The IRS Swap has begun...Almost Finished!!!

[86lx]

I have finally decided to get started on swapping a 03 Cobra IRS assembly into my 86 LX (now known as Frankenstang). I just finished getting the old rear out and have begun to plan on what needs to be fabbed/modified. It looks like a very straight forward swap. I need to remove the brackets the the rubber axle snubbers attach to, mount the rear IRS mounting brackets, and do some brake line fabrication. But, other than that it's mostly a bolt-in deal. I'm also contemplating removing the upper control arm to body mounts. I don't think they will be in the way, but they also aren't doing anything, and would make for a cleaner install if they were gone. Any thoughts? Most of the swap will follow along with what the Mouthbreather Motorsort guys did . http://www.mouthbreather.net/IRSSWAP.html
But, I may come up with a different way of mounting those rear brackets. I'll start taking some pictures of the whole process in case anyone else is interested in doing the same swap. Feel free to post your thoughts on this. However, I don't want this to become a discussion on the pro/cons of the IRS, or an IRS vs. live axle debate. I'm committed to doing it, and think if I can pull it off with a very clean install it will be a very unique and impressive setup, along with the other mods I have planned for the car (see my post in the online car show section). More to Come...

[Evil86lx]

Cool. Take lot's of picture's cause I want to do this to my SVO.

kyle

[eric5oh]

The best way to bolt those brackets is not to use a long bolt and sandwich the frame rail. Use a hole saw in the trunk right above the frame rail and tack weld a nut inside of it. Then either use a plastic rubber plug, or weld the hole closed. There are a few people in my area that have done it and I have checked them out personally. I actually have the complete 03 IRS unit (new take out from racer Ken Moss's car) and I've decided not to do it. My car is a little too rare to hack up.

[86lx]

Thanks for the advice, I'll give it some thought. I've also thought about making a plate to weld the 2 long bolt going down through the frame rails onto, plus welding sleeves into the holes through the frame rails so there's no chance of crushing them. My orignial plan was to simply weld the brackets in place, but, after looking at it last night I think bolting them in will be the stronger setup.

Thanks again, I don't think I'd be hacking up an ASC/Mclaren either.

[eric5oh]

Don't forget to support the other side of the bracket with steel plates. Steeda has them for $30 or something. Double check for that 12 or 14mm bolt issue, and you'l definitely want the poly/delrin bushings all around.

[86lx]

what 12 or 14 mm bolt issue are you referring to? I haven't heard anything about that. As far as the bussings and other aftermarket goodies go, I'll wait till I get it installed. It's going to be a long time before this car sees any serious use. Eric, you seem do have done alot of research on this swap, please share your knowledge. Anyone have any thoughts on the removal of my stock upper control arm brackets?

[eric5oh]

Personally I wouldn't remove the brackets. you may decide you hate the its and want to go back. I may be wrong, but I think the early 2003 cobra irs units were built using 12mm attaching hardware in a 14mm hole. That created a bunch of slop as you can imagine, only worsening the irs's wheelhop issue. I think it was the bolt that holds the irs subframe to the bracket where the quad shocks go. I researched it for awhile, as a matter of fact, it is still loosely bolted into the car. (I didn't go as far as drilling and cutting new holes, I couldn't bring myself to do it.) It is too wide for me. 3" or so overall. The wheels I want to use stick out too far, even with the Capri's bulging fenders. A local guy here did it on his 91 GT. He used the 17" split 5 spoke wheels found on the 96-98 Gt, and the wheels sit flush with the wheelwell lip.

[86lx]

Most of my hardware I will be buying new, so I'll make sure I get the right size. The wheels I have now are off a 99 GT. With the stock rear there seemed to be at leat an inch and a half of room, but I'll see after I get everything in the car. I think the exhaust is going to be my biggest challenge. It's a V-6 car, and I have a set of manifolds and Y pipe lying around from a 99 3.8 stang that I want to try. I might use spintech's side exit system which would solve all my issues. I'm still undecided about the UCA brackets, I doubt I'll ever change it back, but then again, i doubt anyone would ever notice. Today I'll take some pics of my starting point (rear out of the car). Stay tuned...

[795.0pacecar]

If your going to change the bushings at all, your better off doing it while the unit is out of the car first. My dad put an 03 IRS in his mach 1 and even with the irs out of the car the bushings weren't easy to install.

[Zap's 85 GT]

Exhausts for the IRS Cobras run under the rear instead of over it. You could look for a used cobra cat back and see where to go from there. You see them for sale all the time on e-bay for not too much money.

[eric5oh]

It's a shame you are not in the midwest. I have a stock catback, driveshaft, bushings, etc. Oh, and BTW, I have heard conflicting reports, but I'm pretty sure you need the 93 Cobra Ebrake cables. You can get them new from summit for $35 each.

[86lx]

My folks are in MI, but that still doesn't help with the shipping costs any. I actually had the IRS shipped from NC. The seller was able to get a good deal on shipping, and even knocked some off his base price for me, so I got a scraming deal. I knew about the e-brake cables, i also need to upgrade my master cylinder for the rear discs. No pictures got taken today, but I'm sure you all know what a mustang looks like minus the rear end. I'll snap some this week and get them into my photo album on Yahoo! I think the side exit ehaust might be the ticket for me. Spintech makes a dual side exit system for the newer sixes, so as long as i can make those manifolds and Y-pipe work it will be a bolt in job. I just can't wait to get this project really going.

