1999 Cobra IRS

9986paulk · March 29th, 2011, 08:34 PM

Hey guys I just kinda wanted to see what people thought of the IRS. I have the opportunity to get the complete setup for $325, but is it a direct swap, will I run into issues with stuff like wheel hop, is it really worth it considering the suspension stuff costs more, how much power they can take? Any info would be great. I finally found a semi local guy that can get me that or a solid for less, maybe even with gears.

ESG-642T · March 29th, 2011, 08:44 PM

IRS is awesome,
after you dump some serious coin into it.

9986paulk · March 29th, 2011, 08:55 PM

How much are we talking? And like what? You're exactly the guy I was hoping would come in on this. Cause I don't think $325 is too bad for it.

SlowSix · March 29th, 2011, 09:03 PM

My buddy has IRS on his six. He likes it, but they hold less power than a SRA. Not sure what is involved in the swap exactly. Your car will definitely be a less bumpy ride with it, but you're also looking at more weight and probably an easier rear end to break than an SRA.
I can ask him about it if you want me to.

Just note that you will also need to get an IRS catback exhaust...the regular exhaust won't fit

9986paulk · March 29th, 2011, 09:08 PM

Good point, I'm not changing the exhaust too. Nor do I want to really have to dump more money into it than I have to to get it to hold 500 or so.

SlowSix · March 29th, 2011, 09:14 PM

Yeah, you're probably looking at atleast 300 to get an IRS catback to go with it.
Found an EGR mount for that windstar btw. Thumbs up.

SALEEN961 · March 29th, 2011, 09:25 PM

So where is this IRS for $325, I don't mind changing out my exhaust.

Mineral_Grey_Gt · March 29th, 2011, 09:25 PM

Getting rid of all the rubber from the IRS is a key point to reducing wheel hop

You can get a complete bushing kit for around 675.00

mustangmike! · March 29th, 2011, 11:23 PM

Many irs people swap for a built 8.8

A great rear for you will be 8.8 31 spline. IDK whats the best diff, but 7.5 is detriot, so maybe that diff for a 8.8.
Get a Girdle for it.

and get teh quad shocks for it as well. A rear sway, and sub frames. You'll be good to go.

BlueScreaM · March 29th, 2011, 11:56 PM

They look nice

As far as power it can take id post in the 4v section.

southfour! · March 30th, 2011, 01:16 AM

the only thing that i know about the cobra IRS's is that apparently the 99 is the weakest of them all.

ESG-642T · March 30th, 2011, 02:03 AM

Well to give you an idea....

One guy in town has a kb cobra that was making 666rwhp, he broke the LV5 halfshafts that are like 6-800$ and this is a car with a completely built irs.

Upgrade the busings spend about 650-1000$ doing that, and a brace / diff housing.

And just hope the axle shafts like you

southfour! · March 30th, 2011, 02:40 AM

Originally Posted by ESG-642T

Well to give you an idea....

One guy in town has a kb cobra that was making 666rwhp, he broke the LV5 halfshafts that are like 6-800$ and this is a car with a completely built irs.

Upgrade the busings spend about 650-1000$ doing that, and a brace / diff housing.

And just hope the axle shafts like you

yeah that would get expensive real quick.

Alexander III · March 30th, 2011, 08:35 AM

Not worth it IMO.

Why do you want to go with IRS? As mentioned it will be heavier, expensive, and might/ will have problems.

WickedSnake00 · March 30th, 2011, 10:30 AM

IRS handles awesome.

You will need a new exhaust though, and yes, the 99's were the weakest. One of the added bonus's is that the Cobra axles are geared to 3.55:1.

But at your power levels you shouldn't have to worry. The guys snapping things are 600+rwhp Cobra's, and that's usually launches at the track with drag radials. Not a V6 on street tires cruising around town. I've got a V8 and 245's and I have yet to have a problem, even with agressive launches. In any case good bushings and an IRS brace kit will solve your problems.

