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Discussion Starter #1
All, I'm finally going to take the plunge and put a good rear end into my car.
I'm going to use an independent 9" as sold by the drive shaft shop and use an extremely high quality fabricator that has done lots of work for and with them.

Question
would anyone be interested in doing the same ?
Either way we will likely make drawings and such so that the fabricator can make more of the parts, but he and I wanted to get an idea of how much work to put into the replicability and "bolt in" portion since it will take more time and effort.

The parts from the drive shaft shop are high quality and therefore pricey but for the most part we get what we pay for so .....

Just want an idea of how much interest there may be

Thanks

Sevan
 

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Mike did the 8.8 and I'm working on the same. I doubt you'll make it "bolt in" The problem is you have to cut the factory diff cradle off. The other challenge is the larger yoke doesn't fit thru the opening in the crossmember.

I think the 8.8 is a better solution than the 9 for a mk2. It's far cheaper. If you don't change the outer stubs you'll just break those anyways next. Btw if you need a mk2 to 930 cv adapter I already have on designed.
 

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Discussion Starter #4 (Edited)
Drive Shaft Shop Ford 9" Independent rear Bolt in Kit for MK2

Thanks for the info on the 8.8 and the adaptor. Yes in order to make it bolt in a new tubular rear subframe is likely part of the solution / equation. I was originally considering the 8.8 , but for various reasons will likely be sticking with the 9" . I have a TH-350 transmission currently and as you say the hole for the drive shaft is very small, I believe there is around 1/8" / 3mm of gap between the adaptor from the large yoke drive shaft to the stock pinion flange.
There will definitely be upgraded parts all the way out to the rims, i'm hoping to keep the stock arms, but there's a chance that while making a new rear subframe we will also make new arms and have everything from the 9" to the rims upgraded.
Haven't been able to dyno the car as yet but it runs quite well.
Both videos below were while still only running / tuned for 13psi of boost

https://youtu.be/GAW-XoeRpbA

https://youtu.be/w61AwtcTQos


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Discussion Starter #5
SilverMk2 are there any pictures or anything of Mike's setup on here?


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I might have a ford 9" to sell... Been holding on to it thinking i might use it and never did. It looks a little rough, but I'll get pic later tonight. I'm in Kennesaw, GA
 

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Discussion Starter #7
I might have a ford 9" to sell... Been holding on to it thinking i might use it and never did. It looks a little rough, but I'll get pic later tonight. I'm in Kennesaw, GA
9" independent?
thanks !!


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Whistles
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Thanks for the info on the 8.8 and the adaptor. Yes in order to make it bolt in a new tubular rear subframe is likely part of the solution / equation. I was originally considering the 8.8 , but for various reasons will likely be sticking with the 9" . I have a TH-350 transmission currently and as you say the hole for the drive shaft is very small, I believe there is around 1/8" / 3mm of gap between the adaptor from the large yoke drive shaft to the stock pinion flange.
There will definitely be upgraded parts all the way out to the rims, i'm hoping to keep the stock arms, but there's a chance that while making a new rear subframe we will also make new arms and have everything from the 9" to the rims upgraded.
Haven't been able to dyno the car as yet but it runs quite well.
Both videos below were while still only running / tuned for 13psi of boost

https://youtu.be/GAW-XoeRpbA

https://youtu.be/w61AwtcTQos


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Looks like you beat the mustang. Nice.

I'm interested in how all this goes together. Eventually, I see myself having to go this direction.
 

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I have done the 8.8 IRS in my car with new 3.73 Ford Motorsport gears and a used Mach 1 Trac-Loc LSD center, and it has been amazing for me. As Aaron said, there is no real advantage to going to a 9" center unless you have a serious need for it. The form factor is difficulty large with the 9", aftermarket independent housings for 9" centers are expensive and bulky, and the entire assembly almost always tends to be VERY heavy. The aluminum case'd 8.8 came in a pleathora of Ford, Mercury and Lincoln cars, many of which are old enough to be piled up in junk yards ready for you to grab for cheap. There is a huge selection and well priced aftermarket centers for 8.8 assemblies, LSD and lockers from a huge variety of manufactures. Unfortunately Ford Motorsport discontinued selling brand new aluminum housings some time ago, but there are plenty of used ones out there to grab.

Again, as Aaron said, the biggest issue people aren't addressing with doing any kind of diff swap are the outboard stub ends and bearings on the trailing arms. They are one of the weakest links on the entire IRS assembly, so there is no point in spending money and time on the center if they also aren't addressed at the same time. Best case scenario in my opinion would be to use 930 CV stub ends (31 spline) on the diff side (make sure you are using a 31 spline center LSD of some type), a custom 4130/4140 heat treated chromoly outer stub end to adapt a 930 CV joint, and have the Driveshaft Shop or anyone else make the intermediary splined shaft to connect the 930 CV's. If I could do it over again I would spend more money and go that route to make a nice 700 ft/lb bulletproof axle setup, but my C5 corvette outer bearing and stub end setup has been working great for me at a measly 400 HP ft/lbs with my turbo V8.

I am willing to give anyone my center section CAD files for how my diff is mounted and planted if they need it, but I don't want to release the fabricated trailing arm files as they need some modifications to be "perfect" and I don't want to send them out the way they are.

I have been talking with some serious power members about just making a proper SLA IRS system as bolt on as possible for these cars, now that we have a 3D scanner and tube laser cutting system here at work. I would need a clean shell to scan as a baseline to start with, and have no idea when I would have time to tackle the project.

