Looking for an IRS to 8.8 Live Axel swap

BlackenedSVT · Aug 8, 2004

Any of you GT guys ever swap out your live axel rear for an IRS?
How hard of a swap is this? I am getting a 99 Cobra and want to remove the IRS and swap it with a 99+ Live axel rear. I kind of want to drag my car, and the 'wheel-hop' thing has to go.

Any of you guys in NJ want to swap 'em?

Let me know if you guys know anything about this. Or perhaps, where i can buy a 8.8 Live Axel for a 99 Cobra. Thanks!

krly79 · Aug 9, 2004

there is a sticky at modularfords.com

postban said:

My main reason for doing the live axle swap was wheelhop. It is bad in the verts, apparently a lot more than the coupes. I contacted 3 local Mustang shops and all of them quoted me $5000 or more for the swap. They were about $2000 higher than it cost me to do the mod.
I have had the axle in for only a few days and have not been too hard on it yet. I plan several more "reinforcing mods" before I really try to test it. Those will be completing the last few parts needed for the swap (sway bar, pinion snubber), the Apten Cooling mod and a 26 spline input shaft from Liberty Gear along with T56 teardown/rebuild. I also plan on having Dyno Daves weld up the Torque Boxes for longevity.

Some of the parts I lucked into through contacts at work, in my car club or at the place that did the install, Dyno-Daves in Brownstown, Michigan. The ones I did not pay for have estimated prices, but also part numbers so you can find them. I have tried to find as many part numbers as possible. I have all the major ones, just a few bolts I am missing the info on. My total will not really match this list because of some of the parts I was just given by friends. The list contains many parts marked with **. This indicates FORD ONLY PART, you must acquire these parts from a Ford source or Dealer unless you have other connections. All the rest of the parts either have several possible options or are not critical to finishing the job, Dust Shields for instance. See the Vendors list below for contact info on every place I got parts from or their websites. Also remember when ordering parts from a Dealer to mention you are an SVTOA member, typical 15% discount. Also the MCT source pricing is only available to members of the Motor City Terminators Car Club. Join here and save--? http://www.motorcityterminators.org/

When sourcing your Live Axle Swap you can shop around for best price on every component, some components or go to a reliable local shop and have them do the leg work. Maybe a bit of each is best. I know I could have got the ring and pinion cheaper but it was easier quicker just to pay retail for it.