At any rate, that price seems like a steal. Just be aware that it could be a MKVIII IRS. The difference is the MKVIII used 28 spline axles vs 31 on the Cobra, and I believe had the 3.27:1 axle ratio, otherwise they were identical.

2000stallion · March 30th, 2011, 11:28 AM

Actually a twin turbo v6

WickedSnake00 · March 30th, 2011, 11:49 AM

Well then. What HP/TQ level? It seems to be when you break 600hp/tq that it begins to become a problem.

Not to mention it's important to mention these are typically with twin screw superchargers that are already putting out massive torque numbers down low, versus a turbo which develops peak torque much later. I imagine that turbo launches (save fully spooled auto with a transbrake) would not be as harsh on it as a twin screw.

1999cobra92 · March 30th, 2011, 11:50 AM

If you want to have the IRS problem free all you need to do is upgrade subframe bushings, diff bushings, and control arm bushings, good stiff springs in the back and if you break an axle then that when you get a 31 spline diff and oem 04 cobra half shafts

1999cobra92 · March 30th, 2011, 11:53 AM

Also I'm in the 350 rwhp range with nitto555 and I have 0 problems with my set up. Check my garage for modds

9986paulk · March 30th, 2011, 06:13 PM

Thanks for all the responses guys. And I do know the rear is from a Cobra, the guy is always parting out wrecked Mustangs. And for the record, I wasn't looking to get an IRS, I was just looking for an 8.8 rear to build and this guy mentioned he had a 99 Cobra IRS for $325.

I won't make more than low 400s at most on my TT 6. But I'll put it around 550 next year with the 4.6. So it's something I need sooner or later. A sof now I'm just waiting for the guy to get in a solid 8.8.

March 29th, 2011, 08:34 PM	#1
9986paulk Hardcore Enthusiast 1999 Mustang V6 Join Date: Dec 2008 Location: Youngstown Posts: 1,226 iTrader: 3 reviews	1999 Cobra IRS Hey guys I just kinda wanted to see what people thought of the IRS. I have the opportunity to get the complete setup for $325, but is it a direct swap, will I run into issues with stuff like wheel hop, is it really worth it considering the suspension stuff costs more, how much power they can take? Any info would be great. I finally found a semi local guy that can get me that or a solid for less, maybe even with gears. __________________ Twin Turbo

March 29th, 2011, 08:44 PM	#2
ESG-642T [8MINUS2] 2002, Ford, v6 Join Date: Feb 2007 Location: TEXAS Posts: 12,319 iTrader: 0 reviews	IRS is awesome, after you dump some serious coin into it. __________________ Hi, You can call me Kyle Random ESG fact: Had a prochamber on his v6 before it was popular. WTB: v6 BBK valve covers

March 29th, 2011, 08:55 PM	#3
9986paulk Hardcore Enthusiast 1999 Mustang V6 Join Date: Dec 2008 Location: Youngstown Posts: 1,226 iTrader: 3 reviews	How much are we talking? And like what? You're exactly the guy I was hoping would come in on this. Cause I don't think $325 is too bad for it. __________________ Twin Turbo

March 29th, 2011, 09:03 PM	#4
SlowSix Formerly 01silversixer 2001 V6 15.47@89.57 Join Date: May 2010 Location: Pittsburgh, PA Posts: 3,471 iTrader: 1 reviews	My buddy has IRS on his six. He likes it, but they hold less power than a SRA. Not sure what is involved in the swap exactly. Your car will definitely be a less bumpy ride with it, but you're also looking at more weight and probably an easier rear end to break than an SRA. I can ask him about it if you want me to. Just note that you will also need to get an IRS catback exhaust...the regular exhaust won't fit __________________ Build Thread

March 29th, 2011, 09:08 PM	#5
9986paulk Hardcore Enthusiast 1999 Mustang V6 Join Date: Dec 2008 Location: Youngstown Posts: 1,226 iTrader: 3 reviews	Good point, I'm not changing the exhaust too. Nor do I want to really have to dump more money into it than I have to to get it to hold 500 or so. __________________ Twin Turbo

