03 Cobra IRS swap and weak points

I was looking into this as well. From my research I determined that even with a even swap (no cash changing hands.. just parts) upgradeing the axles (and they're no where near as cheap as 31 spline solid axles) would cost a hell of a lot more than simply beefing up the stock rear end with a Eaton Diff and 31 spline axles. Just remember, theres a reason all the cobra guys want to unload em for our axles.

Mine is in the shop right now for a new driveshaft and diff cover. I was noticing that the rear was clunking during slow speed around town driving. I get under the car and notice that the cover gasket is falling out of the housing with diff fluid all over my rear exhaust. I also notice some play in the driveshaft. So it's at the dealer right now getting it straightened out. I have to say I miss my old GT's solid axle

I get wheel hop really bad in 1 & 2. I'm new to the IRS, its nice driving around corners but I can see problems racing with the wheel hop.

CTGrey02 said:

I was looking into this as well. From my research I determined that even with a even swap (no cash changing hands.. just parts) upgradeing the axles (and they're no where near as cheap as 31 spline solid axles) would cost a hell of a lot more than simply beefing up the stock rear end with a Eaton Diff and 31 spline axles. Just remember, theres a reason all the cobra guys want to unload em for our axles.

Click to expand...

This is only partly true. I think the main reason the Drag Guys want to unload the IRS is because its a lot heavier and more expensive to fix if they do break something.

The IRS swap is something people will do who do not want to drag race alot...

You're not going to snap any half-shafts with less than 400hp if you do the proper mods to prevent wheel hop.

5, 600hp.... probably. 4... no.

Remember... you can break a stock live axle just as easily... Launch it at 6k with some slicks and see what happens.

The 03 IRS also benefits from a stronger differential and the 31spline setup. All else being equal (i.e. a good driver on a good day...) I think the IRS might actually improve a cars launches in a street situation.

5111, The Bullitt was designed to be a Mustang that HANDLED. Make it so.

Bullitt 2496 said:

This is only partly true. I think the main reason the Drag Guys want to unload the IRS is because its a lot heavier and more expensive to fix if they do break something.

The IRS swap is something people will do who do not want to drag race alot...

You're not going to snap any half-shafts with less than 400hp if you do the proper mods to prevent wheel hop.

5, 600hp.... probably. 4... no.

Remember... you can break a stock live axle just as easily... Launch it at 6k with some slicks and see what happens.

The 03 IRS also benefits from a stronger differential and the 31spline setup. All else being equal (i.e. a good driver on a good day...) I think the IRS might actually improve a cars launches in a street situation.

5111, The Bullitt was designed to be a Mustang that HANDLED. Make it so.

Click to expand...

Not really going to argue that. It's just more cost effective to build up the solid axle to me, and I dont plan on staying at 400 HP. I still wanna see how yours rides now that it's done.

... But if you do go over 400hp, you might have wheel hop issues. But that can be helped by getting adjustable shocks and stickier tires.

5111 said:

I have been hearing some bad things about the 03 Cobra IRS in comparison to the solid axle. People have been having trouble with the half-shafts handling that kind of power.

What concerns should I have with a switch? What would need to be upgraded?

I might have someone that wants to do a swap so I want to look into as much as possible.

Click to expand...

If you are into drag racing, then IRS is not the best setup to have. Cobra owners, who drag race, don't like it because it wheel hops and it is heavier than a solid axle. If you just want something to handle better around town, like you want, then IRS would be a good thing to have. However, wheel hop is still an issue on the street. Wheel hop has really been getting on my nerves lately. I actually broke a halfshaft because of wheel hop....with less than 5,000 miles on my car.

I used to own a 00 GT before my Cobra and I will tell you that IRS handles way better than a solid axle. It's night and day. I specifically remembered certain bumps in certain roads because the GT solid axle bothered me so much. I hated how the car would "kick out" when I hit an uneven part in the road. With IRS, the car doesn't skip a beat. Bumps that would make the GT feel like it was about to spin around, the Cobra just keeps on moving right along.

You say you want it for just normal driving, then I think you will be happy with the IRS.

Good luck.