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Discussion Starter · #1 ·
I want to build a fully boxed rear subframe under the back of my Pinto and mount a 3 link with a Fays2 Watt's link, coilovers, and fuel cell.

First, I'm planning to build framerails out of 3x1x11ga off of the stock front subframe, like this:





I want to build the rear similar to this with a fuel cell mounted under the floor:


Here's the Watt's, although I'd be building my own frame and axle connectors (welded to the axle). The center mounts on a subframe with the ends mounted to the axle. They'll provide the propellor, rods, rod ends, mounting plate for the subframe, and the hardware for a damned good price:


And here's the space I have to work with:




The current plan is to build this inward of the current channel rails in the back of the car and then remove the stock ones afterwards. This would also allow me to tub the wells a little later if I wanted even wider wheels. Everything stock will be coming out - spare tire well, gas tank mounts, shock mount subframe, etc. The bumper can be remounted later, I'm not worried about it for now. I can handle figuring out the basic design and how everything is going to fit, but I'd like some pointers.

I was thinking about using the same 3/4 inch rod ends and 1.125 billet arms as the Fays2 Watt's link uses as trailing arms - the company will make the arms whatever length I need and again at a good price.

I'm not sure on how long to make the 2 trailing arms and I'm curious what the best setup for them is - axle mounts and all that. I've seen some shorter brackets that keep the end close to the axle and then longer ones with a lot less ground clearance. Where the stock shocks sit, I'd like to run a boxed crossmember for the upper coilover mounts. I'm also aware that I'll need to account for the arc of the axle when I set the angle of the Watt's link frame.

I shouldn't have much of an issue with clearance as I'm not planning on lowering the car any more than 1 inch from stock - it already sits damned low as it is. The main issue will be fitting the fuel cell and Watt's in with how little length there is, but it is doable. I just might have to go with a smaller cell than I'd like.

I'm mainly looking for advice on what mistakes to avoid. I've never done anything this involved before and want to make sure it's safe and I don't get in too far over my head. I've started an engineering degree but haven't gotten far into it - I don't know enough right now to just jump headfirst into it. I've seen some dangerous and stupid chassis/suspension mods and I don't want to be one of those idiots. I'll probably have a friend who is a certified welder do the welding after I mock everything up, I'm not experienced enough to have that much faith in my welds. I was thinking mostly 1.25x1.25 and 2x1 box tubing in the back, probably 11 gauge. I'm also aware that I have to support the car properly so the body isn't in sag while the frame is being built. If anyone has a better way to do this than what I'm planning I'm all ears, I want it to be strong and I don't want to make the project unnecessarily difficult.

Is there anyone who has good photos of a similar idea that's actually been carried out? I'll try to find time to sketch the idea I have in my head at the moment.
 

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mustang copy

Check out the sub frame kits For 5.0 mustangs, the Fox chassis was the upgraded Pinto to Mustang II design I bought a subframe kit for My Fox chassis capri. I then copied the ladder sub frame kit, I added 1 X 2 tubing under the rockers, and added cross pieces, under the seat and some of the cross pieces line up with the roll bar mount plates. one of the first Pinto test mules bent the radiator support structure when cornering with Fat tires..I added more square tubing to the front top aprons and boxed around the rad supt. Your rear tubing structure will take care of the problems under the rear seat where cracks start with hard driving, suspensiong mounts to floor pan area.
 

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Discussion Starter · #3 · (Edited)
Are you talking about a rear subframe upgrade kit and not connectors or a front subframe? I can't find anything about a rear kit from a quick search but I'm seeing plenty for front clips and subframe connectors.

I found a good diagram of the stock rear setup with a 4-link:


I was planning to run 2 main rails back to just past the axle like a normal ladder frame, then the tubing structure right after the Watt's for the bumper and fuel cell.

I know I'm definitely going to have to reinforce the front end before I start beating on the car after swapping the motor. I want to get the rear end done and get my new drivetrain in and have the car drivable before I start on anything else. Definitely planning on adding tube structure to the nose and possibly reinforcing the firewall.



I also never thought of mounting the coilovers to the trailing arms. Interesting idea, but I figure I'm better off mounting them to the axle similar to how the shocks are currently located.
 

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global west

I used the Global west sub frame kit , which is for the center floor pan, the same length as the rocker panels. but modified my single tube kit to be stronger than their competition kit, My cross brace under the seat goes clear to the tunnel, more cross pieces and ones for the roll bar mounting locations. global west has pictures on their web site. another area to check out is the cowl lower panel . it was designed as part of the load bearing structure. . leaves and trash can get inside and rust- rot- weaken the bottom panel. a lot of roll cages add the cross brace in the instrument panel area.
 

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Discussion Starter · #5 · (Edited)
I'm not going to worry about the cowl and the front end yet, I've got enough on my plate at the moment. My plan is to do one thing at a time and have the car in running, driving condition as soon as each project is finished. I'm assuming my cowl has some rot even though I haven't seen water run in from it yet. I know pine needles have been getting caught in it since I've owned the car.

After doing some research and looking under the car, I realized 3x1 tubing wouldn't be the best idea and I'm having the guy at the welding shop across the street from where I work get me a price on 3x1.5 and 3x2. He can get in a 24ft section for me no problem when he has his steel dropped off. I'm leaning towards 3x2 and I think I'll run it all the way to the back. The Global West kit looks pretty interesting and after seeing it I'll probably run a small diameter round tube next to the rockers later on connected to the main rails. Do you have any photos of the setup you made?

I also want to run 2 crossmembers that go over the driveshaft. I was thinking of bending some 3/8" or 1/2" plate to match the shape of the tranny tunnel and putting that in the middle of a 2x1.5 box section or something. Basically like the top half of a driveshaft loop, but make it part of the crossmember. And possibly have a removable brace below the shaft too.



Basically like how trailer hitches are made, because it'd add some structure to the car and keep the driveshaft from coming into the floor if something breaks:
 

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No picts

No picts, I didn't take any whenI was building it, but like the GW competition as above stated. I also had some crackes on the fox chassis where the control arm mounts attach to the floor, (coil spring suspension ) I added some angle iron inside under the rear seat. The 65 Shelby mustang competition models had an added tube crosmember inside the car (no rear seat) ,in the area close to where the front of the rear springs mount.
 

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Discussion Starter · #7 ·
So I think my best option is a setup like the TCI one:


But with traditional style rails going all the way to the back like I was already thinking. I completely forgot that I'm going to need a torque arm. I emailed them to see if they'll sell the torque arm assembly from their Mustang kit separately. I know I can handle the control arms, coilover mounts, etc myself but I can't handle making a torque arm that'll work well.

And I may go with a panhard bar for the time being, just to make things simpler. It'll be difficult enough to build the setup anyways.
 
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