Fox Mustang: IRS swap

Builds
1

Looking to gear my car for some more enjoyable street driving with road coarse track days on my mind, I swapped in an IRS from an '03 Cobra into my '93 Mustang LX. When I initially put the car together some 10+ years ago, I had some interest in the 1/4 mile as well as turning and stopping, but never committed heavily towards one over the other. The resulting set up sucked…drag oriented control arms on solid bushings mixed with lowering springs and stock shocks and struts. Not good.

I also like the idea of bringing more modern tech into older cars:tup:

The car:

http://i84.photobucket.com/albums/k21/deener50/Mustang/Orange.jpg
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IRS courtesy of Greg, aka Cobraman04

http://i84.photobucket.com/albums/k21/deener50/Mustang/DSC_0009.jpg
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8.8 solid axle

http://i84.photobucket.com/albums/k21/deener50/Mustang/DSC_0873.jpg
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http://i84.photobucket.com/albums/k21/deener50/Mustang/34356_1532495196425_1356146522_31495400_5869626_n.jpg
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The SN95 Mustangs (95-04)were the last iterations of the Fox platform that dates back to 1979. For the most part the IRS aligns with the Fox mounting points. Here’s the Fox untouched:

http://i84.photobucket.com/albums/k21/deener50/Mustang/DSC_0005.jpg
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…and with the snubbers and rear quad shock bracket removed. The holes remaining from the shock mount will be used to align the IRS bracket. The front of the IRS cradle simply bolts to where the 8.8 lower control arm was.

http://i84.photobucket.com/albums/k21/deener50/Mustang/DSC_0007.jpg
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---------- Post added at 12:23 AM ---------- Previous post was at 12:17 AM ----------

With the front bolts holding the IRS in place, the entire cradle was pivoted upwards to bring the brackets to the frame rail, barley noticable where the hit of red bushing is exposed. Gas tank was removed for easier access to all this…

http://i84.photobucket.com/albums/k21/deener50/Mustang/DSC_0021.jpg
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Some holes needed to be made as only one Fox location was perfectly lined up (not shown in this pic). Excuse the washers as I have to track down stronger hardware, at a more appropriate length.

http://i84.photobucket.com/albums/k21/deener50/Mustang/DSC_0011.jpg
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…and here it is pretty much mocked up in place.

http://i84.photobucket.com/albums/k21/deener50/Mustang/DSC_0018.jpg
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Gonna run this look…hopefully it won’t rub!

http://i84.photobucket.com/albums/k21/deener50/Mustang/DSC_0012.jpg
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2

Awesome!

I love fox bodys. :tup:

3

Nice!

4

The IRS houses factory 3.55 gearing, this marks the 4th gear swap that my car has seen! Picked up a new speed sensor while all was apart, I was having some issues with mine…

http://i84.photobucket.com/albums/k21/deener50/Mustang/DSC_0089.jpg
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Had to run all new brake lines as the Cobra brakes run a metric fitting at the caliper, and the Fox line is standard. The orientations are also much different…so I just went from midpoint of the car and ran all new line. Used a coat hanger to get the ballpark shape, then bent all the lines by hand.

http://i84.photobucket.com/albums/k21/deener50/Mustang/DSC_0002.jpg
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Here’s where the single line splits off to each caliper.

http://i84.photobucket.com/albums/k21/deener50/Mustang/DSC_0032.jpg
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Went to bleed the brakes…fluid everywhere. Here’s my lesson to you, be careful about what fittings you buy. I wasn’t. I went to Advance Auto blindly thinking a brake fitting is a brake fitting, how can this be low quality!? Well, come to find out the Chinese shit has MUCH lower tolerances, so much that a healthy seal was damn near impossible! *Note the size and shape of the cone between these two fittings. It should be obvious which one will seal best. The other bit to mention here is that my shitty brake flaring tool wasn’t up to par and was not allowing me to get a proper flare.

http://i84.photobucket.com/albums/k21/deener50/Mustang/DSC_0037.jpg
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Here you can faintly see the 270 degrees or so of interference made by the brake flare…no good.

http://i84.photobucket.com/albums/k21/deener50/Mustang/DSC_0052.jpg
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Replaced all fittings with US grade pieces from Capriotto Auto Parts, along with new flares courtesy of a borrowed higher quality tool…and the brakes are golden.

