89 limited slip Ford 8.8 IRS swap help

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Mopar Nate said:
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?
Click to expand...

Once you lay the subframe under your car, you'll start to see why it won't work. In my case I didn't want to cut up my car, so I made the frame to fit the car. If you were hell bent on using the Ford subframe, you'd probably end up doing a complete back half. IE: Cutting the bottom of the car out and building a new structure and sheetmetal. You'll also lose your gas tank and have to run a fuel cell.
If you're going to a wide track, I think you're better off going with one of the full chassis kits that a couple vendors offer. Even if it's not for a Mopar. Like this: http://www.artmorrison.com/ or http://roadstershop.com/
We're talking over the internet here, so I don't know you or your skills. But what you're getting into is some serious money and time if you go this route.
The cost for my rear end I'm not sure of. It wasn't a ton, but I did most all the work and pulled favors on the stuff I couldn't do.
On my Dart, I started upgrading the stock parts first and got it handling pretty good. I also wanted to do something different and that's why I did the IRS. The results were okay, but to really make it good it needed more refinement. I didn't really have the desire at that point to tear the car apart yet again.

I'm rambling now, but bottom line is you need to take a sober look at this. You need to have the money, time and patience to see this through. If I were in your shoes, I'd upgrade the stock suspension so the car isn't down for long periods of time. This keeps your enthusiasm going and the car on the road.
 
dartslantsix said:
Once you lay the subframe under your car, you'll start to see why it won't work. In my case I didn't want to cut up my car, so I made the frame to fit the car. If you were hell bent on using the Ford subframe, you'd probably end up doing a complete back half. IE: Cutting the bottom of the car out and building a new structure and sheetmetal. You'll also lose your gas tank and have to run a fuel cell.
If you're going to a wide track, I think you're better off going with one of the full chassis kits that a couple vendors offer. Even if it's not for a Mopar. Like this: http://www.artmorrison.com/ or http://roadstershop.com/
We're talking over the internet here, so I don't know you or your skills. But what you're getting into is some serious money and time if you go this route.
The cost for my rear end I'm not sure of. It wasn't a ton, but I did most all the work and pulled favors on the stuff I couldn't do.
On my Dart, I started upgrading the stock parts first and got it handling pretty good. I also wanted to do something different and that's why I did the IRS. The results were okay, but to really make it good it needed more refinement. I didn't really have the desire at that point to tear the car apart yet again.

I'm rambling now, but bottom line is you need to take a sober look at this. You need to have the money, time and patience to see this through. If I were in your shoes, I'd upgrade the stock suspension so the car isn't down for long periods of time. This keeps your enthusiasm going and the car on the road.
Click to expand...


Excellent information. Thanks for being the pioneer on something like this. My questions are:

1. You fabbed a new subframe because the available T-bird frame was too wide. Correct? (sorry if I ask the obvious).

2. Do you know if the Cobra IRS subframe would work better (more narrow but expecting to lose the gas tank)

I have an F-body, slightly wider than your A-body and I admit I don't have the fab skill you have. But, I DO have patience, a good mig welder, proper tools and a car I haven't driven since 1980.

Greg
 
dartslantsix said:
Once you lay the subframe under your car, you'll start to see why it won't work. In my case I didn't want to cut up my car, so I made the frame to fit the car. If you were hell bent on using the Ford subframe, you'd probably end up doing a complete back half. IE: Cutting the bottom of the car out and building a new structure and sheetmetal. You'll also lose your gas tank and have to run a fuel cell.
If you're going to a wide track, I think you're better off going with one of the full chassis kits that a couple vendors offer. Even if it's not for a Mopar. Like this: http://www.artmorrison.com/ or http://roadstershop.com/
We're talking over the internet here, so I don't know you or your skills. But what you're getting into is some serious money and time if you go this route.
The cost for my rear end I'm not sure of. It wasn't a ton, but I did most all the work and pulled favors on the stuff I couldn't do.
On my Dart, I started upgrading the stock parts first and got it handling pretty good. I also wanted to do something different and that's why I did the IRS. The results were okay, but to really make it good it needed more refinement. I didn't really have the desire at that point to tear the car apart yet again.

