My Fox FTBR IRS Build

IronSnake

Beers for the boys
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Some of you know what happened to me on the trade. Long story short, the brackets never showed up, the assembly was worn the F out, and the passenger wheel bearing was shot. But I'm a glass half full kind of guy, and not a damn thing in this world can't be rebuilt so.. here we go.

I set out to snatch the 8.8 out of the car for prep work.

IMG_0683.jpg


I purchased one of those harbor freight XT 1200lb ft impact and I have to say, it made the job a breeze. It is very well built. I removed the 8.8 for this behemoth.

IMG_0698.jpg


IRS SWAP! I'm very excited to embark on my first IRS build. Done tons of PHB and solid axle builds. So this is a new adventure for me. The unit is an 03. It has low mileage axles in it (look to be too) and the pumpkin has recently been rebuilt with a 3.73. He included his bilsteins and H&R's to go along with it.

IMG_0709.jpg


I got it home and started digging into it, and low and behold, found some issues. One, this thing is heavy as hell. Two, man these bushings were shot. Since I can't leave anything alone, I tore it down and did a thorough inspection.

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As you can see, the diff bushing is absolutely murdered. No wonder he hated this unit. The ironic part is he had new poly front diff bushings in it. But not in the rear. The rear one is only like 40 bucks on MM's website. Crazy people will let things get this bad. The whole back side looks to be cover in gear oil (old) from a previous diff explosion. So I set out to clean EVERYTHING. Wire brush, degrease, repeat.

IMG_0713.jpg


I cleaned my rear diff bracket up and got it ready to go.

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After copious amounts of beers, the dog and the fiance being out of the house, and the roomie being moved out, i was able to focus and stare at the subframe for a bit. Eventually I said F it and remove the subframe bushings.

IMG_0714.jpg


After all of that work, I started to structurally look at the IRS subframe. It was in good shape, but was beginning to show it's age. Luckily no broken tabs or bad stories, but the welds were all corroded and rusted. I put the die grinder to work with a wire wheel. After I coated all of the exposed surfaces with ford PM-13A anticorrosion rust preventative. It's almost like POR15, but a little runnier and satin.

IMG_0723.jpg
 

IronSnake

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The following week, I had a friend come over, clean, sand, prep, and paint the subframe for me. It's the same color as the engine bits. Cast Iron grey. At the same time, my FTBR kit showed up.

IMG_0746.jpg


It ended up being a hot day the following afternoon, so I threw some VHT header clear on it since it's resistant to Oil and Gas.

IMG_0752.jpg


I found a used LPW cover on Facebook Marketplace from an IRS part out. That arrived on Weds.

IMG_0734.jpg


I took to cleaning it up, and per some SVTp threads I knew ahead of time the logo gets in the way of the diff mount. If you look at the picture above, you'll notice a notch/groove/spot on the logo. It was hitting in the car this cover lived in previously.

IMG_0745.jpg


To demonstrate the normal issues and why the LPW needed to come off, I mocked the rear mount up.

IMG_0753.jpg


After this picture, I chamfered the corner of the bracket, and ground a little more off the cover. I'm up to about 3/16" between the bracket and cover. Perfect. I then assembled the Delrin rear diff mount

IMG_0755.jpg


Then test fit the cover assembly

IMG_0756.jpg


After all of that fun being over with, I decided to take the bushings out of the freezer and throw the subframe bushings in.

IMG_0759.jpg


I had to make a makeshift press out of a steering rack bolt to pull the sleeves in. They are TIGHT

The next day the Fiance went off to get her hair done for engagement photos. So I set to building the lower arms. I pressed the bushings out with my press the other day, and scotch brighted the holes down. I drilled and tapped for the grease fittings after setting their location, and then had to slightly press the bushings in. With the sleeve in, the thing is so smooth and clean that the sleeve is about to fall out. I had to zip tie them all in there until it's ready to go together.

IMG_0764.jpg


Afterwards, I opened up the diff to check it out. Supposedly rebuilt, low miles, 3.73 and 03/04 Carbon fiber T-lock

IMG_0765.jpg

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Success. Looks to be all there. Spins smooth and free. Had a bit of an issue getting the diff to "rock" and show backlash. Plus it's aluminum and I have a magnetic base Dial indicator so.. that doesn't work so hot. But eventually I got a max 12 thousands out of the measurement. Decided to say screw it and throw in there.

So from there, I cleaned the gasket surface really well, tapped all of the holes, and removed the 16lbs of grey RTV that they used when they rebuilt the diff. It was genuinely too much RTV and i'm surprised it didn't cause issues. Afterwards, I cleaned all of the bolts, prepped the cover, and stuck it together with copper RTV. The gluiest RTV that's yet to fail me.

IMG_0773.jpg


Last but not least, I was able to find a set of brackets from a fellow in Augusta. He was nice enough to hook me up with them, so I mocked those up.

IMG_0758.jpg


And that's where I'm at. The ol' lady demanded I spend more than 15 minutes with her that didn't include car stuff, so we hung out with the dogs and cleaned the house. I did get to clean the garage though (at her request) so that was productive.

