IRS swap questions.

[GO2REDLINE]

Might do a swap to 03 Cobras IRS. Buddy wants an 8.8 to drag with and i like IRS soo...

Aside from different gears, shocks, and the FR500 brace, is the 03 COBRA IRS any different from the 01 COBRA's?

After doing the swap would i just order suspension kits for an 01 Cobra? Or how would that work..

[Azure]

The 03 IRS also has:
Stronger halfshafts
Stronger cast upper control arms
harder bushings

[Silverstangs]

Originally Posted by GO2REDLINE

Might do a swap to 03 Cobras IRS. Buddy wants an 8.8 to drag with and i like IRS soo...

Aside from different gears, shocks, and the FR500 brace, is the 03 COBRA IRS any different from the 01 COBRA's?

After doing the swap would i just order suspension kits for an 01 Cobra? Or how would that work..

I've done many many IRS swaps, I'm gonna give you a hint that most people don't even know about... You will need to swap the pinon flange between both cars BECAUSE, the 03~04 Cobra's have a bigger pinion flange bolted into the IRS pumpkin. The GT's/ V6's Mach 1's, Bullits and 99/01 Cobra's all have the same size pinion flange.

And I learned that the hard way being one of the first in my group to do 03/04 Cobra IRS swaps...


You will need to swap the parking brake cables with the cobra ones, because the cobra's use a longer parking brake cable. You will also need to swap the rear shocks and the ABS sensor cables. Other than that, everything else is cake. It takes me about 4~6 hours by myself to do a swap between two cars, depending on how tired I am enjoying a few beers while working.

The shocks on the 03~04 Cobra's have short little extension between the shock body and the bolt eye because the normal shock body would rub against the lower control arm.

If you are going to do the swap, I would reccomend that you spend the money for the IRS Subframe Bushings, it will help button down the IRS.

You want both cars to be up on jack stands, get them as high up as possible because the IRS is kind of bulky, and hard to slide under the cars because the fuel tank is right there in the way if the car is not up high enough. I usually also use 3 floor jacks for the irs, makes lifting it up easy.

Get a couple of metal coat hanger to hang the calipers while your doing the swap. Another tip, there is a brackets on the IRS that bolts to the body frame, If you seperate that from the main IRS carrier, it and bolt that onto the car first, it will make the swap much easier.






Make absolutely sure that you want to do the swap. Not everyone that I have done the swap has enjoyed it. Mostly because they found out that they prefer to do alot of light to light action and hit the 1/4mile track. The IRS is really meant for corner carving, and is definately not meant to go down a drag strip. My brother made that mistake, and I just helped him go back to a live axle. Lucky for him, I was able to hook him up.

I personally love the IRS, and I'll won't go back to the live axle. I love the control and the over all handling that I got with it. I also liked the fact that the IRS made the car feel much more predictible in corners, and I didn't have the rear end breaking loose at every bump. To get a live axle to handle as well, as a IRS, your going to need a Torque Arm and Panhard bar or Watts link.

The 8.8 inch is also a lot cheaper, and easier to upgrade or maintain. A fully built 8.8 inch rear end and suspension is about 1/3rd less in the price of a fully built IRS. Something else to consider is that a stock 8.8 inch rear end and suspension is 93#lbs lighter than a stock 99/01 IRS and about 111#lbs lighter than a 03/04 irs.

[Azure]

I forgot about the pinion flange.

I was able to use the stock Mach 1 parking brake cables. This may be dependent on the car, who knows? I also had to bend the stock hydraulic brake lines to the calipers just a tad to keep them from rubbing.

You will need to remove rear seat to get at the ABS sensor cables. They aren't hard, just do them first while your still clean.

[Silverstangs]

Originally Posted by Azure

I forgot about the pinion flange.

I was able to use the stock Mach 1 parking brake cables. This may be dependent on the car, who knows? I also had to bend the stock hydraulic brake lines to the calipers just a tad to keep them from rubbing.

You will need to remove rear seat to get at the ABS sensor cables. They aren't hard, just do them first while your still clean.

The Mach 1 cables are the same as the GT's but some people have been able to use them, with very little slack, so they get stretched. I have to replace my wife's cables, they finally broke, but I've been too darn lazy to fix it.

EVERYBODY forgets about that pinion flange.

[GO2REDLINE]

Much thanks.... let you guys know whats up.

[Devery]

Do you have a pic of the pinion flange you are referring to???

[Azure]

It's the part the driveshaft bolts to on the front of the diff. It's held on by a 1 1/6" nut.

I don't have a picture for you, sorry.

[G]

Exhaust (CB) will also have to swap. You probably knew this but didn't see it mentioned. My son has swapped his 02 gt rear for a 03 IRS and it worked fine.