My total cost for every part minus swap labor was $2976.65

Parts List
1. 8.8 Ford Rear Axle housing, stripped (WG&A $400 including brake brkts)
2. 8.8 T/A Reinforced Cover with bolts/washers/gasket (WG&A $170)
3. Moser 31 spline axles with ABS adapters (WG&A $285)
4. 31 spline Eaton Posi unit with metal clutch plates (WG&A $380)
5. FRPP 3.73 Ring and Pinion (WG&A $195)
6. Timken Wheel Bearing (WG&A $20)
7. CK Wheel Seal (WG&A $12)
8. Timken Bearing Kit (WG&A $100)
9. Welding tubes, additional weld on brkts and assembly of rear unit (WG&A $150)
10. 4oz Mopar Friction Modifier and 3qts 75/140 Synthetic Gear oil (WG&A $25)
11. ABS Tone rings F4ZZ-2C189-A (quan 2) (MCT source $13.28ea)**
12. Cobra Pinion Flange E9TZ-4851-A (MCT source $23.80)**
13. RH Brake Bracket F4ZZ-2C100-B (MCT source $63.92)**
14. LH Brake Bracket F4ZZ-2C101-B (MCT source $62.84)**
15. RH ABS Sensor BRAB-138 or 3R3Z-2C190-CA (MCT source $35.64)**
16. LH ABS Sensor BRAB-137 or 3R3Z-2C190-BA (MCT source $28.22)**
17. GT ABS Sensor Bolt (quan 2) Estimate $4 (Supplied by friend gratis)
18. LH Exhaust hanger XR3Z-5260-AA Estimate $20** (Supplied by friend gratis)
19. RH Exhaust hanger 3R3Z-5C263-AA Estimate $20** (Supplied by friend gratis)
20. Exhaust Hanger Clip HN3(quan 4) Estimate $10** (Supplied by friend gratis)
21. Exhaust Hanger Bolt HS1 (quan 4)Estimate $10** (Supplied by friend gratis)
22. Shock Mount Bracket 18164 (quan 2) Estimate $20** (Supplied by friend gratis)
23. Shock Mount Bolt/Nut HB1 and HN1 (quan 2 ea) Estimate $10** (Supplied by friend gratis)
24. Strange Eng. 10-way Adj shock #S6004LM (quan 2) $65 ea (online from Strange)
25. Fox Body Mustang Springs CC835 (Downriver Spring Service $81.37)
26. Urethane Rear Spring isolators 2114-6101G (Ramchargers $18)
27. X2C UCA/LCA X2CBXR9904 (X2C ONLINE$162.40 shipped)
28. Differential-to-UCA bushing 1R3Z-5A638-BA (quan 2) (MCT source $8.17ea)**
29. Rear Upper Housing Bushing Set 29264049H (Ramchargers $22)
30. UCA Bolts HB1 or W704586-S426 (Quan 4) (Jack Demmer $4.36ea [15%SVTOA])
31. UCA Nuts HN1 or WS20214-S60 (Quan 4) (Jack Demmer $3.13ea [15%SVTOA])
32. LCA Bolts HB2 or W704939-S426 (Quan 4) (Jack Demmer $5.14ea [15%SVTOA])
33. LCA Nuts HN2 or WS20215-5427 (Quan 4) (Jack Demmer $4.25ea [15%SVTOA])
34. REAR DAMPNER KIT (Pinion Snubber) F8ZZ-4A263-AA $22.82
35. REAR SWAY BAR 23mm F6ZZ-5A772-BA (MCT source $87.15 )
36. SWAY BAR BOLT M10 N808928-S436 (quan 4) (MCT source $3.59ea )
37. SWAY BAR NUT & RETAINER N811481-S436 (quan 4) (MCT source $2.11ea)
38. DUST SHIELD F4ZZ-2C028-A (quan 2) (MCT source $7.81ea )
39. DUST SHIELD SCREW/WASHER N602726-S2 (quan8) (MCT source $3.27ea)
40. Fuel Filter (Napa #3595 $11.42)
41. 7mm Nylon push pins (Quan 6) (Supplied by friend gratis)
42. Borla Catback Exhaust (over-axle GT type) (Extreme Motorsports $449 shipped)

1. Our cars can use a Ford 8.8 from ?99 to the current year. Most earlier 8.8 assemblies are narrower by 3/4" per side. Some guys say you can use them for their ability to allow wider tires. I cannot confirm that so I suggest a ?99 or later housing. The new housing (stripped, empty) by itself is not available from a retail source, only available as a stock complete replacement axle assembly. You get to pay about $750 for it with 3.27 gears in it. It will have a 3.27 ring and pinion (discard), 28 spline stock axles (discard), 28 spline stock Traction-lok differential (discard), seal (non-reusable), Bearings (non-reusable) and sheet metal rear cover (discard).
The only pieces you need are the actual housing (cast/milled center piece) and the axle tubes with ends on them. You can go to a salvage yard to find one but will need to inspect it carefully. The tubes can sustain bends and might need straightening, this is common. A good axle shop can do the straightening as even my new unused axle tubes needed a few spots worked on. The ends on the axle tubes can be of many varieties too. They are where the brake brackets attach to the axle. Some people selecting to use different brakes choose different ends, such as FORD 9? ends. Not really sure on why, most always drag racing related reasons, slick clearance and such.
My housing was acquired from Bill Amsdill of Warren Gear and Axle. He has a Ford source that got him the housing and the MACH1 brake brackets for $400. Considering the brackets run like $80ea retail that is a decent deal. I met Bill Amsdill at the Autorama car show and he mentioned he could do the job for a low price and had lots of experience. I took a chance and it paid off. I recommend them highly, real nice folks to deal with.

2. The T/A cover is a very robust cast/milled aluminum piece with a special bearing loading setup. The two bolts on the rear center rib apply load to the two main axle bearings. This adds a good bit of strength to the whole center part of the assembly. WGA supplied me with the bolts, washers and the gasket for this cover.

3. Moser 31 spline axles are rated to be withstand 7000 lb/ft of torque, yes, seven thousand, straight from their webpage http://www.moserengineering.com The number may seem high but that is considering the multiplying factor of the wheel radius and the final gear ratio. They are good to maximum power the 8.8 housing itself can withstand which is 750-800 RWTQ. There are several options here including other vendors like Strange or FRPP. These axles must have ABS Tone Ring adapters pressed on inorder to keep your ABS functioning. Moser charges $20 per axle to do this. It makes it easy for your assembler to further press on your ABS Tone Rings.