[86lx]

OK, I finally got off my butt tonight and pulled my gas tank. After that I decided to trial fit the IRS. It was very easy to position, thanks to the dolly I made to move it around with. Basically I just slid it underneath the car, and began jacking it up...lining it up as I went. Once I got the front mounts in place I bolted the left rear mounting bracket (I need to buy the bracket for the RR) to the IRS cradle and jacked it up until the bracket made contact with the frame rail. It seems to fit without any major clearance issues. There will be some minor sheet metal massaging around the shock area, and the axle snubber brackets have to come off, but that's about it. I may also have to relocate my fuel filter, but we'll see when I try to put the tank back in. I think my stock driveshaft may also fit fine, which is a very good thing. I took a couple pics of tonights work and posted them in my Yahoo! album here...

http://briefcase.yahoo.com/snovicki@sbcglobal.net

Hopefully I'll be getting more accompllished in the next couple weeks...Stay Tuned!

[v8only]

Wow, that's just about the neatest damn thing I've seen in a while. Nice pictures, and nice work. Can't wait to see your final opinions. I've never even been in an irs mustang before, let alone a fox irs setup. Good work.

[eric5oh]

Let me know if you run into a snag getting parts. I have some left after I sold my 03 IRS setup.

[86lx]

Thanks Jeremy and Eric. I really want to do something different with this car, and I think this may be the ticket.

Eric, What parts do you have available?

[eric5oh]

Just about everything. The IRS (in my opinion) is too wide for the car. I don't want to run custom wheels. It is almost 3 inches wider than the stock 8.8 it is replacing.

[86lx]

I just did a test fit of one of the tires. I'm using 99 GT wheels with 245/45-17 tires and they seemed to fit ok. I didn't have the brake rotor in place, and the sidewall of the tire seemed to fall just short of the fender lip. Add a quarter inch or so for the rotor, and everything should be ok. I may have to roll the fender lip after everything is said and done, but that's no big deal. Of course any plans I have of going to wider rubber is pretty much gone.

[86lx]

The bracket I've been waiting for for the right side finally arrived yesterday. I knew it was coming, so I jacked the IRS into place and bolted the front mounts in. As soon as the bracket arrived I mounted it to the subframe and began to look for interference points that would have to be worked on for a good fit. The first spot I noticed was the sheetmetal bracing on the backside of the shock tower. A little massging with a ball-peen hammer and it moved right out of the way. The next point of interference was the bottom lip of the inside of the wheelwell on the back side. I trimmed this about 5/16" and the bracket cleared with plenty of room to spare. The only other place I see right now is the sheetmetal "bracket" that holds the front right mount for the fuel tank, as well as the mount for the fuel filter. I'm hoping that some more hammer work will persuade it to get out of my way. I still need to buy a spotweld cutter to remove the axle tube snubber bracets. Once those are out of the way I'll get everything up in place and start locating the brake lines and the other small details. Once I get eveything laid out I'll drill the holes for the frame barckets and get everything mounted permanently. Stay tuned for more.

I snapped a couple pics today, you can see them here:
http://briefcase.yahoo.com/snovicki@sbcglobal.net

[86lx]

Well, I decided to do a little work on the car today. I got the IRS subframe brackets bolted in place (just 1 bolt each for now), and mounted the brake rotors and wheels and tires. The first thing I noticed was the width of the track. I will definitely have to roll the fender lips when all is said and done. It looks good though, kinda wish the front track was wider to match. Now it's time to plan the location for the 3 holes I need to drill per side and lay out the brake lines. It's coming together (as quickly as time and funds will allow). Hopefully I can make it driveable soon. I took some pictures of how it sits today. Take a look at them here:
http://briefcase.yahoo.com/snovicki@sbcglobal.net

[86lx]

From 21 Feb.

I figured I might as well update you all on my progress.

Everything is basically done. The brakes are plumbed, everything is bolted up. I just need to replace the bolts I used to mount the rear subframe brackets (snapped 1 while torquing it - buy grade 8 bolts). I have an 85 town car master cylinder sitting on the bench, just ordered the plug for my proportioning valve. I need to pick up some fuel line clips from the dealer today, so I can have the gas tank back in tonight. Hopefully there's room for me to just put a turndown on the muffler, don't have money for the exhaust right now. The only thing I'm still unclear on is what parking brake cables to use. If anyones' got any ideas, I'm listening. you can see the pics here http://photos.yahoo.com/snovicki@sbcglobal.net

[86lx]

I'm so close to being done I can taste it. I picked up a Wilwood adjustable proportioning valve today. Also had to get a 1/4"-3/16" flare nut for the rear(front brake)port on the Town Car master cylinder. I couldn't find an adapter, so I just cut the old(too big)flare nut off, put the new one on and re-flared the line. I bled the brakes, but the rear lines are leaking from the crush washers (re-used the old ones). I'll pick up some new ones tomorrow morning and hopefully find a muffler that will fit. That will just about do it. I still haven't changed the e-brake cables...no big deal, it's an automatic. Even if I can't get the exhaust done tomorrow I'll give it a test drive after the brakes are done. Can't wait! I'll get some pics of the details before the first test drive, and of course some exterior shots after I wash the dust off!

[jeffascmclaren]

That is awesome! I have contemplated this swap as well. I was most interested in some better ride characteristics.

[Zap's 85 GT]

I made my own proportioning valve block off plug by welding up the hole in the original one after removing the rubber thingie.