March 29th, 2011, 09:14 PM	#6
SlowSix Formerly 01silversixer 2001 V6 15.47@89.57 Join Date: May 2010 Location: Pittsburgh, PA Posts: 3,471 iTrader: 1 reviews	Yeah, you're probably looking at atleast 300 to get an IRS catback to go with it. Found an EGR mount for that windstar btw. Thumbs up. __________________ Build Thread

March 29th, 2011, 09:25 PM	#7
SALEEN961 Regular 1999 V6 Mustang Join Date: Feb 2011 Location: Wayne, PA 19087 Posts: 272 iTrader: 0 reviews	So where is this IRS for $325, I don't mind changing out my exhaust.

March 29th, 2011, 09:25 PM	#8
Mineral_Grey_Gt Regular 2002 Mustang GT Join Date: Mar 2011 Location: California Posts: 420 iTrader: 0 reviews	Getting rid of all the rubber from the IRS is a key point to reducing wheel hop You can get a complete bushing kit for around 675.00

March 29th, 2011, 11:23 PM	#9
mustangmike! I Post Entirely Way Too Much 2004,1994,1967 14.37 @ 96 Join Date: Aug 2008 Location: Texas Posts: 6,018 iTrader: 1 reviews	Many irs people swap for a built 8.8 A great rear for you will be 8.8 31 spline. IDK whats the best diff, but 7.5 is detriot, so maybe that diff for a 8.8. Get a Girdle for it. and get teh quad shocks for it as well. A rear sway, and sub frames. You'll be good to go. __________________ 227whp N/A V6 Now w/ 8th Mile 8s ! How To Jmod Your Late Model 4R70W

March 29th, 2011, 11:56 PM	#10
BlueScreaM MM Fanatic Better than ONLYaUNCfan's 2012@lightspeed Join Date: Aug 2010 Location: Columbia, SC Posts: 3,368 iTrader: 0 reviews	They look nice As far as power it can take id post in the 4v section. __________________ Formerly, AhobosCheese and Cheddars.

March 30th, 2011, 01:16 AM	#11
southfour! Not Banned 2000 Mustang V6 2000 Silverado 1500 Join Date: Jan 2010 Location: Calgary, Canada Posts: 4,552 iTrader: 3 reviews	the only thing that i know about the cobra IRS's is that apparently the 99 is the weakest of them all. __________________ H/C/I V6 BMC Member: 12521 Cam Video My Build Thread

March 30th, 2011, 02:03 AM	#12
ESG-642T [8MINUS2] 2002, Ford, v6 Join Date: Feb 2007 Location: TEXAS Posts: 12,319 iTrader: 0 reviews	Well to give you an idea.... One guy in town has a kb cobra that was making 666rwhp, he broke the LV5 halfshafts that are like 6-800$ and this is a car with a completely built irs. Upgrade the busings spend about 650-1000$ doing that, and a brace / diff housing. And just hope the axle shafts like you __________________ Hi, You can call me Kyle Random ESG fact: Had a prochamber on his v6 before it was popular. WTB: v6 BBK valve covers

March 30th, 2011, 08:35 AM	#14
Alexander III Absens haeres non erit '11 Performance Package 4.61@356.68 Join Date: Dec 2007 Location: Atlanta Posts: 2,817 iTrader: 0 reviews	Not worth it IMO. Why do you want to go with IRS? As mentioned it will be heavier, expensive, and might/ will have problems. __________________ Current: '12 VW CC Sport 6MT \| '10 Jetta TDI \| '08 350Z Vert \| '95 S14 \| '85 325e BUY MY SCT X3 UNLOCKED USED TWICE

