workmangc

Hello All, I am compiling all of the info that I have come across in my IRS research. I cannot take any credit for this other than the effort to "steal" it from other sites.

Keith, Perhaps you could make it a sticky or just put them on the Homepage.

workmangc

As presented on www.mightymustangs.net, previously stolen from www.svtperformance.com
Heres what you have to do.

Support the frame on jackstands, use the body not the IRS.
1. Remove driveshaft and rear wheels/tires.
2. Remove parking brake cable
3. Remove tierod end (disconnect inward bolt by differential)
4. Remove Brake caliper and rotor
5. Remove traction control sensors from diff hub
6. Support lower control arms up with jackstands
7. Remove upper<!--coloro:#FF0000--><!--/coloro-->*<!--colorc--><!--/colorc--> and lower spindle to control arm bolts
8. Place a screw driver between the halfshaft and diff gently pry outwards to unseat the halfshaft.<!--coloro:#FF0000--><!--/coloro-->** <!--colorc--><!--/colorc-->To install shaft align splines and slide inwards itll take some effort
9. Support the halfshaft and spindle and pull it outwards from the differential
10. Support the diff with a jack
11. Unbolt the rear diff attach bolts from the diff cover
12. Remove the front attach bolts and bushings, !!Warning!! Diff is no longer attached to the IRS and could fall and cause damage to the diff or injury to you. Support the diff on the jackstand to help balance it.
13. With the diff supported, lower the jack and diff to the floor.
14. Once the diff is out the fluid swap is like any other rear end fluid swap, remove cover, drain fluid, clean gasket surface, install new gasket, torque cover bolts.
Reinstall following the reverse removal steps. Refill diff once its in back in the car. Be sure to add one bottle of FMS friction modifier.


<!--coloro:#FF0000--><!--/coloro-->*Index the upper eccentric alignment washer to the spindle to ensure correct alignment when the spindle is reinstalled failure to do this will result in an unaligned rear end.
**Before removal it's important to index the halfshafts to the splindle to ensure correct reinstallation failure to do this my result in a driveline vibration.<!--colorc--><!--/colorc--><!--QuoteEnd-->

workmangc

This is not my Article....I didn't write it or conceive it. I believe the persons screen name is Snake Eyes from SVTP.

http://www.svtperformance.com/forums...d.php?t=213384

Here are my thoughts on the IRS. This is based on all information I have been able to collect on the 99+ Cobra IRS. I know this is a lengthy read but it is well worth the time as it is intended to answer all technical questions about improving the 99-04 cobra IRS.

The main problem is traction. Thus good tires are a must, and those tires must to be properly inflated to perform correctly. But you also need to keep those tires on the ground (not bouncing) so a good set of shocks and springs are very important. Coil-overs are best but standard (non-coil over) springs are still better than stock. Adjustable shocks are great for those who like to open track or drag, and they can be dialed in to combat wheel hop. I have a Griggs coil-over kit with Koni adjustable shocks myself and I recommend them over MMs IRS coil over kits because Griggs installs spherical joints into the lower eyelets of their shocks where as MM uses polyurethane bushings which over time may fail. If you plan on using OE 03/04 cobra Bilsteins in a coil over application you will need MM's Upper Shock Mount Kit http://www.maximummotorsports.com/shockmount.asp. Also Billetflow manufactures an adaptor kit to use Strange Engineering adjustable shocks with the IRS, http://www.svtperformance.com/forums...d.php?t=144341.

Needless to say subframe connectors are an absolute must, Griggs and Maximum Motorsports sell the best. MM's full length subframe connectors are the standard http://www.maximummotorsports.com/sfc.asp but for those wanting the strongest frame possible go with Griggs through floor frame kit, also recommended for high horse power convertibles. Note they are visible in the car http://www.mustangworld.com/ourpics/...t17/slibs4.jpg but are the strongest mustang frame kit in the world.