Speaking of golden…I opted to refresh the look of the calipers by going with a copperish/oragish/goldish look as red was old news.

http://i84.photobucket.com/albums/k21/deener50/Mustang/DSC_0017.jpg
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Fronts…rotors turned and painted

http://i84.photobucket.com/albums/k21/deener50/Mustang/DSC_0009-1.jpg
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Pretty much what the car looked like, and where it sat, for about a month during this amazing summer:(

http://i84.photobucket.com/albums/k21/deener50/Mustang/DSC_0004.jpg
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---------- Post added at 12:58 AM ---------- Previous post was at 12:43 AM ----------

Moving onto the exhaust, the IRS has a different configuration than the 8.8 Fox. New mufflers were needed since the Cobra is a center exit, Fox exit is offset to get the tailpipe to each corner by going up and over the axle on either side of the differential.

While the new muffs were on order, I got to cleaning up the Magnaflow tailpipes that I also picked up off of Greg. They are stainless, and had a healthy discoloration to them. (The pipe on the right has been cleaned…)

http://i84.photobucket.com/albums/k21/deener50/Mustang/DSC_0086.jpg
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I just happened to have a gallon of acid that worked great for bringing this back to life. Here’s what a few drops did just a few seconds after contacting the pipe:

http://i84.photobucket.com/albums/k21/deener50/Mustang/DSC_0084.jpg
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Soaked a rag and about a minute later the entire pipe was done. I also took of the 3 1/2" tips as those are just too much for the little butt on the Fox.

http://i84.photobucket.com/albums/k21/deener50/Mustang/DSC_0087.jpg
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New muff hung with modified hangers. The Cobra and Fox have different mounts, so this was a pretty easy solution. Stock piece on left, bent it to hang the muffs at the proper height.

http://i84.photobucket.com/albums/k21/deener50/Mustang/DSC_0019.jpg
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Hung. Spintech mufflers replaced the MAC Flowpaths that I had grown o so fondly of…but it was time to try something new. The walls within the chamber are arcs, rather than straights, and give a little more distinctive and aggressive sound. After a few miles on these, I dig em!

http://i84.photobucket.com/albums/k21/deener50/Mustang/DSC_0055.jpg
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Love the 90 degree bends…this is the dead giveaway that an IRS lurks underneath.

http://i84.photobucket.com/albums/k21/deener50/Mustang/DSC_0057.jpg
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http://i84.photobucket.com/albums/k21/deener50/Mustang/DSC_0062.jpg
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5

:tup:
love it.

6

One of the nicest fox mustangs I have seen around here for sure. This is just how I would do up a mustang… Keep it up…

7

Nice little swap

8

Awesome. Quite a few cobra guys do the opposite swap for better launches, and it isn’t easy.

9

Damn that’s nice and dumped :tup:

10

Looks great Mike. :tup:

11

how much better does it handle now? when are you going to get to the track next?

12

More PictureS!!! Looks awesome

13

Thanks y’all for the kindness.

I can’t get over how much more enjoyable the car is to drive. Shit roads aint no thang now…gone is the roughness, the jolting, the skipping over bumps in a turn. It’s awesome. I was really starting to lose interest in this car prior to this…but now I have found a new love in the twistys. Nice little stretch of road on my way to work has been fun to play on:) My goal was better street manners, and so far with a stock IRS I’m satisfied…can only imagine how much better it can get when I pull the trigger on a nice coil over setup, tubular front end, move the battery to the back, etc. Not sure what the weight balance is now, but I’d like to see how much I can pull off the front to get closer to the 50/50 number.

Track…most likely next year I can get introduced to it. Need tires yesterday…and would like to figure out exactly what I want to do with the rest of the suspension before I can get out there.

14

What do you expect it to run?

15

Financially??? In my limited research…through Maximum Motorsports they have a nice coil over set-up specific to Fox Mustangs with IRS that runs $1700. Add $500 for the IRS upgrades to beef that shit up (will have to dig up a link with what this entails).
Would also like to find an extra set of wheels to run track rubber…so figure, what…$1000 for that?

16

Mike the IRS is upgraded it has poly bushings all around the only strip you could do is replace those with aluminum ones

17

Dude thats bad ass. I have always loved foxes!

18

cool project… how heavy is this thing?

19

True…as well as it had the the diff brace. Forgot to mention that…good looking out!

Car was ~3200 before this swap. I’ve read the IRS adds anywhere between 75-150lbs. Despite the additional weight, the car is MUCH more balanced now and turns and brakes with much more confidence. For the most part, my car is at full weight (stereo, AC, big wheels, etc.).

20

I was talking times lol… is it fast