March 30th, 2011, 10:30 AM	#15
WickedSnake00 MM's king of Neon's 404 - car not found 17.81@87 Join Date: Aug 2010 Location: Diesel Engine Capital of the World, Columbus, IN Posts: 7,376 iTrader: 0 reviews	IRS handles awesome. You will need a new exhaust though, and yes, the 99's were the weakest. One of the added bonus's is that the Cobra axles are geared to 3.55:1. But at your power levels you shouldn't have to worry. The guys snapping things are 600+rwhp Cobra's, and that's usually launches at the track with drag radials. Not a V6 on street tires cruising around town. I've got a V8 and 245's and I have yet to have a problem, even with agressive launches. In any case good bushings and an IRS brace kit will solve your problems. At any rate, that price seems like a steal. Just be aware that it could be a MKVIII IRS. The difference is the MKVIII used 28 spline axles vs 31 on the Cobra, and I believe had the 3.27:1 axle ratio, otherwise they were identical. __________________ Official Secondhand Snake Build Thread Here Looks Like a Cobra, Sounds Like a Cobra, Tastes Like a Cobra, Not a Cobra. For Sale: P71 Interceptor motor

March 30th, 2011, 11:28 AM	#16
2000stallion Hardcore Enthusiast 2000 Mustang slow@slow Join Date: Oct 2009 Location: Kansas Posts: 2,000 iTrader: 1 reviews	Actually a twin turbo v6 __________________ For Sale: 99-04 smoked tail light covers 2000stallions Build Thread

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March 30th, 2011, 11:49 AM	#17
WickedSnake00 MM's king of Neon's 404 - car not found 17.81@87 Join Date: Aug 2010 Location: Diesel Engine Capital of the World, Columbus, IN Posts: 7,376 iTrader: 0 reviews	Well then. What HP/TQ level? It seems to be when you break 600hp/tq that it begins to become a problem. Not to mention it's important to mention these are typically with twin screw superchargers that are already putting out massive torque numbers down low, versus a turbo which develops peak torque much later. I imagine that turbo launches (save fully spooled auto with a transbrake) would not be as harsh on it as a twin screw. __________________ Official Secondhand Snake Build Thread Here Looks Like a Cobra, Sounds Like a Cobra, Tastes Like a Cobra, Not a Cobra. For Sale: P71 Interceptor motor

March 30th, 2011, 11:50 AM	#18
1999cobra92 Enthusiast 1999 mustang cobra Join Date: Aug 2010 Location: Los Angeles, Ca Posts: 882 iTrader: 1 reviews	If you want to have the IRS problem free all you need to do is upgrade subframe bushings, diff bushings, and control arm bushings, good stiff springs in the back and if you break an axle then that when you get a 31 spline diff and oem 04 cobra half shafts __________________ Black and White Crew Crew Member # 5 Check garage for mods and pics if you Los Angeles and want to ride send me a text (323) 270-6827 0% Wheel hop, 0% broken parts, 100% wheel spin

March 30th, 2011, 11:53 AM	#19
1999cobra92 Enthusiast 1999 mustang cobra Join Date: Aug 2010 Location: Los Angeles, Ca Posts: 882 iTrader: 1 reviews	Also I'm in the 350 rwhp range with nitto555 and I have 0 problems with my set up. Check my garage for modds __________________ Black and White Crew Crew Member # 5 Check garage for mods and pics if you Los Angeles and want to ride send me a text (323) 270-6827 0% Wheel hop, 0% broken parts, 100% wheel spin

March 30th, 2011, 06:13 PM	#20
9986paulk Hardcore Enthusiast 1999 Mustang V6 Join Date: Dec 2008 Location: Youngstown Posts: 1,226 iTrader: 3 reviews	Thanks for all the responses guys. And I do know the rear is from a Cobra, the guy is always parting out wrecked Mustangs. And for the record, I wasn't looking to get an IRS, I was just looking for an 8.8 rear to build and this guy mentioned he had a 99 Cobra IRS for $325. I won't make more than low 400s at most on my TT 6. But I'll put it around 550 next year with the 4.6. So it's something I need sooner or later. A sof now I'm just waiting for the guy to get in a solid 8.8. __________________ Twin Turbo

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