IRS Swapped Cars please post!

chris91

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Okay so I'm hopefully trading off my SRA for a IRS outta a 03 Cobra. Dont know anyone who has done the swap personally so I figured I'd post up on here and get some opinions. Lets hear the good and the bad of the swap. Main reason I want to do this is because I don't drag race my car and have always loved to whip it around some corners. Plus if it makes the ride a little better, than the wifey might actually like taking rides in it again.(Bad car wreck screwed her back and neck up royally.)
 

330CubeGt

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I have done the swap on 2 of my cars... know anything about the swap? Looking for certian info?

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330CubeGt

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My old setup before I went back to SRA for drag racing reasons... Car will cut corners like a beast and ride smoother then any SRA axle mustang
4una6uta.jpg


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chris91

chris91

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I've read quite a few write ups and think I have it down. Any tips or tricks are welcome though! One nice thing about the 99-04 GT is it already has the holes for the brackets so thankfully I dont have to go drilling into my car for it.

And yeah thats what I was looking for. Just peoples opinion on the ride and performance of the IRS. Any idea what I should upgrade first on it? Its a bone stock rear down to even the gears. I was thinking, Brace and Diff Cover first. Then save up some money and go with the FTBR Bushing kit for it. I dont ever plan on having the car over 500 HP so the axles should be good right? Also, it wont see Slicks or Drag Radials so there shouldn't be any harsh launches.
 

Mystic SVT

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If you have the money go ahead and buy a diff brace and FTBR diff mounts (front/rear) at least so you can get those out of the way and help some with wheel hop. Remember to remove anything and everything SRA related; exhaust hangers over axle assy, pinion snubber, springs, quad shock brackets, etc.

As for comfort, it gives a much better ride than the SRA and lets the car take turns a lot better.

As for tips and tricks, when installing the IRS make sure when you are jacking it up to install you do it evenly so you can get the front mounts inside the mounting pocket points. Put the bolts in (buy the correct 14mm from ford or buy grade 8 9/16 nuts/bolts and drill out the guide) and let the IRS hang down a litte from the rear so you can get the springs in. Once you get them in then you can go ahead and jack up the IRS and secure it at the rear mounting points. You might have to persuade it a bit to fully go all the way into the rear brackets. Back to the 14mm bolts (or 9/16 whichever you want to buy), make sure and do this since Ford installed the wrong size bolts in almost all 03-04 cobras so there is some play in the lower mounting points of the IRS. These bigger bolts take up the slack but you have to drill out the part of the mounting area (takes 5 min).
 

RonBurgandy

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I got an 01 irs and before i put it in im gettin the entire ftbr bushing kit and 03 shafts. And braided irs brake lines. I gotta get mine set up good cause it will have to handle some serious power later on when i go turbo. Mine will be for raod track and country roads

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the.greg

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I highly recommend doing the bushings first, but if you dont do the bushings first, be careful of wheel hop. Wheel hop is the number 1 thing that will hurt your halfshafts. A diff cover plus the bushings everyone else already recommended and you will be all set and should have no worries unless you start launching and hooking very regularly (as in drag racing all the time) then you may need to look into some beefier halfshafts.

FYI the 03-04 cobras are stronger than the 99 cobra halfshafts. I believe 31 spline vs 28 spline on the 99 cobras.

Also stock gears for 99-01 are 3.27 vs 3.55 on the 03-04s
 

Mystic SVT

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...then you may need to look into some beefier halfshafts.

No need to go to anything stronger than 03-04 shafts, they are strong enough. Many guys running 9's on stock 03-04 halfshafts, just need to replace all the factory soft bushings with FTBR's kit. People going with level 5's are still breaking them as easy as 03-04 shafts and its because they don't replace the factory bushings. Like you said, wheel hop kills halfshafts, ALL HALFSHAFTS.
 
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chris91

chris91

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Thanks for the info guys. I do believe the 99-04 cars already have the bigger bolts for the front lca mounts. I had 94-98 ones in there before and they had some play to em. So I went to Ford and ordered the right ones. As for diff covers, which one do you guys recommend?
 

Mystic SVT

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^^^nope, IRS uses 14mm and SRA uses 12mm, I installed an '04 IRS into my gf's Mach and had to install 14mm bolts into it too.
 
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chris91

chris91

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Okay good to know. When I go to Ford to order them do I ask for the bolts for a 04 Cobra or what? And these are the bolts where the front of the LCA bolts into the Torque Box correct?
 

ScottyDsntKnow

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Subscribbling. Hey I am wondering for the 94-98 cars how much of a pain is it to drill the mounting holes since they don't have them? Is it as simple as just jacking it into place, pulling the material out of the trunk and just drilling? Good idea to do any sort of bracing plates or battle boxes while the thing is out or does the IRS not need them?
 
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chris91

chris91

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Oh and Mystic, what exhaust you running there man? I was more than likely going to buy another Bassani catback since I love the way mine sounds now. The rear will be coming with an Aluminized Flomaster setup so no polishing for that one. :(
 

twovalveterror

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I had all the bolt numbers laying around somewhere, I'll see if I can find them. I just went with hardware from Lowe's in the end, just measured and bought grade 8 hardware.

I'd recommend getting the button headed rear sub-frame mount bolts from MM, they give you a little bit more room for tire, and won't do as much damage should they still rub.
 
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chris91

chris91

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Ill be running my 18x10's with 275/40/18 on em so I doubt Ill have any problems with the rubbing since the Terminators came stock with 275's.
 

Mystic SVT

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Oh and Mystic, what exhaust you running there man? I was more than likely going to buy another Bassani catback since I love the way mine sounds now. The rear will be coming with an Aluminized Flomaster setup so no polishing for that one. :(

Bassani mufflers with SLP piping and exhaust tips.
 

95riosnake

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Regarding the larger 14mm bolts, I'm not sure if you have to drill out the LCA holes on new edges or not but if you do have to, make sure you do it before you're hoisting that big heavy bastard into place. I finally had that damn thing up in the car and went to slide the front two bolts in, then immediately realized I forgot to enlarge the holes. I could have punched a baby. Getting that IRS in place w/o messing up the powder coating was stressful to say the least, then I had to do it twice lol.

One other tip I got from FTBR is to use a porta-power or threaded rod/washers/buts to widen the lower torque boxes where you'll bolt the front two cradle points in. It'll help it slide up in place easier. I used a porta power to widen mine.
 

Magic

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Subscribbling. Hey I am wondering for the 94-98 cars how much of a pain is it to drill the mounting holes since they don't have them? Is it as simple as just jacking it into place, pulling the material out of the trunk and just drilling? Good idea to do any sort of bracing plates or battle boxes while the thing is out or does the IRS not need them?

I didnt drill holes for the vertical bolts on that rear bracket. I bolted the bracket on (side bolts) and welded the bottom half to the frame.
You can go either. Drill holes, or weld the bracket. OR both!
 

Magic

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