The "Ultimate" IRS Swap for S30s

[wfritts911]

Alright I'll come clean. I have been working on what I will call the best IRS swap for S30s. I have been running my setup for ~9 months now without a single issue. This eliminates every weak link that I know of, gives plenty of differential/gear options, uses minimal custom parts, and will hold a LOT of power. So on to the details, starting from the inside going out towards the wheel:

 

• 8.8 IRS differential from 02-05 Explorer/Mountaineer. Woooo! Gear and differential options! 8.8 parts are plentiful and cheap.
• Custom stub shaft I produce that allows a porsche 930 CV Joint to bolt on. Driveshaft Shop also sells the same shaft at ~250 a piece. 31 Spline.
• Porsche 930 CV Joint
• Porsche 930 Axle. Chromoly off the shelf axles run 220 a pair!
• 97-03ish F150 Front CV axle OUTER CV Joint. Heres the secret, this CV joint uses the same splines as the porsche 930 axle. It splines into the hub with a 33 spline shaft. This thing is beefy. Definitely no stub shaft failures happening here. Parts stores stock the axles.
• 2000ish Dodge Intrepid Front Hub. Here is the even bigger secret. This hub uses the same 33 splines as the F150 front CV axle. Has a 5x4.5 bolt pattern(Easily redrilled to 4x4.5 for those looking to stay with stock 4 lug). Parts stores stock these for cheap
• Custom Strut tower that the Intrepid hub bolts to
• Wilwood 4 piston calipers, 2 piece rotors. More budget friendly brake setup is in the works, but this is the current setup

Now let me go ahead and address the "Man this guy is crazy, that is the most frankenstein setup ever." thought that is in your head. I won't lie, reading of the list sounds frankenstein. Dodge Hubs, F150 outer CV, explorer diff, (My setup uses Honda S2000 rear brakes and makes it worse), etc etc. Yes there are a lot of different parts going on, but they are stocked at parts stores, they are cheap, and they are strong.

 

The only driveline part that is breakable is the 31 spline to 930 CV adapter. I take the stock stub axle and weld on a flange that the 930 CV bolts to. I don't foresee these being an issue, but if they are, the DSS ones are an option, they are just expensive. If the porsche 930 stuff becomes a weak link, they sell 300M CV Joints and axle bars that will definitely not be the weak link. Every other part that is in harms way is an off the shelf part, 930 stuff is very common in the buggy world.

 

Kits will be available soon(Hope its ok to say that here). I will post in the vendor section with prices hopefully within a couple weeks. The custom parts include:

• Front Differential Mount.
• Rear Differential Mount. Billet aluminum, similar to what AZC sells.
• Upright/Dogbone piece(One piece unit connecting the 2 dropdowns to the rear LCA mount). Needed to clear differential mounting points
• 8.8 to 930 CV Adapter(Requires sourcing explorer rear CV Axles and sending me the stubs, or I can source them for you)
• Custom strut tower with bolt on strut tube. Similar to the TTT setup they sell for the R230 swap.
• Small axle spacer(Splines on F150 axle are longer than the Intrepid Hubs)
• The wilwood rotor hat needs the inside bore turned slightly larger to fit the intrepid hub. Currently working on a better solution for this, but its an easy fix.
• Driveshaft(Not provided by me)

Those are the only custom parts you need. All the coil over parts are off the shelf, off the shelf brakes, off the shelf axle parts, etc. You would need to source an IRS differential from an explorer and the rear cv axles from the same vehicle.