The IRS comes with soft rubber bushings (even the 03/04s still use rubber though harder than 99/01s). The subframe bushings must be replaced with polyurethane bushings. You can find them at Maximum Motorsports here http://www.maximummotorsports.com/mmirsu.asp or Steeda here http://www.steeda.com/store/-catalog...r_bushings.htm. The Steeda bushings come with new nuts and bolts, the Maximum Motorsports does not but you can purchase them as extras. This is important because some 03 Cobras came with 12mm bolts in the forward IRS mounts instead of 14mm bolts. This allows the IRS to shift which of course is not good. You can also order the correct bolts and nuts from Ford. The part numbers are W704939-S426 Bolt M14x109 H and W520215-S427 Nut M14 HEX FL. I recommend the Steeda kit because of the lower cost (when including the bolts), they include 4 (grade 10.9) bolts front and rear, and the rear bolts are a pan head design which allow bigger tires to be used without spacers or grinding on the OE bolt. Maximum Motorsports also offers a button head bolt, http://www.maximummotorsports.com/subframebolt.asp.

For those who need additional wheel clearance with replica style wheels (AFS etc.) I recommend these billet wheel spacer from Lightning Force Performance http://www.lightningforceperformance...productID=1168. I personally run 335/30/18 Viper spec Michelin Pilots on 18x10.5 AFS 03 cobra wheels with this spacer and a button head bolt with no clearance problems.

The control arms and differential mount bushings are also rubber and must be replaced with delrin and aluminum. This will keep the IRS components from moving relative to the subframe which now will not move relative to the car giving it a very sure footed feel (like a torque arm and pan hard rod does vs. the 4 link solid). The guy to get them from is ac427cobra (Bruce). His kit is for sale in the market section here http://www.svtperformance.com/forums...d.php?t=260665. Another guy that makes them is Nick Stangcobra93@comcast.net. You can look at the bushings he sells here http://www.aossguns.com/images/bushing/index.htm. Note some minor prep work is needed to install them correctly. That info can be found here http://www.modularfords.com/forums/2...ngs-24961.html. Maximum Motorsports has released delrin control arm bushings, and an aluminum differential mount kit that allows slightly better adjustment of the pinion angle but Bruce's kit will cost you considerably less. The Maximum Mororsports IRS parts list can be found here http://www.maximummotorsports.com/ir...rmbushings.asp. 1999 and 2001 cobras owners will need to purchase an IRS Heavy Duty Crossmember (aka the Diff Ear Brace) to be used with these bushings. I recommend the stock 03 brace, the cheapest place to pick one up is Stang Suspension http://www.stangsuspension.com/store...?idproduct=376.

The rear IRS subframe mounting point attaches to the car using a cantilevered bracket that is prone to flexing under load because the outer half of this bracket is completely unsupported. This flexing causes unwanted alignment changes and contributes to the IRS feeling like it is moving under the car. Billetflow's Cobra IRS Subframe Bracket Kit http://www.billetflow.com/IRS_Brackets.htm keeps the rear mounts from flexing and improves corning stability. Steeda offers a similar kit http://www.steeda.com/store/-catalog...amebracket.htm but the Billetflow kit is stronger.

A shock tower brace improves rigidity and prevents chassis flex over the IRS (highly recommended if you run coil-overs). It is also advisable to weld the brace rather than bolt it in to add strength to the shock towers. If you are running coil overs with a stiff shock (to reduce wheel hop) the increased loads will cause significant stress on the mounts. Braces can be purchased from Hans RaceCraft http://www.hansracecraft.com/product/ford/mustang.htm. Kenny Brown used to make a better brace but they are now out of business but if you want one here is what they look like http://daytonasp.com/ven/kenny%20bro...es/29901B3.jpg.

For cobras that have been lowered Maximum Motorsports makes adjustable IRS tie-rod ends that allow you to move the joint of the tie rod end back in to correct alignment. This is the equivalent of a bump steer kit for the IRS, http://www.maximummotorsports.com/irstr.asp. Note the PHP toe link bars perform this function also (see below).

While you are at it you should replace your rubber swaybar mount bushings with Maximum Motorsports urethane bushings, http://www.maximummotorsports.com/ir...arbushings.asp and install there adjustable end links, http://www.maximummotorsports.com/rsblink.asp. These items will further improve the responsiveness and corning ability of the rear suspension.