4. The Eaton posi traction unit seems to be a very popluar choice among those upgrading differentials. It is preferred over the similar unit from Auburn Gear because of ease of rebuilding should a component fail. I also went with the metal clutch plates instead of carbon fiber ones at the urging of WGA. The carbon fiber supposedly wears out faster and the only downside of the metal ones is potential for more noise. That potential is reduced by adding Friction Modifier, which I did. There are many options here also, the Auburn unit is a bit cheaper, there is the Detroit Locker (loud clicking noise when one wheel slips) and also the spool (single piece unit permanently locking both axles together, very rough jerky motion in turns) for dedicated ¼ mile racers only.

5. I wanted a little more gear in the car so I went with 3.73 ring and pinion. There are guys using 3.90 and 4.10 but I did not want that much. WGA advised of noise problems with the 3.90, which I was considering briefly. I had heard the same complaint elsewhere but also was told it would be fine if setup right. I decided 3.73 was fine as I had had that in another car and liked it. It feels fine and is not too much gear at all for a S/C motor such as ours. Should be finishing the ¼ more towards the middle of 4th gear instead of right after the shift from 3rd.

6-7-8. These are all components recommended by WGA as high quality. They have been using them for years with good results.

9. Welding axle tubes to the cast iron housing is a popular reinforcing step when building up an axle for heavy-duty usage. It keeps them from moving (duh) or rotating. Stock 8.8 rears are not welded; the axle tubes are just pressed in. WGA also chased (added to) the welds on the brake brackets and tube ends for additional strength. WGA built up the whole assembly to spec and informed me the backlash was set to an ideal 0.008?. There are quite a few tricks involved in getting a trouble free rear setup. There is a part inside called a crush flange. There is no torque spec for it; you just keep tightening till the axle requires 20-in/lb torque to rotate. Could be 250 ft/lbs required, could be 450 or more. There are several spacers bearing and shims required to do it too. If you know what you are doing, have at it. If you are uncertain at all, better to have a guy with 25yrs experience to it-------WGA. Brad at Dyno-Daves also can build up an 8.8 for you, he mentioned he has done quite a few.

10. The Friction Modifiers purpose is to quiet the potential noise the metal clutch plates in the differential could cause. It would only be noticeable in tight turns but since it is easy to remedy I did. I chose to use Synthetic Differential fluid, the proper viscosity is 75/140. If you use non-synthetic 75/90 is correct.

11. The ABS tone rings on our IRS are those little gear-looking wheels on the inner side of the inner CV joint. It works by magnetic pulse. These are also called ?exciter rings? The space between the teeth causes magnetic pulses to be read by the ABS sensor and detect wheel lockup during braking. On the 8.8 Live Axle they are in an entirely different place, all the way out past the tube end and brake bracket. It still looks like a gear, just wider and larger than the IRS ABS tone ring. These need to be pressed on the axles before final assembly. Also you may need to use ABS Tone Ring adapters if the axles are not designed to be used with ABS Tone Rings. It is just a small flanged ring pressed on the axles near the stud flange.

12. In order to keep your Cobra?s Aluminum Drive shaft you will need to use a Cobra Pinion Flange, which is larger in diameter than the standard flange that comes on an 8.8. It is also a good idea to go ahead and buy a new Cobra flange instead of taking off the one from the IRS. They are pretty inexpensive and it makes it easier for your differential builder too.

13-14. These brake brackets are the same one used on the 97-98 Cobra and also the ?03-04 MACH1. They are considerably more expensive than listed above when bought retail. They need to be put on before the axles are installed. So if you are doing a swap with a GT owner you will need to pull the axles and install these if you wish to keep your Cobra brakes.

15-16. The GT ABS Sensors have a small round post instead of the flat rectangular tab ?exciter sensors? that are on the IRS ABS Sensors. They also use a smaller bolt to mount on the MACH1 brake brackets. They are about half the length of the IRS ABS Sensors too. In order to plug/unplug them you will need to get the upper liner out of the car trunk. They plug into their wiring harness right at the back topside of the rear wheelhouse on both sides. This is where Item #44, 7mm Nylon PushPins will come in handy. You will be removing about 5 of them to gain access and they usually break on removal.

17. A smaller screw size bolt is used for holding the GT ABS Sensors in place. Unable to find this number, luckily Brad had a couple of them in a drawer.

18-19-20-21. The Cobra catback is suspended from the IRS on our cars. You will need these brackets to properly suspend the catback, which must now go up and over the axle instead of under as the IRS exhaust does. They need special clips and bolts that fit to holes already in place under your car.

