. Ok I have heard that the irs will always corner better and have a smoother ride, our roads here in Oregon seam to be deteriating and its getting to my back.

 

making it not wheelhop is directly contra to making it comfy. I would seriously consider putting a call in to MM.

A proper bushing kit is about a grand last time I checked. Poly won't do jack for the thing. You need delrin+aluminum in almost all the bushed locations. Apart from the bushings you'll want a diff brace and some beefed up axles. The thing will still break if you whip it on the street. No way around that. If you want it not to break then you'll want a billet rear cover and an iron center section and all the other mods and a diff cooler if you want to get all brutal on it.

The IRS corners for **** upside a properly set up 3 link but a IRS is easier to drive overall (it just won't keep up at the end of the day). What it will do is ride smoother. At the limit it randomly decides which way it wants to go.

If ride is your concern then take the advice of someone that got an IRS because of his bad back in the first damned place and found out it's worth no more than 2 squirts of cold ****. 3 link for handling, coil over conversion and a smart spring choice (4 wheel) for comfort.