I have a V6 03' mustang but i want the best handling i can get so i wanna know what it takes to change out my live axle for the cobras IRS?

 

Here is a pretty good write up from another forum http://www.3.8mustang.com/forum/show...light=IRS+swap

 

about 4 hours, new ABS sensors which are a bitch to find, brake hoses, driveshaft, cat-back.

 

abs can be reused, breaks are fine since the 99-04 mustangs use the same rear brakes, driveshaft can be used but you need to get some sort of u-joint or something.

http://www.angelfire.com/bug/irs0/

 

I have to wonder about the gain here...In a CAR & DRIVER comparo test, the Mustang gave better skid pad numbers than either the new Camaro or the Challenger, both of which have fully independent suspension. Might be cheaper and a lot less labor to work with what you have. (edit) They were comparing 2010 models...

 

Well I'm pretty sure you can get just as good of handling (performance wise) with a SRA as you could with a IRS or else the AIX guys would all swap. What you do get with the swap is great handling with a comfortable ride.

 

not correct. The GT abs sensor cables don't reach. Trust me, I've done this a few times. You can't route them correctly/safely using the GT cables. The cobra cables are somewhat hard to find sometimes.

The driveshaft needs to be either shortened by about an inch (5/8 - 1" varies) to 43.5" or replaced with a stock IRS cobra driveshaft. The yoke from the cobra ds needs to typically be replaced with the one from the GT driveshaft as well as the rear flange. I've gotten away with leaving the rear flange from the cobra and just replacing the slip yoke on the tranny side.

A solid rear with a good setup will out perform the IRS. The IRS doesn't stand a chance simply because the mustang IRS sucks *** as IRS's go and there's no amount of band-aids that will make a sows ear into a silk purse. The pumpkin dynamically loads and unloads especially as you use throttle modulation which causes traction issues and breakage, the rear chassis mounts are mounted in single shear with a compliant bushing and the front chassis mounts are similarly squishy bushed, neither is a damn bit good for handling and leads to some erratic rear wiggles. The pumpkin itself has a tendency to flex under loads (I've broken them driving hard because of this) and the rear covers blow up like there's no tomorrow because of it. Even with every bit of 2K in upgrades to the thing there's only so much it'll take before it suffers a MAJOR breakage and you're not just stuck but stuck with a big *** repair bill.

My current SRA setup with the MM PHB/TA and coil overs is light years ahead of my old IRS setups in handling. Especially just after you've passed the common sense speed to be taking any particular corner at.

EDIT: the new mustang uses a 3 link and panhard setup that's similar in principle to the tq arm and panhard bar setup I use but a lot more compact and with a few technical ramifications I won't bore you with. It's a great setup out of the box but needs a little work on the springs and sways and better control arms to really shine. After that... **** I'd leave it alone. They really do handle surprisingly well right out of the box if you're aggressive on the throttle.

 

I personally believe the IRS has it all over the stick axle for handling. What would make the stick axle more appealing would be massive amounts of HP, which would reduce reliability, or being used on a flat racing surface.
The arguement was made that if the IRS was so good the AIX guys would be using them, I'm saying that they won't use them because of HP (reliability), they usually run on a maintained surface, the AIX guys can also remove the abortion mustang rear susepnsion and replace it with something else, and lastly but most importantly the IRS adds about 80 pounds to the vehicle. In a drag racer the point is moot, the stick wins every time. But in a stock or near stock mustang the stick axle rearend is such a complete and utter disater with all of the suspension arcs competing with each other and also keeping the rearend in almost a perpetual bind, that the IRS is the way to go.
In any case here's a link to my swap, I think it covers most of the questions.
http://www.tamparacing.com/forums/fo...tick-axle.html

 

I don't see how adding 80lbs is a good thing if thats what you meant. I somewhat agree TA and PHB>IRS>stock triangulated four link.

 

if the IRS was worth a damn the AIX guys would use it. Only Kenny Brown has significantly improved the stock IRS and his stuff is kinda race oriented and fragile in its own right. Face it, you can't make a silk purse from a sows ear. As an aside, I'll put my TA/PHB setup against an IRS mustang any day. And no, big power is not the solution for either. It's useful but not necessary. I've raced my car with both setups... the MM 3 link is vastly superior.

 

Don't take it out of context, the IRS is a loser for drag racing, both weight, complexity and the affinity to wheel hop guarantee that.
This is not a stock or near stock application, you've canned the awkward 4 link and replaced it with something better, and lighter
You spend your money, I'll spend mine

 

It is my opinion that the Tq. Arm/PHB 3 link is superior to the IRS, thats why I have gone that direction. But, the MM 3 link is highly modified stock live axle, and that the IRS is superior to the stock axle setup. The OP is wanting to go from a stock stick axle to an IRS, which is a mound of improvement. The OP has a 7.5" axle, which would need to be replaced with an 8.8" to even upgrade to the 3 link which, in a way, ruins the 3 link argument. I would rather see him go with an 8.8" -> PHB -> Tq. Arm, but I see no problem going 7.5" -> stock IRS. I think it would be easier, and cost a similar amount in the end.

I think that is a bit of both arguments rolled into one.

 

No one said the stock triangulated 4 link was better. What was said was that you can MAKE the solid axle perform better than the IRS set-up.

 

so far its sounding better to just upgrade my solid axle so i dont have to worry about havin IRS problems if i add too much HP, but theres gotta be some way to improve on the IRS to be reliable and handle great with high HP.

and what kinda power does it take before the IRS starts taring up the dif cuz i wanna go about 6 or 7 hundred HP eventually.