Now that you can will be able to plant your rear tires with confidence you may snap you half shafts, Raxles makes half shafts for the 99/01 guys. They can be found here http://www.raxles.com. A set of used 03 half shafts are a cheap upgrade for 01 guys who are near stock power levels. Remember they will not fit the 99s because 99s came with a 28 spline differential and half shafts where as 01s and 03s use 31 splines. If you want the best the Driveshaft shop makes near indestructible half-shafts, check em out here http://www.driveshaftshop.com/MUSTANGC.V..ivnu.

To prevent differential cover breakage you will want to pick up a IRS differential cover brace from Billetflow, http://www.billetflow.com/irs_brace.htm.

Finally it is necessary to have your IRS aligned, see the alignment section below. If possible try to find a shop that can adjust your bump steer and corner weight your car if it is so equipped.

If you follow this list of upgrades you will have an IRS that plants like a solid, handles like a Porsche, rides like a cloud (compared to a similar level 8.8) and is as close to bullet proof as possible.

For very high horsepower cars the rear toe link bars have been reported to flex, and Paul's High Performance makes a set of toe link bars that look like Honda half shafts http://secure-order-area.net/paulshp...id=8565 _7545. Also these bars eleminate the need for the MM adjustable IRS tie-rod ends. Those wishing to go to the track I would recommend you upgrade your differential. There are many to choose from and that is a separate subject. You can also skip the polyurethane subframe bushings and install aluminum subframe bushings from Sean Hyland Motorsports http://www.seanhylandmotorsport.com/...1865db2a8aca2e. Also the stock spindle bearings will wear prematurely under track conditions and you may want to consider DownUnder Performance's spherical spindle bearings, http://corner-carvers.com/forums/showthread.php?t=24358. Sean Hyland's also makes a set but they are much more expensive, http://www.seanhylandmotorsport.com/...1865db2a8aca2e. A differential oil cooler is also recommended for those who frequently run open track events, I would make one yourself since the kits I have found are over priced. The parts list for the 2000 Cobra R diff cooler can be found here http://www.svtperformance.com/forums...d.php?t=268669. And Finally for those wanting to reduce unsprung weight, Kenny Brown used to make tubular upper and lower IRS control arms those these are not recommended for street use and no longer available. He also made a modified IRS cradle but the benefits were minimal and it is no longer available.

=============== Summary ================
#. Item = Function, Importance
1. Tires = Help everything, Absolutely Necessary
2. Shocks & Springs (coil overs) = Reduce hop & improve handling, Highly recommended
3. Subframe Connectors = Reduce chassis flex, Absolutely Necessary
4. Subframe Bushings = Reduces hop and improves stability, Highly Recommended
5. Control Arm Bushings = Reduces hop and improves stability, Highly Recommended
6. IRS Pinion Brace = Reduces hop and prevents failure, Highly Recommended (only needed for 99/01s)
7. Differential Mount Bushings = Reduces hop and prevents failure, Highly Recommended
8. Subframe Bracket = Reduces hop and improves stability, Highly Recommended
9. Shock Tower Brace = Improves rigidity and prevents failure, Recommended
10. Adjustable Tie-Rod Ends = Improves handling, Recommended for lowered cobras
11. Swaybar Bushings = Improves handling, Recommended
12. Adjustable End Links = Improves handling, Recommended for lowered cobras
13. Half Shafts = Prevents failures, Highly recommended
14. Diff Cover Brace = Prevents failures, Highly recommended
15. Alignment = Improves handling and reduces hop, Highly recommended
16. Toe Link Bars = Eliminate toe changes under acceleration, Recommended for high powered cobras
17. Differential = Improves handling, Recommended for drag, auto X, and open track cars
18. Aluminum Subframe Bushings = Further improves stability, Recommended for race only cars.
19. Spherical Spindle Bearings = Further improves stability, Recommended for drag, auto X, and open track cars
20. Differential Oil Cooler = Prevents failure, Recommended for auto X and open track cars

=============== Useful links ===============
Postban's IRS build up article along with IRS drop procedure and torque specs can be found here:
http://www.svtperformance.com/forums...d.php?t=231900

A good mustang suspension article:
http://www.miracerros.com/mustang/t_suspension.htm