 

I will try to get some pictures posted later, sitting in class right now. Texis300 will be recieving the first set hopefully within a week(Sorry its taking so long bud). He will be making close to 700 wheel I believe and will be putting this setup through some stress for sure. I only make a wee little 350rwhp, so I'm not a good test of this setups capabilities. I don't see Texis300 breaking anything, but thats not say he wont. I will make modification to the setup if he finds a weak link

 

Also, for those thinking they don't need the extra strength of the 8.8 differential. This setup will work the same way with the R200 and a bolt on 930 adapter. That will make the kit cheaper(No differential mounts). It will eliminate every weak link from the axles out, making the new weak link the differential or the differential stub shaft. I know SunnyZ was breaking the Z31 axle stubs, but maybe the stock R200 pieces are stronger? I can't remember if I've ever seen anyone break the stock differential stub shaft. Going with this setup will make the kit very affordable(Not that it isn't with the 8.8, but less custom parts makes it cheaper obviously)

 

Now I will open the floor to questions, comments, etc. Hope I didn't bore anyone with the book I just wrote

 

-Will

[wfritts911]

Here is a parts list, for some reason it wouldn't let me upload an excel file so yal get a screenshot instead. This is pretty accurate, but a couple part numbers have changed I think

 

-Will

Edited October 15, 2014 by wfritts911

[seattlejester]

Seems interesting. I'm not following the custom strut tower portion though. Do you mean a custom strut tower top?

 

So basically you are using the front hubs from the intrepid (which is front wheel drive thus the drive wheels), to the ford f150 cv to the porsche 930 axle to the porsche 930 cv to the custom 8.8 input stub to the 8.8 differential.

 

Any pictures? Would be interesting to see how it lines up/sits.

[socorob]

What kind of driveline angles are you getting with that setup?

[texis30O]

Get off the computer and get where you need to be!!!! I can "road test" a computer screen!!! lol.... the real deal!!

I am happy to say that Will has been plotting this out for over a year.  I think we have eliminated the weak links.  I just now  need to beat on it....I am anticipating putting a 315-335 rear tire on the car so we will see how this handles......

Edited April 15, 2014 by texis30O

[geno51]

I'm in!! Please keep me up to date. I will be making 750+ ls1 twin turbo. Keep me in the loop as much as you can

 

Thanks for this

[Dat260]

Sounds heavy duty and not expensive.

Edited April 15, 2014 by Dat260

[wfritts911]

^ Dat260, that was the only requirement for this setup. Strong as hell, and not expensive.

 

SeatleJester, The custom strut tower is similar to the TechnoToyTuning strut tower they sell for the R230 swap. Its is a completely fabricated strut that the Intrepid hub bolts too. The strut tube is fabricated as well and then bolts on and houses a stock style strut insert.

 

If by driveline angles you mean the cv axles, they are good. Then again the 930 CV's have no problem running at 20+ degrees and the F150 outer can do 40+.

 

School, work, this project, and life have me crazy busy lately. I got the thread mill to thread the end of the strut tubes in yesterday, so will hopefully get the complete strut tower coil overs and all assembled tomorrow probably, and will post pictures. Won't get the aluminum in for the rear mustache bar til thursday or so probably, so I will try and post pictures of the diff mounted in the car this weekend.

 

Sean, I will hopefully be mailing stuff off monday if everything goes swell, its so close. By the way, I'm extremely jealous of these Wilwoods and Koni's, stuff is nice!

 

-Will

[RebekahsZ]

Need clarification.  Which component goes into the differential as an output stub or side-axle flange?  I want to google a picture of that part.  Pics of your prototype as soon as  you have time (and don't flunk out of school).

[texis30O]

I picked up my diff from the yard today.  I am gonna look at lockers and lsd units over the next few days to wrap up things on my end ( I was told that the 8.8 does not come with a lsd and 3.55 ratio) I am looking forward to beating the hell out of this car and humiliating a lot of guys around here driving in their midlife crisis cars!!

Thank you again for all of your hard work! As always let me know what you need from me. 

[Domzs]

Great info .

[RebekahsZ]

My Z is my midlife crisis car! It used to be my young and rebellious car. Someday it will be my old-timey car.

[SUNNY Z]

I picked up my diff from the yard today.  I am gonna look at lockers and lsd units over the next few days to wrap up things on my end ( I was told that the 8.8 does not come with a lsd and 3.55 ratio) I am looking forward to beating the hell out of this car and humiliating a lot of guys around here driving in their midlife crisis cars!!

