'01 vs '03 IRS

[Bullitt1448]

I have an opportunity to buy a complete IRS out of an '01 Cobra, what is the difference between the '01 and the '03? Keep in mind that this would go into an '01 Bullitt with the '03 engine and T56.

Thanks for your help

 

[01yellercobra]

-The 01 doesn't have the pinion brace tabs under the diff. Easily added if you can fabricate or you can track one down online I'm sure.
-The 03/04 has stiffer durometer bushings. But that shouldn't matter as you should be upgrading anyway.
- Both have 31 spline inner CV joints. However the 01 half shafts are smaller. You can swap in a set of 03/04 half shafts easily. Or upgrade to aftermarket.
-The 03/04 has carbon fiber diff clutches. I'm sure it's an upgrade, but I never noticed a difference when swapping between them in my 01.
-01 has 3.27 gears. 03/04 has 3.55.
-The 03/04 has a larger diameter pinion flange. The 01 is the same size as the other 8.8's.


I think that hits them all. My mostly stock 01 IRS lived behind my big bore stroker/F1A, T-56 combo for a long time. I didn't beat on it all the time though. I did grenade one half shaft getting on the freeway. I shifted into 3rd coming off a sweeping on ramp and the outside shaft said no more. That was the only issue I ever had with it.

 

[Bullitt1448]

Thanks for the info, just the kind of information I was hoping for. I have the chance to buy an 01 IRS for fairly cheap but I know it’s going to take some work to get it up to snuff. It’s a sight unseen buy and that is why I am dragging my feet a little

 

[01yellercobra]

Depending on how cheap, I wouldn't let the fact that it's an 01 deter you. It doesn't sound like you're the type to beat the crap out of your car. I consider the bushings a moot point as they should be upgraded whether it's an 01 or 03/04. Especially since it's out. Plus you'll be able to powder coat everything to be as nice as the rest of the car. At a minimum I would do the diff and cradle bushings. Those made a noticeable difference in my 01. Oh, and the FRPP diff cover.

FTBR has the under pinion brace for about $150. But like I said, if you can weld you can add your own to the 01 brace. That's really all Ford did.

I'll say the gearing is a personal preference. I kept the 3.27's forever. The torque of the big bore helped get the car moving. I'm sure it would be the same with the PD blower. I eventually went 3.90's because it was a free swap with a friend. It was fun for a bit, but if I had kept that car I would have swapped to 3.73's or 3.55's to quiet things down on the freeway a little.

When I grenaded the half shaft I was well over 600hp and on drag radials. Not running drag radials will help the stockers live longer. Or you can keep an eye out for a set of stock 03/04 shafts from someone that upgraded. The G Forces are nice pieces though. I'm glad I went with them.

And let's not forget the sexy IRS tail pipes that complete the look.

 

[Bullitt1448]

Depending on how cheap, I wouldn't let the fact that it's an 01 deter you. It doesn't sound like you're the type to beat the crap out of your car. I consider the bushings a moot point as they should be upgraded whether it's an 01 or 03/04. Especially since it's out. Plus you'll be able to powder coat everything to be as nice as the rest of the car. At a minimum I would do the diff and cradle bushings. Those made a noticeable difference in my 01. Oh, and the FRPP diff cover.

FTBR has the under pinion brace for about $150. But like I said, if you can weld you can add your own to the 01 brace. That's really all Ford did.

I'll say the gearing is a personal preference. I kept the 3.27's forever. The torque of the big bore helped get the car moving. I'm sure it would be the same with the PD blower. I eventually went 3.90's because it was a free swap with a friend. It was fun for a bit, but if I had kept that car I would have swapped to 3.73's or 3.55's to quiet things down on the freeway a little.

When I grenaded the half shaft I was well over 600hp and on drag radials. Not running drag radials will help the stockers live longer. Or you can keep and eye out for a set of stock 03/04 shafts from someone that upgraded. The G Forces are nice pieces though. I'm glad I went with them.

And let's not forget the sexy IRS tail pipes that complete the look.

Thanks for the info. I expect to do all the bushungs and powdwer coat evwerything I under there while it's apart. I will likely swap to 3,73's that's what I have in my SRA right now.

 

[Blkkbgt]

Thanks for the info, just the kind of information I was hoping for. I have the chance to buy an 01 IRS for fairly cheap but I know it’s going to take some work to get it up to snuff. It’s a sight unseen buy and that is why I am dragging my feet a little

I'd ask yourself why you want it before committing to the swap.

I'd compare the price of the IRS and all the parts needed to fix its problems against further building your SRA. Don't forget the price of a new cat back too.

Don't get me wrong here, I love mine and wouldn't swap back for anything but it was no joke expensive. Mine ran me close to 3k when it was all said and done.

Now I'll admit I could have done it cheaper but I went all in and replaced all my bushings with the FTBR kit. The diff clutches were toast so I had the whole diff rebuilt and swapped the pinion flange. That alone was another $400. New exhaust, new set of H&R race springs, new struts/shocks.

Worth it in the end? Hell yes! But again not cheap.

I will also say if you want the car to ride better go for it. It's honestly an unsung benefit of the IRS most gloss over. My wife almost immediately commented the smoothness when she road with me the first time after the swap.

If you go ahead with the swap feel free to hit me up with any questions you have.