Putting IRS in my 65 Mustang

[Dazecars]

Thought I would post some information about a little project I am working on. I have always had a fascination with the idea of putting Independent Rear Suspension in my mustang, and due to this interest have done lots of research involving corvette IRS, Cobra R code IRS and aftermarket options. All of which were big $$ and problematic especially with the narrower 65 and 66 cars. There was also part of me that wanted to stay Ford. Even though I figured that this suspension upgrade was beyond my means it still was persistent thought in my mind, kind of like a tickle in the back of the throat that wont go away no mater what you do and so I kept looking for a low cost unit from a Cobra R code, but new I probably wouldn't find one for less than $1000. Back in January I did an eBay search and found a trick IRS unit and made a post about it on another forum. Any way one of the responses told me that basically what I was looking at was an aftermarket Jaguar IRS unit. As I began to research the mater I found that the IRS unit Ford designed for the Mustang was loosely copied from the jaguar, and used the Jaguar center section. Yes for you skeptics and disbeliveers Arning of Ford designed an IRS unit for the mustang and it was installed on 5 prototype cars all of which I believe were falcons. It was supposed to be an upgrade available on the production line, but sense the Mustang was already selling so well the design was scraped to save time and money. If Ford was going to use it, well then so could I especauly sense Ford now owns Jaguar. With further research I found a complete Jaguar assembly could be had for much less than other options. SOOOOOOO I bought one and have been working on rebuilding and narrowing it to fit under my car. Below are links to posts I have made on another forum for your viewing pleasure. As always I am taking lots of pictures and will be writing several articles for my web site www.DazeCars.com with all the details on this project. Please look over what I have done so far and all opinions ARE welcome

http://members.boardhost.com/MustangSteve/msg/1170260249.html

http://members.boardhost.com/MustangSteve/msg/1171423905.html

http://members.boardhost.com/MustangSteve/msg/1171941995.html

http://members.boardhost.com/MustangSteve/msg/1172113881.html

http://members.boardhost.com/MustangSteve/msg/1172291840.html

http://members.boardhost.com/MustangSteve/msg/1172521179.html

http://members.boardhost.com/MustangSteve/msg/1172593789.html

http://members.boardhost.com/MustangSteve/msg/1172984468.html

http://members.boardhost.com/MustangSteve/msg/1175269680.html

http://members.boardhost.com/MustangSteve/msg/1175573124.html

 

[mustbereel]

irs

I know that tickle. I looked at the early Ford IRS, the modern Cobra stuff and finally settled on Heidt's. I love the idea of adapting the Jag IRS to your Mustang. I've finally had a chance to drive the car a little and although I haven't thrown it around much the differnce is huge. The car rides much better but the main difference is that unlike a solid axle the IRS dosen't let you know it's there. It makes the 3-link in my 06 feel crude. Bumps on a corner under power? No jumping sideways! It even hooks up better than I expected.

I look forward to seeing how your's turns out. I haven't ruled out IRS for the 67 coupe I just picked up.

 

[RogerC62]

I've had that tickle for a while myself. I'm set on one of two units for my 69, CWI's ford center section unit or Heidts. I had an 89 Tbird and loved the ride and handling with the IRS. Too bad I had to use it as a trade-in or I may have adapted the rear to the stang.

 

[351w_swap]

That looks like far to many modifications to the rear for me but if you can do it, have fun with it. I thought about going with heidts irs but opted for a much cheaper 4 link setup. Post up some more pictures when you get it all done.

 

[Dazecars]

here is somthing you may find interesting. below is a heidt's unit.

and below that is a Jaguar unit that was narrowed up and put in a Mustang

Other than the cage on the Jag unit, the difference in LCAs and the hubs (heidts uses a hub design based on the corvette hub) the heidts unit is a direct copy of the Jaguar unit. In fact I found that most aftermarket IRS builders use a variation of the Jaguar unit. If you decide to go with a Jaguar IRS in your new mustang you have the added advantage of a heidt's unit to compar it to.... and all the info I am finding and documenting on my build

 

[351w_swap]

They look very similar, both look like a real PITA to do a brake job.