An excellent gear, trans and tire calculator can be found here:
http://www.svtoa-atlanta.org/cgi-bin/trans.cgi

A nice article about driveline alignment (no more 80 MPH vibe).
http://home.flash.net/~ivc1/cobra/irsvibes.html

============== Alignment Info ==============
------- Front ------
Camber______1.5º Negative
Caster_______6.5º Positive (Max Allowed While Equal)
Toe_________0.20º Toe In


------- Rear -------
Camber______1.0º Negative
Toe_________0.05º Toe In
Thrust Angle__0.0º


------- Notes ------
Front Caster
Front caster can only be adjusted with aftermarket caster camber plates. I recommend Griggs, Maximum Motorsports and Steeda (the new 4 bolt design only).

Rear Camber
When the wheel is off the ground, and the upper knuckle is loose, the weight of it tends to rotate the wheel towards positive camber of course. Adjusting the eccentric to the max negative camber by rotating the bolt, only goes so far... the upper arm end is slotted on both sides to allow the bolt to adjust, and to get max camber out of it, it needs to be pushed back in the slot further on both sides of the bolt (The bolt will torque down at an angle if you let it, as the eccentric is on the opposite side).


=========== MM on the Mustang IRS ==========
NASA Pro Racing – Interview with Chuck Schwynoch, CEO
Maximum Motorsports, Inc.
June 28, 2006
By Andy Bowman

Q. The #91 MM Mustang is using an IRS rear suspension, what drove you to this decision, how has the effort been going so far?

A. We had a growing number of customers who called us and said that they were not happy with their IRS, and asked us if they should swap in the proven MM Torque-arm/Panhard Bar rear suspension. We couldn't give them a truthful answer until we had done our own testing to directly compare the Ford IRS to a well-sorted Torque-arm/Panhard bar system. Our AI race car had won races, and set track records, so it was the perfect candidate for comparison. We swapped the rear end over to the IRS, with all of the parts we had developed over the previous year on a street-driven 2003 Cobra. We left the front of the car exactly as it was with the Torque arm suspension. We maintained the exact same rear track width, and even swapped over the same brakes, rotors, calipers, and pads, from the solid axle. We then hit the track for testing. By the end of the first day of testing we were 3 seconds under the AI track record at Buttonwillow. With the IRS we had to learn what alignment and bumpsteer settings worked best. That's what testing told us. Without track testing, we really could not have given our customers an honest answer to their questions about the IRS. Even if our testing had shown the IRS to be grossly inferior to a solid axle, we at least would then be able to help our customers make an informed decision about modifying their car. As it turned out, the IRS is superior to a solid axle fitted with a Torque-arm and Panhard bar, in most aspects.

workmangc

As stolen from http://www.mn12performance.com/mn12p...a_install.html

Stock Cobra IRS subframe.



Factory Pinion damper installed on all 2003 Cobra's.
This must be removed when installing the polyurethane differential bushings.
Both nut and bolt head require 18mm deep socket and box wrench to remove.

The new bushings will be installed where the arrows indicate.

Installation on the Mustang is very much the same as the Thunderbird installation.

Then tighten the nut to 30-40 ft lb MAX to set proper bushing preload.
Note: Overtighting the nut will cause the sleeve to cut into the washer.
Tools Needed:

• Jack and Jack Stands
• 15mm open end wrench (18mm cobra)
• 21mm deep socket (18mm cobra)
• 6" extension
• Torque wrench

workmangc

Billet flow IRS Differential brace install: http://www.svtperformance.com/forums/showt...572#post4281572

workmangc

http://www.svtperformance.com/forums...d.php?t=260665

Complete IRS bushing package

workmangc

All of this was performed with the car on a lift.

I would advise pre-lubing all suspension parts with WD40 or something similar a few days prior to doing this…..I did it, and still had problems with some fussy hardware, I can’t imagine what it would be like without it.
<O</O
Keep the car in gear so you can easily remove the Drive shaft bolts later.
<O</O
Remove Rear seat, by pushing in buttons on each side, just under the front lip of the seat. Feel for them and you will find them.
<O</O
Disconnect the ABS sensors at the plug that is located on each side under the seat. Then push the Rubber grommet on the ABS sensor out through the bottom of the floorpan. Leave them attached to the solid rear, you won’t re-use them. You will need the ABS sensors from the IRS unit.
<O</O
Loosen rear wheel lug nuts so you don’t have problems breaking them loose when the car is on the lift.
<O</O
Lift vehicle and remove rear wheels.