Thank you again for all of your hard work! As always let me know what you need from me. 

All the 03-04 cobra diffs were 31 spline, 3.55 gear, and a locker. The ford Trac-loc differentials are pretty tough, and cheap.

[texis30O]

The midlife crisis cars around here are store bought R34s, lambos, P-cars, and a few Ferraris....... None of which are modded.

But I digress......

@ Sunny, thanks for the heads up.  The Cobra diffs would not work for this application.  I will most likely build up this unit as it should be cheaper that way.

[RebekahsZ]

Will, didn't you say that your kit uses 33-spline inner stub axles?

[socorob]

Just for a little info. There is an explorer parked right next to my Z. My 6 bolt Q45 axle looks to be about 1.25 and the explorer is 1.430. That's the best I could get with a caliper under there. Almost 1/4" difference.

[socorob]

And here is the explorer service tag in case anyone wants to go a googlin some specs.

[JMortensen]

I think by "strut top" he means suspension upright, the part that the hub and strut will bolt to. Sounds beefy.

[wfritts911]

Not sure where I said "strut top" at, but I believe Jon has it correct. When I refer to strut tower, I am talking about the whole assembly that the hub and strut will bolt to. The LCA will bolt to the strut tower. The dodge intrepid hub, which is a standard bolt on hub like many newer cars, will bolt to the strut tower. A bolt on strut tube which houses the insert will bolt to the strut tower/backing plate. I have attached a picture of the fabricated strut tower with the strut tube bolted to it. Please excuse the awful picture and rusty metal. The large hole in the middle is where the intrepid hub sits. The to bolt holes on the left side hold the Wilwood 4 piston caliper. The strut tube is bolted on in this photo. For future discussions, I will refer to this whole assembly as the strut tower. This assembly without the strut tube bolted to it I will call the backing plate. And the strut tube houses the strut insert(Koni single adjustables in this case).

 

These parts along with the stub axles that spline into the diff will be getting welded up tomorrow, the rear mustache bar will be on the CNC tomorrow as well, along with hopefully finishing up the strut tubes. Hopefully I will be able to cut a final front diff mount on the water jet Friday and get it finish welded as well. Then I will bolt everything up and take pictures of the final products on and off the car, this set will be getting power coated by the owner so it will all be bare metal, but future pieces will all be coated.

 

I will be gone from tuesday til monday of next week for an SAE Mini Baja race in El Paso, so no work will get done during that time. But hopefully by the time I come back Texis300 will have recieved the parts and had time to put them on his car and post up on here about how nothing fits and its the worst setup around hehehe. But seriously, once I get the ok from him that everything works on his car as well, then I will begin ordering material and start building 10 sets.

 

The only tricky part to this setup is the F150 CV Axles you get from the parts store, the axle shaft is attached to the outer CV joint by a circlip, which is on the end of the axle. This clip compresses through the splined "star" and uncompresses on the other side. My sources said that you can just pound the axle out and the clip will pop through. I spent quite some time trying that before cutting the axle bar off right outside the cv joint, so the cv could be rotated far enough so the balls would fall out. Once I got the star and small axle piece out, I hammered on the axle from the back side and managed to get it through, but it took a BFH. I've got another set of axles sitting on the floor that I will be assembling for Texis, and maybe these will work easier, but mine would not pop out to save my life. I will be assembling Texis's axles for him, and may or may not do that for other setups.

 

More photos will be coming this weekend.

 

-Will

[wfritts911]

Keith, the 8.8 uses a 31 spline inner stub axle. Cobra guys put a lot of power through these things. The Intrepid hub and the F150 outer CV are 33 spline. Sorry for the confusion. I haven't looked too in depth, but I don't recall ever seeing a broken 31 spline 8.8 stub, maybe SunnyZ can chime in on that?

 

-Will