I'm rambling now, but bottom line is you need to take a sober look at this. You need to have the money, time and patience to see this through. If I were in your shoes, I'd upgrade the stock suspension so the car isn't down for long periods of time. This keeps your enthusiasm going and the car on the road.
Click to expand...
Car isn't on the road and has been off for nearly a year now. I'm trying to think long term on the build. Stock stuff is shot and I'm fine cutting on the car so I figure it's better to spend money on the things you want than to keep it limping along with parts you intend to replace. Know what I mean? I'm going to line it up and see how it looks. (fuel cell was part of the to do list already so... we shall see) would it be fine to pm you if I run into anything unexpected?
 
Greg55_99 said:
Excellent information. Thanks for being the pioneer on something like this. My questions are:

1. You fabbed a new subframe because the available T-bird frame was too wide. Correct? (sorry if I ask the obvious).

2. Do you know if the Cobra IRS subframe would work better (more narrow but expecting to lose the gas tank)

I have an F-body, slightly wider than your A-body and I admit I don't have the fab skill you have. But, I DO have patience, a good mig welder, proper tools and a car I haven't driven since 1980.

Greg
Click to expand...

1. Not only is it too wide, it's also too long fore and aft. Mine was out of a 1994 Thunderbird Supercoupe. So many things would have had to change to make it work. In the end, I was able to not modify the car other than drilling a couple holes. Then when I sold the car, I was able to install the regular axle again.

2. Never had the Cobra rear end. It's probably narrower.

I don't have a lot of tools- I did most everything with my mig welder, a drill press and an angle grinder. It was also one of my first big fabrication projects. It was discouraging at times because the car was down for so long. But if you have the will, you can pull it off.
 
wow, that beast must weigh 2X what a solid axle weighs, or a Dana....Nice work, wish I had the time or patience for an undertaking like that.
 
Geometrically too long fore and aft (interferes with how it would operate) or is it just because of the gas tank? Because I'm switching to a fuel cell as I'm lowering the car and would prefer a speedbump not knock a hole in my tank.
 
Mopar Nate said:
Geometrically too long fore and aft (interferes with how it would operate) or is it just because of the gas tank? Because I'm switching to a fuel cell as I'm lowering the car and would prefer a speedbump not knock a hole in my tank.
Click to expand...

One of my goals was to keep the stock tank and keep the car intact. So yeah, the Thunderbird subframe would have eradicated that. The T-bird lower control arms were massive and cast iron if I remember correctly.

Have you got your set up yet? Just throw it under there and start measuring.

On the weight, the car gained about 100 lbs but it also had the tiny 7.25 axle before. I think if I would have refined the design, I could have made it lighter too.
 
Been busy with school starting back ,also been brain storming on some different ways I can get this thing mounted and keep alignment provisions for thrust angle. I'm thinking IF all measures up correctly I can use a similar front mount to the leaf spring front mount and make a rear mount where I can shim the whole assembly anyway I want. I've decided I'll be much better off fabbing up a new upper section of the Diff cage to accomplish that. Weather should be nice all this week here so I hope to get a lot done.
 
No progress, but here's some info I can share. I pulled out my tape measure this morning. It's 38" or a hair more between the top frame mounts on the stock Mustang IRS cradle. If you can get that on a rear A body frame (or close) maybe you can do it.

Greg
 

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I believe wheel mounting surface spread was 6" wider than the A-body drum to drum
on the V-8 T-bird set-up I got. I also don't want to massacre the basic structure of my
'64 GT 'vert, but some concessions will have to be made. If you don't mind running air-
bags, or using a coil conversion kit, lincoln mark VIIIs have alum. lower arms. There are a
few around here, if they can be had reasonably I may grab em as a poss. option. Choosing
FWD style wheels doesn't appeal to me, so narrowing the track or widening the body are it.
Let's see if the OP chimes in and lets us know where he's at with his, I'm still in planning
phase...........
:happy1:
 
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