With the car in the air, go to each rear wheel loosen and remove the rear Brakes, E-brake cables, and pull the ABS line from inside the frame at each side. Support the Calipers with some coat hanger wire or similar.

Remove Drive shaft bolts with 12pt 12mm wrench or socket, you may have to get back into the car and put the car in Neutral so that you can turn it to get to all DS bolts, putting it back in gear after it is turned. Support DS with coat hanger or wire as well. If you pull it from the rear of the tranny, you’re going to leak fluid everywhere. Note: I used my stock 98 DS. You do not need one from the donor car. I only know of needing a new, shorter DS If you go to a T-56 because the tranny is longer and I have heard the 03/04’s have a different/ larger pinion flange so you may need a different flange if you have an 03 IRS or perhaps you can swap yours over.
<O</O
I did not have to disconnect the rear swaybar. Some may find it easier to drop the rear with the swaybar removed
<O</O
Remove quad shocks and quad shock mounts if equipped. At this point support the rear with a tranny jack. With the rear firmly supported and secured to the tranny jack. Remove the bolts holding the rear shocks to the rear end. With the shocks unbolted you can SLOWLY lower the rear, allowing it to articulate, till fully dropped. At this point I was able to use a little prybar and remove the rear springs.
<O</O
Use common sense, If you feel that there is still a lot of pressure from the spring do not pry it loose. That is some kinetic energy you’ve got sitting there, and you don’t want it flying out at you. Instead drop the rear some more to loosen the spring.

With the springs removed, You can now tackle the Upper and lower control arms. I just unbolted them from the Car and left them attached to the rear end. With a little persuasion from a prybar the control arms can be coaxed to come out from their respective mounting points and then the rear is free.
<O</O
Drop the Tranny jack, and have a buddy help you lift it onto a dolly. In my case I **** near threw out my back trying to manhandle it alone….(thanks VirginiaVenom) Don’t be stupid like me…..this is easily a 2 or 3 person job.
<O</O
At this point you can remove the E-brake cables from the car. It is a pretty straight forward.
<O</O
If the thought of removing the e-brake cable intimidates you…..you don’t need to be doing this. Pay the cash and have someone else do it for you, Or invite some RCMC members to give you a hand. Although RCMC is not a Free Labor pool……If someone’s turning wrenches on YOUR car….your the tool getter, food person, and beer supplier for when it’s done
<O</O
Now, lets turn our attention to the IRS, since that’s why we’re here to begin with. Most people recommend at a minimum replacing the Subframe bushings with some aftermarket type to reduce axle windup/ wheelhop. Let me point out that the bushings are a MAJOR PITA.

I removed mine by drilling holes in them all throughout and removing the metal sleeve. This left me with a decent size hole to provide oxygen to the fire that I was about to put to it. I used a torch and burned out the bushing material, setting them on fire and then letting the rubber burn. Occasionally I would go back with the drill and remove some of the burned rubber so that I speed up the process. Once all the rubber that I could burn was removed, I used a die grinder with a wire wheel to remove all of the material left……This is a long process and this paragraph does not do it justice. Have some water or fire extinguishers handy, the burning rubber will drip, setting whatever it is on, alight.
I used a spray bottle and just put out any offending flames.