[jeffsvt]

You can get an idea of the pinion flange in this picture . It's the round piece the drive shaft mounts to .



I did the IRS to solid swap in my Cobra . I drag race my car a good bit and it was what I needed . Plus with back to back weekends snapping halfshafts that helped my decision .

[DTMach1]

holy crap that looks heavy

[jeffsvt]

Yes it is quite heavy ! Here is a better picture to get an idea of the mess they call an Independent rear suspension . I've heard that the total weight of the IRS is 425lbs and after pulling one I might agree .

[Devery]

Goodness...thanks for the pics. I'll stick with the good old solid axle. What a mess!

[Silverstangs]

Originally Posted by jeffsvt

Yes it is quite heavy ! Here is a better picture to get an idea of the mess they call an Independent rear suspension . I've heard that the total weight of the IRS is 425lbs and after pulling one I might agree .

There is no way it's 425lbs, or I'm much stronger than I thought..and my scales are messed up.

the 99 IRS was exactly 79.6lbs heavier than the 8.8inch rear end from a 2001 GT. I personally weighed them both. Now what I did not do is weight the 8.8inch with the control arms or springs, and both was with rotors but without calipers.

[Silverstangs]

I also didn't weight the springs for the IRS. I'll the images of the scale when I weighed them both. I know it's a 79.6lbs because the girl that was pulling wrenches was commenting on 9.6 and saying she likes it 69 instead......

[Silverstangs]

Originally Posted by Devery

Goodness...thanks for the pics. I'll stick with the good old solid axle. What a mess!

Well the IRS is a 125#lbs reduction in unsprung suspension weight.

[Azure]

I would say the unsprung weight of the IRS is much less the solid rear. Unless I'm looking at this wrong, everything on the solid except maybe the upper control arms are unsprund weight.
On the IRS it would seem the lower control arms and the brake / hub assembly are unsprung and maybe the halfshafts to an extent.

[Devery]

I don't even see how that whole contraption could fit under a Mustang! I'll stay old school...give me a Ford 9 inch up against IRS anyday down the strip.

[Silverstangs]

Originally Posted by Devery

I don't even see how that whole contraption could fit under a Mustang! I'll stay old school...give me a Ford 9 inch up against IRS anyday down the strip.

Yes the 9 inch is definately the way to go if your in to 1/4 mile racing. But some of use perfect a road course instead, and for that, I'll take the IRS anyday.

[Charles236]

Thanks for the pictures and information. I have been considering an IRS swap for a while, and if I find one that I can afford, I probably will change over.

[Silverstangs]

Originally Posted by Charles236

Thanks for the pictures and information. I have been considering an IRS swap for a while, and if I find one that I can afford, I probably will change over.

If your here in Norcal, I can probally hook you up with a straight swap. I think I have another cobra owner looking to go to a live axle.......

[Charles236]

Greenville, South Carolina, but if someone around here was intrested, I could swap. I am a former master auto technician, so the tools and know how are no problem. I worked in a dealership for years, but it was a Chrysler dealership, hence the questions about the nuts and bolts of this project.

[Silverstangs]

Originally Posted by Charles236

Greenville, South Carolina, but if someone around here was intrested, I could swap. I am a former master auto technician, so the tools and know how are no problem. I worked in a dealership for years, but it was a Chrysler dealership, hence the questions about the nuts and bolts of this project.

**** that's definately the other side of the country..............

I should be putting in another IRS in a Fox body soon..... I can't wait too do that. That's gonna push the wheels right flush with the body.

[Devery]

Originally Posted by Silverstangs

Yes the 9 inch is definately the way to go if your in to 1/4 mile racing. But some of use perfect a road course instead, and for that, I'll take the IRS anyday.

NASCAR runs road courses without IRS. I wonder if the rules would allow, would they switch?
:OFFTOPIC:

[Silverstangs]

Originally Posted by Devery

NASCAR runs road courses without IRS. I wonder if the rules would allow, would they switch?
:OFFTOPIC:

Having NASCAR run anything that was not made more than 30 years ago would be like Mr T. wearing a pink dress......... No NASCAR won't change, and they will continue to use a purpose built chassis, driveline and suspension. NASCAR does not adopt new technologies without something really traggic occuring. Afterall, a couple of good drivers should be alive today if they had adopted some of the safety equipment from the get go.

You wonder if the rules would allow a IRS would they switch.... That's pretty obvious, and it's the same reason why they are still using old engine's that have not been in the production line in years. Hell when is the last time you seen a PUSHROD V8 Ford block in a production car..... Is NASCAR gonna change? Nope. Why? They are stuck in the past with their old bias and ways and can not accept change....... just like some people.