Only minor setback is while I moved everything around, I noticed the passenger wheel bearing made some minor noise/had a bit of a wiggle. So looks like i'm replacing that. If it's not one thing, it's another.
 

Rudders331cobra

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The following week, I had a friend come over, clean, sand, prep, and paint the subframe for me. It's the same color as the engine bits. Cast Iron grey. At the same time, my FTBR kit showed up.

View attachment 1487366

It ended up being a hot day the following afternoon, so I threw some VHT header clear on it since it's resistant to Oil and Gas.

View attachment 1487367

I found a used LPW cover on Facebook Marketplace from an IRS part out. That arrived on Weds.

View attachment 1487368

I took to cleaning it up, and per some SVTp threads I knew ahead of time the logo gets in the way of the diff mount. If you look at the picture above, you'll notice a notch/groove/spot on the logo. It was hitting in the car this cover lived in previously.

View attachment 1487369

To demonstrate the normal issues and why the LPW needed to come off, I mocked the rear mount up.

View attachment 1487370

After this picture, I chamfered the corner of the bracket, and ground a little more off the cover. I'm up to about 3/16" between the bracket and cover. Perfect. I then assembled the Delrin rear diff mount

View attachment 1487371

Then test fit the cover assembly

View attachment 1487372

After all of that fun being over with, I decided to take the bushings out of the freezer and throw the subframe bushings in.

View attachment 1487373

I had to make a makeshift press out of a steering rack bolt to pull the sleeves in. They are TIGHT

The next day the Fiance went off to get her hair done for engagement photos. So I set to building the lower arms. I pressed the bushings out with my press the other day, and scotch brighted the holes down. I drilled and tapped for the grease fittings after setting their location, and then had to slightly press the bushings in. With the sleeve in, the thing is so smooth and clean that the sleeve is about to fall out. I had to zip tie them all in there until it's ready to go together.

View attachment 1487374

Afterwards, I opened up the diff to check it out. Supposedly rebuilt, low miles, 3.73 and 03/04 Carbon fiber T-lock

View attachment 1487375
View attachment 1487376

Success. Looks to be all there. Spins smooth and free. Had a bit of an issue getting the diff to "rock" and show backlash. Plus it's aluminum and I have a magnetic base Dial indicator so.. that doesn't work so hot. But eventually I got a max 12 thousands out of the measurement. Decided to say screw it and throw in there.

So from there, I cleaned the gasket surface really well, tapped all of the holes, and removed the 16lbs of grey RTV that they used when they rebuilt the diff. It was genuinely too much RTV and i'm surprised it didn't cause issues. Afterwards, I cleaned all of the bolts, prepped the cover, and stuck it together with copper RTV. The gluiest RTV that's yet to fail me.

View attachment 1487377

Last but not least, I was able to find a set of brackets from a fellow in Augusta. He was nice enough to hook me up with them, so I mocked those up.

View attachment 1487378

And that's where I'm at. The ol' lady demanded I spend more than 15 minutes with her that didn't include car stuff, so we hung out with the dogs and cleaned the house. I did get to clean the garage though (at her request) so that was productive.

Only minor setback is while I moved everything around, I noticed the passenger wheel bearing made some minor noise/had a bit of a wiggle. So looks like i'm replacing that. If it's not one thing, it's another.

Looking good man. Sorry timing did not work out.


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Rudders331cobra

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Thanks man. All good, I appreciate the offer either way. I'm sure you would've been much easier to deal with/more honest than the other guy. But live and learn I suppose!

Sucks. But I will be glued to this build man. I see you had some unforeseen issues


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Skitzerman

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Philadelphia Pa.
Great job on bringing that IRS back to life. I did the FTBR bushing job on my IRS about seven years ago, so I know what a pain in the ass that job can be. The IRS install in a Fox is a very cool hot rodding project. Good luck as you proceed.
 

Chrome98Cobra

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Nice work. I just installed the complete FTBR kit in mine a few weeks ago. They should've came from the factory like this.
1.jpg
 
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IronSnake

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Thanks everyone. I'm looking forward to seeing how it rides and drives. Once it gets moving and I get a couple side jobs/projects out of the way, I plan to do coil overs and fluff the rest of the car up.
 

MTBSully

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Awesome work. Sucks when i get home from work and immediately head into the garage for what i thought was going to be the rest of the night and then the old lady comes down and says "I thought we were hanging out tonight"

Keep up the good work man
 

Jefe

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AZ
Fun watching this progress but damn I don't miss doing this mod. Be glad you didn't have to remove the IRS from the car first! Took me almost a week to do mine and I literally sweated out 10lbs. The first test drive after made it all worth it though
 

IronSnake

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Yea i'm not looking forward to the solo install.

I plan to pickup a trans jack/four wheel jack from HF to help me out. I do a bunch of side work so it's easy to write it off as a "tool" expense. I just get to continue to use it lol
 

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