IRS measurements

[Jedidiah55]

Hello, I've joined this forum because I'm strongly considering putting the 3rd gen coyote in my 68 mustang. I'm just trying to get all my homework done before I start buying any big ticket items. One issue is what to do with the rear end. I am curious if I can fit a 3rd gen IRS set up under my car. But I fear its way to wide and also the mounting points might be an issue. I was wondering what is the width on the rear end and the is the distance between 4 bolts that connect it to the frame?

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[RazzaRossa]

I think this would be a lot of work, but maybe that is what motivates you, the challenge and uniqueness. Will it work? I don't know, but you can fabricate just about anything. There are kits out there already designed for '67-'68 Mustangs (Heidts), I did a quick search
http://www.mustangandfords.com/how-...independent-rear-suspension-in-a-1968-mustang.
There are other options that may require a bit more work, such as Factory Five Racing's IRS kit.

Here is link for someone doing '67:
https://www.ffcars.com/threads/1967-mustang-irs.261313/
Or there is the SN195 Cobra IRS, which is similar to the T bird IRS of the same era. Sounds like a fun project. I had a big block '67 4 sped car that was kick ass fast in the1/4 mile, it left A LOT to be desired in the stopping and steering department, but I loved it anyhow. Best of luck and when you get tired at some point in the project, step back, take a break and come back and kick it's behind to finish it all the way.

 

[Jedidiah55]

If its not too hard to throw it up there, then Ill buy a wrecked mustang pull and build the motor and take the rear end. If it require too much fabrication then Ill just buy a motor part by part. The big thing is I dont want to mod the gas tank. For the front end I'm buying a Mustang II kit. I get to dropped the coyote engine mounts, disc brakes, power steering, coilovers. But for the rear end I don't like most of the options (trim gas tank, drag setups). The new mustang IRS is easier to get than a cobra. My budget is decent 20+k (its more as long as the wife doesn't kill me) but after paint, motor, trans, front end, wiring, ecu, A/c, tuning, and the random parts eat a lot of that up. I'm not set on what I want to do with the rear end. I want some power under the hood, but ride quality is up there.

 

[MRGTX]

What is your goal for the car? If it’s just to have a fun to drive classic Mustang, strongly consider more conventional setups first. You can get anything you want in terms of differential style, gear ratios, widths, etc... these are pretty plug and play so long as the spring perches are in the right spot...and these can be moved by anyone with basic welding skills.

I wanted to make my old Mopar into a decent handling car. I looked into IRS and while it has huge advantages over a solid axle when cornering over bad pavement, 95% of the time, you won’t even know it’s there. The complexity, cost and weight gain made it not worth the trouble. In the end I ended up calling Moser and ordering a 8.75” with an Eaton Truetrac mechanical limited slip, 4.10 gears and disk brakes. It was a perfect fit, works flawlessly.

Here’s one of their packages that can be ordered to fit your car. You can mix and match components but this is the ballpark for a basic, solid setup that would handle your Coyote easily...https://www.moserengineering.com/Moser-M88-MUSCLEPAK.item

I would discourage you from going nuts with a 9” or a Dana 60. Yeah, they’re stronger but they weigh a lot more (Which really hurts handling) and they sap more horsepower to turn. Buy only what you need for your setup and you’ll be happier.

If you want to spend less money, any Ford 8.8” from a Mustang, Explorer, etc can be made to fit, IIRC, Explorer rears are often 3.73, limited slip and come with disk brakes. You may need to mess with the parking brake cable and you will have one of the axle tubes shortened (Off center diff in the Explorers)...but you can end up with a super strong rear axle assembly for $600-$800.

A classic Mustang with a high revving Coyote is going to be awesome no matter what. Good luck!

 

[bauern]

This is from Kohr Motorsports web site for a 2015 assembly:

"Approximate measurements are listed below…
Hub-To-Hub Spacing: 66-1/4”
Rear Bushing Spacing: 37-3/4”
Front Bushing Spacing: 40-1/2”
Front-To-Rear Bushing Spacing: 20” "

 

[Jedidiah55]

Sweet thanks.

And yeah I might grab 8.8 and go with a 4 link. I want to build a rear end for 700 hp just in case I want more power in the future.

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