Now comes the joy of pushing in new bushings. Since the IRS unit is too large to move and do this with a hydraulic press, I used a ball joint press instead.
<O</O
Lube, lube, lube is the key….that and making sure your bushing sleeve is clean…otherwise you will have a huge issue getting the bushing all the way in.
Understand that a little material will stick out on both sides of the sleeve. When pressing in the new bushing make sure you have a hollow spacer that will allow the bushing to press all the way through. I used a bearing race, on the back side of the sleeve, this allowed the bushing to slide fully into the metal sleeve. If you don’t press it in correctly or fully it can cause increased noise transmission into the cabin and clearance problems while trying to get the IRS mounted. My rear passenger side bushing wasn’t in fully and was catching on the mounting bracket when trying to lift it into place…..the rear had to be dropped and the bushing pressed in fully…..so don’t think that it will do most of the way in….Learn from my mistakes.
<O</O
With the bushings installed turn your attention back to the car, Remove the bump-stop from the car, directly above the pinion. If you don’t it will cause fitment problems…..You don’t want to have to drop the rear after you’ve realized that you didn’t remove the bump-stop.Also, at this point I took the time to replace the fuel filter…..I don’t want to think about doing it once the IRS is in there, save some regret down the road and do it now.

Take the rear IRS mounts and put them into a vice and massage them with a hammer, spreading the flange open some more. This will give you some more clearance when raising the IRS unit to bolt in the rear mounting points. Mount them loosely at the quad shock location, re-using the quad shock bolts (15mm). I didn’t drill holes into the frame and put the 2 additional bolts there….I will have mine welded to the frame for strength. If not welding you will need to have some bolts, nuts and a miracle to get the bolts into the frame. I have seen a write up where someone drilled all the way into the trunk and just used a long bolt but didn’t want to go that route.

Take the IRS unit and place it on a tranny jack. I slid mine from a raised forklift onto the jack, Otherwise it will take 3 people…..2 can do it….but it would suck. Raise the jack, and locate the front points where the lower control arms bolted to the car. Get them installed but loosely tightened. You still have to articulate this thing up to the rear mounting points. At this point make sure all your ABS sensor and E-brake cables from the IRS unit are to the front and not tangled in the IRS…..You don’t want to have to fish these out later. Once again….this doesn’t do the task any justice…..you’re gonna sweat moving the unit around, it’s heavy.

Now things are starting to take shape. Raise the IRS unit until it articulates up to the rear mounting points, If you didn’t get the bushings pressed in fully or spread out the flange on the mounting brackets, you will curse even more. Once it is located correctly bolt it up and tighten all hardware.
<O</O
Now that the IRS is secured into it’s spot we have to re attach everything. First lets start with the E-brake cables. Take them and run them about the same way as the old one was. The difference for me was I used a different oval hole, where the cable goes into the frame, as the cable gets fed from the rear to the front……don’t stress this at all. It was about an inch from the old hole, so figuring it out shouldn’t be a problem. The reason I did this was because I couldn’t get enough cable to reach all the way forward to the connection up front. This got the extra inch I needed.
<O
Next run your ABS lines. They follow the IRS subframe to the front and go into the frame like the old ones did. No sweat. I lowered the lift and plugged them in….that was it.
<O
Next re-attach your Drive Shaft, If you don’t do this prior to the exhaust it might be a headache…so do it before.
<O
I would suggest indexing your DS now……..otherwise you will have a pretty big driveline vibration.

workmangc

Here is some info for you SN95 owners looking for something different.

I had originally thought that this was a Fox install, but it is a SN95.

virginiavenom

sorry man! sorry, I knew I had to do something that day.....you shoulda just called me!

96TennGT

Gary,

If I did the subframe bushing before install could I do the A-Arm bushings later without taking the whole IRS out?

Byron

workmangc

Byron,

Sorry for the late reply, I've been on vacation (sort of) out of town.

Anyway, yes you could do the A-arms after without much hassle. Your spring would be the biggest issue that I could see. However, without the A-arm bushings you will probably see some wheel hop.

Also, if you haven't ordered your IRS subframe bushings yet, call MM and get the ones from them that are 96-98 swap specific. Your stock LCA bolts are 12mm and so are the holes in the car subframe, The IRS bushings, and aftermarket ones as well are 14mm. If you don't put in bushings that are 12mm you will have BAD wheelhop. If you already have the aftermarket 14mm bushings then you will need to order the bolts, and drill out your stock holes to 14mm to accept them. I got mine from MM.

I PM'd you my cell # incase you need anything.

workmangc

Coming soon, Write up of an Max Motorsports Rear Coil over install for the IRS, (hint, This was sooooooo simple of an install)