89 limited slip Ford 8.8 IRS swap help

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Mopar Nate

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Anybody done this swap? I am going to do it but I'd rather not reinvent the wheel if at all possible. I plan on doing a full write up with pictures and all but will take any advice or ideas I can get. Thanks in advance. (Going in a 71 duster if it helps any)
 
Are you planning on using the OEM frame mounts for the sub frame or building your own control arm mounts? Very interesting, love chassis work.

Can't help as I back halved my son's '88 Mustang installing shortened Mopar 8 3/4" with ladder bars. I know more about Mustangs than I ever wanted to so I'll be following with interest.
 
If you go this route, you will be re-inventing the wheel... I've never seen such a thing around here. Get ready for the blasphemer crowd.
 
What is this IRS out of? I can't think of any Ford with IRS in 89... Town Car?
89 thunderchicken... the one I was lucky enough to grab is a 3.73 limited slip out of the turbo car. Im going to attempt to use the part as is and just create mounting brackets... but if that fails I`ll create a new cage. The benefits here far outweigh the hate from other people who see no reason why I should want a little negative camber (the plan with the car is rack/coil over ifs & a t56 its all curves where I live so driving the car stock made life a lot less enjoyable)
 
Go for it, I was looking at that swap also, bur useing 90's Mustang.(5 lug)
 
Pretty cool idea. But if I may ask, what are you gonna do with the car? Are you sure you're gonna need all that, or is this something you are wanting to do more than need? Either way it will be cool.
 
Pretty cool idea. But if I may ask, what are you gonna do with the car? Are you sure you're gonna need all that, or is this something you are wanting to do more than need? Either way it will be cool.
I like to be different... life is too short not to try different approaches... plus I figure being 19 I can use any learning experiences I can get. I try to be reasonable and understand some things are better left alone but modern, or in this case more modern than 71, technology is worth exploring if we want to keep these old cars going... my generation is losing interest in the old way of doing things and if we want to get them interested in something besides rice then we have to modernize. That being said yes it is probably a bit much but oh well its only $... cant take it with us.
 
so after brainstorming at work all day... I think I've got some ideas... Going to be doing a lot of drawings and cardboard work before any welding or cutting so any ideas are appreciated.
 
my generation is losing interest in the old way of doing things and if we want to get them interested in something besides rice then we have to modernize. That being said yes it is probably a bit much but oh well its only $... cant take it with us.

This is true, but what about other more worthy upgrades? Leaf springs work fine bro. I'd dump money into the front end first.
 
This is true, but what about other more worthy upgrades? Leaf springs work fine bro. I'd dump money into the front end first.
I don't have much $ in the rear at the moment and I have another thread open for the front suspension. Been discussing pros and cons of different systems. After taxes comes back I'm going to buy a t56 or tr6060 or the front end. The plans I currently have are going to require a custom driveshaft so I'll have to get everything together before I can even think about getting this car back on the street. Also destroyed the 7 1/4 currently in the car with my engine rebuild and an ignorant decision in my old high school parking lot (that's when I parked the car for a ground up restoration and modifications).
 
I like to be different... life is too short not to try different approaches... plus I figure being 19 I can use any learning experiences I can get. I try to be reasonable and understand some things are better left alone but modern, or in this case more modern than 71, technology is worth exploring if we want to keep these old cars going... my generation is losing interest in the old way of doing things and if we want to get them interested in something besides rice then we have to modernize. That being said yes it is probably a bit much but oh well its only $... cant take it with us.

Google "Green Brick Valiant" and read about it.
 
if we want to get them interested in something besides rice then we have to modernize.


It can swing the other way, too. Being only 19, means you have no idea that it's all been done before. IRS is nothing new. These cars are a good mix of things that work and last. Like I said, google the Green Brick and read about it. That car was racing with and beating Vipers, Vettes, Ferraris, Lambos...you name it. Its all about the package. Usually, cars are pretty tough to improve upon from the factory design. It can be done, but it's a lot more difficult than simply swapping in "better" parts.
 
It can swing the other way, too. Being only 19, means you have no idea that it's all been done before. IRS is nothing new. These cars are a good mix of things that work and last. Like I said, google the Green Brick and read about it. That car was racing with and beating Vipers, Vettes, Ferraris, Lambos...you name it. Its all about the package. Usually, cars are pretty tough to improve upon from the factory design. It can be done, but it's a lot more difficult than simply swapping in "better" parts.

Absolutely. There's a lot of really fast cars with good old straight stick rear axles.