22-23. These were a bear, We ended up going to a salvage yard and getting them off of an ?88 Cougar right in the middle of the swap. They were not included on the rear housing from WGA. These mount the lower end of the shock to the shock bracket on the axle tube. The top of the shock mounts through the floor in the trunk.

24. I picked these shocks because of the adjustment range, performance and low cost. They also have a good reputation on the Mustang Boards.

25. I researched springs quite a bit. A few swap guys have complained about stock ?99-up GT springs as being even higher looking than our stock IRS. The GT springs are also very different spring rates too. Typical for GT is 200 lbs/in whereas our IRS springs are 470 (vert) and 600 (coupe). Don?t think you can swap IRS springs into a solid axle, way too stiff, wrong height and the bottom is not shaped properly (I was asked ?why not? in a recent email). The spring shop I went too stated these springs would make for a slight drop and work well with the rest of the live axle. They are stock springs for an 87-93 Mustang GT. Initially they provided a 3/8? drop and a good ride. Springs are supposed to settle a bit in the first few hundred miles so they may go down a little more.

26. There are isolators on your IRS springs, mainly to prevent squeaking. You also need them on a swap. I went to Ramchargers for these, probably many types available. They are basically just a urethane spacer between the spring and the car and the lower control arm.

27. These Upper and Lower control arms are good quality, robust design, come with firm bushings and also very cheap. They also preload the pinion angle to good street/strip friendly 2 degrees. They are much better than stock upper/lower control arms with their undesirable squishy rubber bushings for getting a good launch. You can go really crazy on control arms. I could have turned the $150 spent on these into almost $800 at the Maximum Motorsports site. The adjustable lowers are designed to raise the car to use larger diameter slicks. The adjustable uppers are used to increase the preload down-angle on the pinion (axle housing) Drag racers like about a 4-degree down-angle for best launches. Everybody makes UCA/LCA?s for Mustangs, Steeda, UPR, HPM, Metco? I?m sure there are many more, good luck choosing.

28. This is the bushing that goes on the Differential ?Ears? and mounts to the Upper Control Arm. It has a steel sleeve that you need to use along with Item #29. You remove the steel center sleeve and press out the rubber bushing. Then insert #29 and reinstall for a very solid relationship for the UCA.

29. There are a couple different durometer bushings you can use here. I went with these highest durometer ones to add stiffness for less deflection.

30-31-32-33. Factory bolts for factory type fit. These bolts are also galvanized for longer, less rusty life should you need to make changes under there. The nuts are also treated, have large attached flanges obviating washers and are the nylon locking type. You can choose to use regular hardware store type bolts here and save a good deal of money. They won?t be galvanized or certified for rear end use however.

34. The pinion snubber is a bumper that attaches via a bracket to three clip holes under your car. Another instance where you need the clips to attach to a panel and a bolt to go through that and snug it up. The pinion snubber uses the exact same clips and bolts as the Exhaust hangers.

35-36-37. I recommend using a Rear Sway bar, some guys don?t but I tried it and it feels too weird. The car jiggles long after going over a bump and does not recover well. Also cornering feels awkward. You can always take it off at the strip if you want the weight delete.

38-39. Brake shields are not essential but the IRS had them so I got them for the live axle also.

40. Change your Fuel Filter while you have the IRS out. You will never have easier access to it.

41. You might need these after plugging in your ABS sensors in the trunk. You have to remove a few pinned down trim pieces and these pushpins like to break.

42. I chose Borla for my exhaust for this swap. I drove 15000 miles with my Bassani?s on there, still like the sound fine, just time for a change. Extreme had MACH1 Stinger catbacks on sale for $449 shipped so I grabbed ?em. No regrets at all, a little louder, a little deeper and a bit more drone. Several compliments so far too.

Swap Steps
My swap was done by a mechanic named Brad at Dyno-Daves. It took a little over 6 hours but that included two hours of delay for parts runs, totally my fault. Brad is a very knowlegdeable young wrench with an excellent attitude. A lot of other talents too, TIG welding, Roll cages, Subframes, Auto-trans build up and lots more.

This is a general overview of the process as I saw it done. There may be some details omitted. You are responsible if you decide to take your car apart and can?t get it back together. Proceed with extreme caution; remember this is the Internet.

Many associated pictures of the components and the swap in progess are available here, http://www.imagestation.com/album/?id=4287212243
You will need to register (free) to view them.