 

I fragged mine 3 times making only 244/281 and it had been upgraded repeatedly trying to make it reliable. It will never handle that well ... the rubbery bushings and flexi carrier assure that but it will always handle better than a stock dual triangulated 4 link

 

I am not trying to take anything out of context. I just misread your statement.

 

Problem is the IRS pumpkin is Aluminum. It becomes a matter of not if but when will it grenade due to Aluminum's short fatigue life. The way to fix it would be if the aftermarket came out w/ a beefier one or an Iron one. Now MM does have a good suspension package for it, but it's cheaper to stick w/ the stick and to upgrade it since an upgraded IRS is only at the same level as a SATBPB set-up, maybe slightly better than the stick in the turns.

 

if you want to make it stronger then grab the iron centersection from a Tbird Supercoupe or XR7 (v8 cars) with IRS. The T-bird used an IRS that's partially compatible, well... the centeresection works. Just be sure that your gear guy doesn't set it up real tight or you'll burn it up.

I did that to my IRS and the centersection never broke again, after that it started breaking half shafts and rear covers which were easier and cheaper to replace.

 

I am not sure how hard red drives his car, but the IRS can take hp, hp alone will not break it, tons and tons of 03/04 cobra guys still have the irs w/ upwards of 600+hp to the wheels. What is going to beat the rear end up is going to be long term abuse(such as heavy road racing where the rear will build up lots and lots of heat) but even then I have seen many guys continue to race the IRS with no problems. Not saying red's info isn't correct but it is one person's opinion. I personally love the IRS find it to be far more responsive and planted in it's handling characteristics then the stick axle. If upgraded w/ halfshafts, a heavier duty t-lock differential, and replacing of the bushings with derlin bushings along with a spings/coil overs/shocks/struts/irs bracing etc. that it can easily match any level of performance you will get out of the stick axle if not surpass it. Just my opinion.

 

I drove it hard and raced it hard (track and street) and maintained it like a madman. The weakness in the design could not be got around to my standards. I put thousands of bucks into upgrades (all the bushings, iron center section, diff cooler, 31spline diff and shafts, rear cover brace, tie rod ends, coil overs, double shear rear upper bracket mod, etc... basically the whole of MM's IRS offering). It handled really well until you got to the limit and then it was all the time doing erratic ****.

A swap to the tq arm/phb setup made the car a good bit looser but also a lot more predictable and it SHOOTS out of corners now rather than squirting out in a random direction after the rear end finishes wiggling like J-Lo's *** (subtle difference, one is violent and controlled, the other is violent but directionally random kinda like a fire hose on the loose) like the IRS did.

I know one thing, I've never broken my stick axle, not once. No damage requiring any sort of repair. The IRS cost me 3200 bucks in 1 year in repairs alone. Add the 2 grand plus for the upgrades and you see that you can have a FULL MM max grip box on a live axle installed for the same price as I spent just trying to use the IRS and you'll have a more capable car.

I hand IRS asses to the owners of said rides at auto-x events. All of the benefit of both systems is non-binding articulation and smooth arcs of movement. I know of 1 IRS driver that's good competition for me but he's a genuine bad-*** and smokes me on raw skill.

If you don't race, grab an IRS if you like. Just don't get into it because you are under the false impression that a live axle can't handle. I MADE THAT MISTAKE FOR YOU. I was ignorant and thought that the IRS could not be beat for handling and I was WRONG. My car now handles WAY better but I have to be a much much more attentive driver or it's real easy for it to get away from me.

I otherwise tend to agree with mv6. It's not terrible but just not that good.

 

Hey Red how do the IRS and the TQ arm/PHB setup compare in street comfort.

 

Of course hp will break it, just how many Cobra owners are using all of their 600 hp on the street. 600 hp is even too much for an 8.8. At that point, I'd consider a 9" or better. What kills the system isn't so much the heat (as that'll fry the trac-lock) but more so the Aluminum components due to their limited fatigue life (plus weaker strength). That's why I bet more Cobras die at the strip than they do in the turns, since the strip is the ultimate test in fatigue life. It maybe fine for the street but for a muscle car, if it's going to be driven as such, the IRS is the wrong way to go.

 

TQ arm setups are quite frankly a little firm feeling even with street springs in the rear. I have more race oriented springs in the rear and it's quite firm. The IRS even with fairly stiff springs in it (still race oriented) was pretty comfy. My back liked the IRS, my ***** like the tq arm.

That's kinda the thing I've been getting at. Mustangs are good and strong and while they "can" corner it's not exactly their shiny suit. They're best at using brute force to jerk themselves out of the hole and they're manageable street cars. My car handles with M3's but it's never going to be an M3. That's why I'm building my open wheel car.

 

yea i think i got my answer thanx to all u guys goin back n forth ima stick wit my solid axle.

but say i had the money, you think i could get a custom IRS made?

 

all else being equal, yeah but you'd have to chop up the car pretty good to fix the pumpkin to the frame properly.

 

here is a fairly informative article on the IRS it's weakness, it's strengths and a bit on the solid axle. Covers the basics I would say.
http://www.svtperformance.com/forums...uspension.html

 

^ absolutely a great article, I have found that most guys that don't like the IRS are drag racers. In the case at the top of the forum, this guys is going from a 7.5 stick axle to an IRS which is an 8.8. I have picked up several IRS for $200 to $250 bucks. The dragster guys practically throw them away, and they are easily scrounged. His other alternative is to go with the standard stick axle suspension, which is some real garbage and absolutely causes over steer on corner exit, or go to an MM, Griggs, Steeda type of rear axle assembly that actually functions, which will be way over $500.
So for the V6 guy to go from a 7.5 to an 8.8 IRS, for under $500 is a no-brainer.