And, it really depends on the parts you swap in. I spent the last couple of hours reading up on Mustang IRS. Seems like the only way you'll get rid of the wheel hop that's been associated with that particular design is to replace every rubber bushing in the entire system with aluminum or delrin. And of course, if you lower the car you'll have to completely re-do your alignment and modify some things to avoid bump steer. Not sure if that's relevant though without knowing how it would install, might not need to lower anything.

Seems like the racer's still like the IRS better, but they're heavily modifying the stock system. The Mustang Cobra set up is nice because of the cradle it comes with, turns out the 99-04 Mustang chassis was a modified earlier version, so the IRS was added just like we would have to do it. Bonus, easier to install. Negative, that's where all the bushings and wheel hop come from.

Seems like the dimensions of the Cobra IRS are close enough to make a swap realistic. Guys have put them under classic mustangs as well, so it can be done. I'm seeing a to hub-hub dimension of about 62" to 62.5" for the 99-04 cobra IRS, which is a little wider than the B body rear I have in my Duster (60 1/8" drum-drum). So, even more backspace will be needed than what I have, which is 7" on my 18x10's. The only dimensions I can find for the cradle mounts is about 40", which is almost exactly the center to center measurement on our rear frame rails. So, that might work pretty good.

But its not a small undertaking. And if you just bolt up an IRS from a donor car you'll get all the wheel hop issues that the 99-04 mustang guys have been complaining about since they came out. Seems like you would definitely end up being into it for thousands, even if you get the IRS complete from a donor car. Still, compared to converting to a 4 link and disks its not a horrible price. Heck even compared to sourcing an A-body 8 3/4 and disks it might not be too much more painful.
 
For me it is largely for learning... if a mistake is made it can always be fixed (usually). In my mind I feel the IRS system has a lot of potential and a good 8 3/4 with a 4 link for handling is a bit pricey. If this was going to be a car intended to run in straight lines and undertake clutch shattering take offs... Straight axle without question. But I live in the mountains and can run like -1 to -3 degree of camber on the rear with an IRS and I know a lot of guys hate this new stance thing but in moderation its actually beneficial and much like the way you'd camber a short track car. Again the stock stuff on the car is shot.. meaning at the very least I would need an 8 3/4... which is pricey and kind of light... I'm actually looking at adding weight to the rear and pulling it from the front closer to the 50-50 number. I took some measurments and it appears that the rails under the duster are extremely close to where the rear mounts. The rear mounts will be a little inboard almost on the money and the front will be a little outboard. I am going to cut the trunk out due to rust so that should help me out a little. Been going over some ideas about a wide body look for this car with my stepdad (went to college for auto body) and it looks like the dimensions for the rear are good and I dont need as much backspacing as you might think.
 
Hmmm...

That looks pretty doable. Wonder how the A-body rear rails match up to that set up...

Well.... F-body looks pretty good.

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Just sayin'....

Greg
 
I've done it in a '66. Here's a series of articles that I wrote on the project:
https://dartslantsix.wordpress.com/2014/06/27/1966-dodge-dart-irs-project-part-1/
https://dartslantsix.wordpress.com/2014/06/27/1966-dodge-dart-irs-project-part-2/
https://dartslantsix.wordpress.com/2014/06/27/1966-dodge-dart-irs-project-part-3/
https://dartslantsix.wordpress.com/2014/06/27/1966-dodge-dart-irs-project-part-4/

The entire subframe won't work for a number of reasons that I talk about in the articles. Not sure how good your fab skills are, but it is a lot of work. It took me about two years to get everything working. Good luck.
 
I've done it in a '66. Here's a series of articles that I wrote on the project:
https://dartslantsix.wordpress.com/2014/06/27/1966-dodge-dart-irs-project-part-1/
https://dartslantsix.wordpress.com/2014/06/27/1966-dodge-dart-irs-project-part-2/
https://dartslantsix.wordpress.com/2014/06/27/1966-dodge-dart-irs-project-part-3/
https://dartslantsix.wordpress.com/2014/06/27/1966-dodge-dart-irs-project-part-4/

The entire subframe won't work for a number of reasons that I talk about in the articles. Not sure how good your fab skills are, but it is a lot of work. It took me about two years to get everything working. Good luck.
Good read.:study: Thanks for the links. I'm definitely going to buy that book you noted in your article. I'm going to head to the drawing board ASAP. A few questions though. Why couldn't the stock cage mounts be modified to mount to the frame rails under the car? Seems like that would solve a lot of your structural issues? Did it incorrectly distribute the weight that way or was it just a clearance thing? Also what if the frame rails were cut and fabbed differently? I'm ok with the stock length of the half-shafts because I plan on squaring the car up and extending the front end out a few inches as well for a larger track width(looking at some wide body ideas for body work). What was your total cost developing the prototype?
 
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