1. Remove upper trunk trim liner to get access to top shock mounting nut and ABS connector.
2. Remove the shock nut and unplug the ABS sensor.
3. Jack car up, preferably with a lift, tough job on jackstands. All following instructions assume use of a lift.
4. Remove rear wheels
5. Remove bolts from brake caliper assembly, do not disassemble or detach the brake lines, suspend the entire assembly from wheelwell with wire or ziptie
6. Remove brake disc
7. Disconnect emergency brake cable
8. Remove emergency brake assembly
9. Remove driveshaft bolts from pinion flange and then remove driveshaft from transmission
10. Remove bolts from Rear ABS Sensors, pull sensors out.
11. Remove lower shock mount bolts, remove shocks from car.
12. Remove catback exhaust.
13. Support rear of IRS with tall screw-type jackstands and remove the rear IRS subframe bolts. Also loosen the nuts on the front subframe bolts, do not remove yet. This allows easier pivoting of the IRS in the next step.
14. Lower jackstand and allow IRS to pivot forward SLOWLY to get the springs out. Be careful they are very strong. You could also use a spring compressor to do this.
15. Pivot the IRS back up and just put the bolts back through the hole. Remove the nuts from the front IRS mounts.
16. Lower the car down to 2 feet off the ground and support the IRS on jackstands.
17. Remove the IRS bolts and then raise the car up separating it from the IRS. Move the IRS out of the way.
18. Lower car back down and install new shocks (need to tighten bolt from trunk)
19. Install new ABS Sensor through same hole as old one. Plug it in.
20. Raise the car back up and change the Fuel Filter if you are gonna do it.
21. Install Pinion snubber
22. Install Left and Right Exhaust hangers
23. Install the Upper Control Arms on the car.
24. Install the Lower Control Arms on the car.
25. Raise the 8.8 up into place, support it with tall jackstands and attach the upper control arms.
26. Put the isolators on the springs and then put the springs on the lower control arms.
27. Use a tall screw type jackstand to raise up the lower control arm (compressing the spring) until its bolt can be installed to the 8.8.
28. Install shock mount brackets and attach lower end of shock.
29. Install ABS Sensors on brake brackets
30. Install Emergency brake and Emergency cable both sides.
31. Install Brake discs
32. Install Brake Caliper assembly
33. Install Dust shields
34. Install Driveshaft
35. Install GT type up&over catback exhaust.
36. Install rear wheels

Vendors
Installer ~~~ Dyno Dave, Dave Roy, 17608 Telegraph, Brownstown MI 48180 734-229-1290

Axle housing assembly ~~~ Warren Gear & Axle, Bill Amsdill, 3513 E.10 Mile Rd, Warren MI 48091 http://www.nonamecarclub.com/warren_gear.htm
Shocks ~~~ Strange Engineering www.strangeengineering.net
Axles ~~~ Moser Engineering http://www.moserengineering.com/
Differential ~~~ Eaton Posi http://www.eatonposi.com/
Borla Exhaust ~~~ Extreme Motorsports http://www.xmsengineering.com/
Control Arms ~~~ X2C Motorsports http://www.x2cmotorsports.com
Springs ~~~ Downriver Spring http://www.downriverspring.com/
Differential Bushings ~~~ Ramchargers www.ramchargers.com
Ring and Pinion ~~~ Ford Racing Parts www.fordracingparts.com

thread located here ----> http://www.modularfords.com/forums/showthread.php?t=12000

01TrueBlueCobra · Aug 9, 2004

I want a solid Axle too. Anyone living in southern California with a GT or Mach 1 that wants IRS let me know.

mity2 · Aug 9, 2004

i like to get IRS...

BlackenedSVT · Aug 9, 2004

Mity2, where yo located? I'll swap an IRS for your live axel

And Krly79, thanks for the post!!! HUGE help!

krly79 · Aug 9, 2004

any time.

masicinap · Nov 4, 2006

i want irs

i got a 2000 gt, i want irs.

BennyBlown2v · Nov 4, 2006

It's not that hard, I've done it a good 7-8 times. Just take your time and make sure you have a good two days if you wanna do two cars (unless you have a shop doing the work, but thats just a waste of money imo).

san~man · Nov 4, 2006

Post wanted items in classifieds please.

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Looking for an IRS to 8.8 Live Axel swap

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krly79 Member

01TrueBlueCobra New Member

mity2 I like Pro3 and all I got was this crappy CT.

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