 

[bnickel]

i've always wanted to do an irs as well. my plan has always been to base mine on the 68 shelby prototype unit in the EXP500 mule car, also known as the Green Hornet. the cool thing about that one is that it uses a 9" center section and is very similar to the jag/CTM engineering unit, except that it actually has upper control arms unlike the heidts or CTM units. it also uses a cradle, kind of similar to the cobra irs. it's also a 4 link style in addition to the upper and lower control arms. the guy that re-created it (the original irs was long gone) back in the 80's used cougar/t-bird hubs but one could also utilize cobra pieces if they wanted. my plan is to build one of these IRS units for the 69 cougar i'll be getting soon at some point in the future, though i may end up using a cobra IRS instead, it just depends on my resources at the time

 

[RogerC62]

The ford 9" CWI IRS

 

[Dazecars]

I thought about putting a 9" in my Jaguar set up, but the thing is the Dana 44 that comes in the Jag unit (actually it is not a dana 44 but rather a suslbary unit, which means it is similar, but different, and can use Dana 44 parts with the correct bearings and seals) is more than strong enough, and its more than $1000.00 to make the swap. I was able to sell the new ford 9" track lock differential I had and use the money to buy a locking Dana 44 carrier as well as a full rebuild kit.

 

[ForceFed70]

I thought about putting a 9" in my Jaguar set up, but the thing is the Dana 44 that comes in the Jag unit (actually it is not a dana 44 but rather a suslbary unit, which means it is similar, but different, and can use Dana 44 parts with the correct bearings and seals) is more than strong enough, and its more than $1000.00 to make the swap. I was able to sell the new track lock differential I had and use the money to buy a locking Dana 44 carrier as well as full rebuild kit.

If it's built on a Dana 44 design, then why do you think it will be more than strong enough? The Dana 44 is nearly identical to the GM 10 bolt (GM got tired of paying royalties to Dana and just copied the 44 and called it a 10 bolt). In fact, many parts swap back and forth between the 2 axles.

Anyways, the 10bolt an Dana 44 axles are notoriously weak. You can buy aftermarket parts to strength it up, but in the end you'll end up spending more than the 9" would cost, and still not have the same strength.

I don't know what your plans are for the car, but with all the work going into the IRS, I'm sure motor work, etc has been done. Depending on wheel/tire combo I'd say that 300hp would be pushing it.

 

[coolblue65]

If it's built on a Dana 44 design, then why do you think it will be more than strong enough? The Dana 44 is nearly identical to the GM 10 bolt (GM got tired of paying royalties to Dana and just copied the 44 and called it a 10 bolt). In fact, many parts swap back and forth between the 2 axles.

Anyways, the 10bolt an Dana 44 axles are notoriously weak. You can buy aftermarket parts to strength it up, but in the end you'll end up spending more than the 9" would cost, and still not have the same strength.

I don't know what your plans are for the car, but with all the work going into the IRS, I'm sure motor work, etc has been done. Depending on wheel/tire combo I'd say that 300hp would be pushing it.

I think you are mistaking the Dana 36 for the Dana 44, the dana 36 is notoriously week in racing applications, the case itself is a weeker design then the 44 as well as the gears. The Dana 44 is very tough in the IRS version, it is used in Vipers and manual trans vettes, the half shafts on my vette are a solid 3.5' (or 3.75") diameter.

They are also the straight axle dana 44's out there which you may be referring to as week- but they don't share really any parts with the IRS, so I can't speak to the straight axle versions.

 

[ForceFed70]

Hmmm, I will admit that my axle knowledge is all solid axle. So maybe things are a little different when it comes to independent setups.

But I was thinking of the D44/10bolt. I've gone through 2 D44's and a 10bolt axle in the front axle of my truck. And usually you can get away with a weaker front axle than rear. But in all fairness, I am running 35" mudders.

 

[rbohm]

Hmmm, I will admit that my axle knowledge is all solid axle. So maybe things are a little different when it comes to independent setups.

But I was thinking of the D44/10bolt. I've gone through 2 D44's and a 10bolt axle in the front axle of my truck. And usually you can get away with a weaker front axle than rear. But in all fairness, I am running 35" mudders.

thats your problem with the dana 44. them tires need alot of torque to turn, and they stress the axle rather significantly. in street car applications with smaller tires, the dana 44, and the gm 10 bolt both work reasonably well in stock to moderate hp applications.

 

[bnickel]

i'm fairly certain that a good welder can cut a stock 9" housing down and weld on all the required bracketry to make it work in place of the D44, in fact that was exactly what was done on the Green Hornet. the biggest expense would be from cutting down the stock axle shafts and resplining them for the, now, very narrow center section. basically the IRS setup in the Green Hornet car is a Z-link (4 link with front and rear bars) and has both upper and lower control arms and outboard disc brakes. the stock jag inboard disc brakes are a nightmare from maintenance standpoint so the outboard discs are better though they have a bit higher unsprung weight than the inboard discs. the original Green Hornet used stock 68 front disc calipers and rotors, IIRC.