-Mike
-Mike
 

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Discussion Starter #11
I have done the 8.8 IRS in my car with new 3.73 Ford Motorsport gears and a used Mach 1 Trac-Loc LSD center, and it has been amazing for me. As Aaron said, there is no real advantage to going to a 9" center unless you have a serious need for it. The form factor is difficulty large with the 9", aftermarket independent housings for 9" centers are expensive and bulky, and the entire assembly almost always tends to be VERY heavy. The aluminum case'd 8.8 came in a pleathora of Ford, Mercury and Lincoln cars, many of which are old enough to be piled up in junk yards ready for you to grab for cheap. There is a huge selection and well priced aftermarket centers for 8.8 assemblies, LSD and lockers from a huge variety of manufactures. Unfortunately Ford Motorsport discontinued selling brand new aluminum housings some time ago, but there are plenty of used ones out there to grab.

Again, as Aaron said, the biggest issue people aren't addressing with doing any kind of diff swap are the outboard stub ends and bearings on the trailing arms. They are one of the weakest links on the entire IRS assembly, so there is no point in spending money and time on the center if they also aren't addressed at the same time. Best case scenario in my opinion would be to use 930 CV stub ends (31 spline) on the diff side (make sure you are using a 31 spline center LSD of some type), a custom 4130/4140 heat treated chromoly outer stub end to adapt a 930 CV joint, and have the Driveshaft Shop or anyone else make the intermediary splined shaft to connect the 930 CV's. If I could do it over again I would spend more money and go that route to make a nice 700 ft/lb bulletproof axle setup, but my C5 corvette outer bearing and stub end setup has been working great for me at a measly 400 HP ft/lbs with my turbo V8.

I am willing to give anyone my center section CAD files for how my diff is mounted and planted if they need it, but I don't want to release the fabricated trailing arm files as they need some modifications to be "perfect" and I don't want to send them out the way they are.

I have been talking with some serious power members about just making a proper SLA IRS system as bolt on as possible for these cars, now that we have a 3D scanner and tube laser cutting system here at work. I would need a clean shell to scan as a baseline to start with, and have no idea when I would have time to tackle the project.

-Mike
-Mike
Hello Mike, interesting indeed!
What CAD system do you use? I'd love to see some Step files or UG NX if that happens to be your system. I will talk to the fabricator and see what he thinks about doing it 8.8, your logic makes sense, only thing is around here aluminum 9" carriers are a dime a dozen, but having something to compare to would be great.
Where are you located? i'm in the Charlotte NC area


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+1 for the bolt on or adapted complete rear IRS from some other car with a proper multilink or double wishbone setup.

While you guys are right that just upgrading the diff without doing the outer hubs too is pointless, I personally feel putting any serious money into re-engineering a semi trailing arm setup like this falls into the same category. I am personally upgrading my LSD and doing the camber mod with relocated inner mounts to address the camber and binding issues and this improves the shitty toe changes this rear end gets under compression. My power goals are tame enough that this should be sufficient, but if I get more extreme on a different chassis, the whole IRS is going out the door and I'd encourage everyone else to do the same.
 

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Whistles
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I've been trying to find a solution to the outer hubs, too. It's all that is holding me back.

Even the bearings in the rear hubs are basically gone when they are gone. Toyota doesn't make all the parts anymore.

I agree, that going solid rear axle is probably going to be the solution.
 

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I have been collecting parts for awhile. I have the c7 ZR1 33 spline wheel hubs, 33 spline 6 ball outer cv's to fit them, 31 spline 6 ball inner cv's, 8.8 aluminum IRS diff. 3.73 gear set with 31 spline lsd, Large pinion flange, 1350 u joint flange to match, C6 e-brake setup and rear curved vane rotors.

I need to get the rotors and hubs drilled to 5x4.5in in 14mm holes so the stock Lexus/MK4 wheel studs will work. I will likely use ARP wheel studs. I have 5 lug crown front hubs to keep the stock front offset as well. At this point, I need to draw up a piece to bolt the stock wheel hub to that the 5 lug corvette hub will bolt to also to build a jig like Mike did. I am going to mock the whole arm up in thin wood, then get the pieces made in metal. With the baby and other stuff going on things are slow, but they are moving. lol.
 

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Whistles
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Guess I misunderstood when you said "the whole IRS is going out the door and I'd encourage everyone else to do the same."

Lots of Vette stuff to start looking into, too.

I sure would like to be able to just anti lag like it's built for, and drop the clutch like I see the cool kids doing on TouYube. Probably even pop a wheelie or two, like those folks down in Australia with automatics and stock blocks.
 

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Discussion Starter #17
Guess I misunderstood when you said "the whole IRS is going out the door and I'd encourage everyone else to do the same."

Lots of Vette stuff to start looking into, too.

I sure would like to be able to just anti lag like it's built for, and drop the clutch like I see the cool kids doing on TouYube. Probably even pop a wheelie or two, like those folks down in Australia with automatics and stock blocks.

Yes, whether you're into drag racing or road racing the modern suspensions are independent , can be made to work great in most environments and that's the route i'll be going


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Guess I misunderstood when you said "the whole IRS is going out the door and I'd encourage everyone else to do the same."

Lots of Vette stuff to start looking into, too.
Well if all you care about is drag racing, its hard to beat a solid rear axel.

Vette stuff, I assume you mean for hubs and such. They have rear mounted transaxels, would be a hard car to adapt an IRS from.
 

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Whistles
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Understood. Thank you for the input!
 
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