IRS Swap, I Searched But Have More Questions...

[Blinkstang]

Alright I did a search on this and found a lot of good info. Just had a few more questions. Oh and this is for my 2002 GT, swapping out the solid for IRS...

Now is there any major differences between the 99-01' Cobra IRS and the 03-04? From one of the threads I read, someone said something about the 03-04' IRS having fixed some wheel hop issues over the previous Cobras. On top of that I would assume the 03-04' to have better shocks, coming stock with the Bilsteins, what does the 99-01' come with?? But they do have the same rear brakes right?

Also, if I was directly swapping with an 03-04, would the only other thing I need to get be that new driveshaft yoke to hook up to my 3650 tranny?? And does anyone have a link on where to find that?

Everything else would be a direct swap right, like the parking brake cable, etc... or would I need to pick up some other small things, or maybe some things that would be a good idea to get while Im back there already (like SS brake lines for the rear someone mentioned in an older thread)?

Thanks for the info guys! My car is a daily driver and doesnt see the track, just the craptastic streets of Chicago, so this is for ride comfort.

 

[Blinkstang]

Bump...

 

[Stang2003GT]

Where do you find the IRS. I am also interested in this swap.

 

[Blinkstang]

I found a local guy who wants to do the swap, thats your best bet.

 

[BennyBlown2v]

Ok...

The 99-01's didn't have the same diff cross member brace, the shocks weren't as good, the halfshafts (axles) were of a lower spline count, and the diffs weren't as good. The 03-04's diff's have carbon fiber clutch packs, and also the halfshafts are 31 spline, and much more durable.

My suggestions...

Get coilovers right off the bat. MM has a great kit that you can use with the bilsteins that come with 03/04 cobras with just the addition of a bushing kit and the shock bodies have to be milled. Next, get new subframe and diff bushings. I went with urethane to avoid some of the possible NVH that is associated with aluminum diff bushings. Control arm bushings may be something to consider, but they are pricey, and so far I haven't had any hop (except in the rain when also giving it WAY to much gas ) with my setup.

Oh yeah, and SS brake lines would be nice, but they really aren't needed. The stock GT lines (and calipers!) WILL even work! I just bent mine so they fit over the upper arms, and with the coilovers there is no interference from where the in-arm coil springs would be.

Checkout the link in my sig (picture) for pictures of my setup.

 

[tomustang]

Ok...

The 99-01's didn't have the same diff cross member brace, the shocks weren't as good, the halfshafts (axles) were of a lower spline count, and the diffs weren't as good. The 03-04's diff's have carbon fiber clutch packs, and also the halfshafts are 31 spline, and much more durable.

stiffer spring rates aswell

 

[BennyBlown2v]

TRUE!

Also, Blink, if you end up getting a 99-01 setup and want some stiffer rear springs, I have a set of 03/04 coupe springs you can have for shipping + $10 for the box/driving to the store lol.

 

[Blinkstang]

Ok...

The 99-01's didn't have the same diff cross member brace, the shocks weren't as good, the halfshafts (axles) were of a lower spline count, and the diffs weren't as good. The 03-04's diff's have carbon fiber clutch packs, and also the halfshafts are 31 spline, and much more durable.

My suggestions...

Get coilovers right off the bat. MM has a great kit that you can use with the bilsteins that come with 03/04 cobras with just the addition of a bushing kit and the shock bodies have to be milled. Next, get new subframe and diff bushings. I went with urethane to avoid some of the possible NVH that is associated with aluminum diff bushings. Control arm bushings may be something to consider, but they are pricey, and so far I haven't had any hop (except in the rain when also giving it WAY to much gas ) with my setup.

Oh yeah, and SS brake lines would be nice, but they really aren't needed. The stock GT lines (and calipers!) WILL even work! I just bent mine so they fit over the upper arms, and with the coilovers there is no interference from where the in-arm coil springs would be.

Checkout the link in my sig (picture) for pictures of my setup.

Thanks for the info! I was looking into the upgraded bushings for sure, as I read they reduce wheel hop quite a bit. And the Bilstein coilover idea sounds good as well, did MM charge you to send in the Bilsteins to get milled?? Or did you have it done elsewhere?

Also, did you have any vibration issue? I heard some get this because you have to get the driveshaft in laser straight to not incur any problems. And apart from being a direct swap, was the only thing you had to pickup to make it work that u-joint adapter for the yoke for your tranny versus the T-56?

Oh and for springs, I have H&R Sports now, so Im gonna pick up a set of Cobra H&R's if I end up doing this. I would have quite the raked look with stockers out back and a 1.6 inch drop up front, haha. But then again I may end up going the coilover route as you mentioned.

Still talking to the guy about the swap as I type, hopefully it goes through!

Thanks.

 

[Blinkstang]

Bump... (for new questions for Benny)

 

[BennyBlown2v]

Thanks for the info! I was looking into the upgraded bushings for sure, as I read they reduce wheel hop quite a bit. And the Bilstein coilover idea sounds good as well, did MM charge you to send in the Bilsteins to get milled?? Or did you have it done elsewhere?

Also, did you have any vibration issue? I heard some get this because you have to get the driveshaft in laser straight to not incur any problems. And apart from being a direct swap, was the only thing you had to pickup to make it work that u-joint adapter for the yoke for your tranny versus the T-56?

Oh and for springs, I have H&R Sports now, so Im gonna pick up a set of Cobra H&R's if I end up doing this. I would have quite the raked look with stockers out back and a 1.6 inch drop up front, haha. But then again I may end up going the coilover route as you mentioned.

Still talking to the guy about the swap as I type, hopefully it goes through!

Thanks.

Wow just saw this on a search, sry for the late reply! lol...

MM doesn't charge for the milling, just the shipping cost to get it there - then they send it back free of charged milled and they even took the eyelet bushings out for me!

I have no vibration from the driveshaft, and just a little driveline noise from the stiffer bushings. Also the stock GT driveshaft is fine, the cobra driveshaft will not work, it's far to short. Yes, you can use a U-joint to adapt the flange on the driveshaft to the centering flange from a cobra... HOWEVER, most people don't include this with a swap, so it might be easier to take the flange off the solid rear with a gear/pulley puller and puting that on the IRS and vice versa (and you need a special ford tool to hold it steady when unbolting it...i just made mine outa some steel stock, on one end I put the GT bolt pattern and on the other the cobra hah).

As of today I'm completely happy with the IRS for the street - not nearly as pleased with its the drag performance (to be expected, but it still sorta sucks losing traction 1-2 + 2-3 + 3-4 shifts on drag radials ) - and this weekend I'll see how it holds up during an autox. I'll let you know if I'm still an IRS fan then