 

[Dazecars]

BottleFed70
A Dana 44 even in the solid axle form is rated at 500 foot-pounds of torque. The Z-spec T5 in my car will fail before the Dana will. The truth of the matter is my car has a performance 289 and is not a drag car. If I was going to go with 18" slicks and a 500 HP motor than I would not hesitate to go with the Ford 9" but sense I am not going to be doing that nor am I gong to be dumping the clutch at 5000 RPMs I am sure the Dana will be more than strong enough. IMHO for most upgrading a Jag to a 9”, It is no different than those (non drag racers) who insist on replacing there ford 8" with a 9" simply due to the thought of bigger is better. An 8” can handle 400 foot-pounds of torque there again a T5 will blow up before a ford 8”. The only reason I was going to upgrade to a 9" was better gear options and more affordable track lock units.

bnickel
As far as modifying a 9” center section to work with a jaguar set up I was going to do that. I have a special jig for shortening rear end housings to any length, and as you can see from my posts so far, I like a challenge . The reason I decided against shortening my own had nothing to do with the housing and everything to do with axle length. A jaguar center section is 14” flange to flange. The minimum you can narrow down a 9” center section to is 12” So there is only enough room for 1” from the edge of the housing to the end of the axle flange. On the aftermarket units designed to work with a jaguar IRS unit the space between the axle bearing and the axle flange is only about 1/2” where as a stock axle is 2.5” or more. There was no way for me to do it with out having customs axles made from scratch which when I looked in to is was going to cost more than getting a 9” center section from the companies that already sell them.

 

[6T6coupe]

The Jag rear is plenty strong and there are lots of ways to make it stronger. Jaguars have been racing on versions of that rear since the late fifities and the weak points are known and correctable. If the intent is to drag race with big power, slicks, and nitrous, IRS is probably not the way to go anyhow. But it seems like dazecars has done his homework, knows what his intended use is going to be, and is planning accordingly.

One other possibility for consideration is the Factory Five IRS. It utilizes the 8.8" T-bird/Cougar/MkVIII/Explorer center section. It's tough enough for high powered Cobra replicas with meaty tires and is not outrageously expensive.

The big advantage is that it can use commonly available gears, bearings, brakes, and other Ford parts. There is a narrow version that should fit the 65-66 pretty well and allow fairly good size tires. Actually, the standard 59.25" width rear should allow you to use SN-95 wheel backspacings of 5" to 6" within the 65-66 body. The cage can probably be adapted to the unibody easily and it's pretty much self contained.

 

[allcarfan]

I know that tickle. I looked at the early Ford IRS, the modern Cobra stuff and finally settled on Heidt's. I love the idea of adapting the Jag IRS to your Mustang. I've finally had a chance to drive the car a little and although I haven't thrown it around much the differnce is huge. The car rides much better but the main difference is that unlike a solid axle the IRS dosen't let you know it's there. It makes the 3-link in my 06 feel crude. Bumps on a corner under power? No jumping sideways! It even hooks up better than I expected.

I look forward to seeing how your's turns out. I haven't ruled out IRS for the 67 coupe I just picked up.

Any other info on your heidts unit? write up of the install? I have been looking at one for my car. Other than what comes in the heidt's kit, what else was needed for the install?

Thanks

 

[truck90278]

I would suggest touching base with Kugel Komponents. He was one of the first (20? years ago) to use Jag IRSs in street rods and other conversions.

 

[mtbdoc]

The FFR approach is interesting...and it is very reasonable in cost (<$2000). I remain totally unsure of what to do w/ my 65 2+2 as far as suspension. $4000 for a 3-link setup, still needing brakes and axle...an IRS might not be too bad an idea.

 

[mustbereel]

Heidt's

Any other info on your heidts unit? write up of the install? I have been looking at one for my car. Other than what comes in the heidt's kit, what else was needed for the install?

Thanks

Allcarfan,

Check the Reenmachine sticky on top. He has info on the Heidt's IRS install.

For my install check my thread:
http://forums.stangnet.com/showthread.php?t=656858&highlight=mustbereel

It's not a strait forward installation and requires lots of fabrication. If your still interested after looking those threads over send me a pm and I'll be happy to send more pics and answer questions.

edit: now that I look at my old thread there's not much info on the IRS. I know I've posted more info somewhere.