47-55.1 Thoughts on IRS Suspension

[whitedog76]

Ok, I've been seeing late model Mustang IRS Suspensions pop up for sale regularly. They look very similar in design to the earlier TBird/Lincoln units, with the exception of being wider. Most of us saw Coaches build a couple years ago. http://67-72chevytrucks.com/vboard/s...d.php?t=666720

Of course the late model unit has 20 more years of development into it now, they come with a Torsen Diff., 13" rear brakes, and the Mustang guys are already going nuts with upgrades.

Being wider, is the only downfall I see. They're around 67" WMS, which is a little much for AD trucks. Looking at the subframe, it appears they can be narrowed.

[whitedog76]

Here's one going into a F100, which has several parts, and another going into a 40 Chevy Coupe.

Note: The language is not G rated.

https://www.youtube.com/watch?v=CK4x1n1a10I

https://www.youtube.com/watch?v=Sh9CCM2hPYA

[mongocanfly]

Looks good...haven't seen one of those...but I dont keep up with ford stuff much...would curious about width though....the Vett irs rear works well also

[whitedog76]

The width is the biggest factor. At 67" it's a little much. Looking at the subframe. I bet you could take out 1-2" per side. That would help a bunch.

You can get a 3.15 or 3.31 geared unit for about $500 at the salvage yard. The 3.55, 3.73, and 4.10 units bring a premium though.

Here's a complete setup.

[mongocanfly]

Wondering what the axles look like....are they tubes or solid...could get pricey...just looking at the pic it doesn't look like it would be easy to narrow...

[mr48chev]

I'd have to say that one needs to be able to study one that is out and figure out if it is viable to take probably 5 inches out of the wms to wms witout running into a major redo. Shortening the half shalftsis just $$ to the machine shop but if you can't take it all out of the cradle between the lower control arms you might be in for a huge expense with custom control arms. The "it was just 500 but I spent 2000 on top of that to get it to work" thing that too many of us have run into on stuff that is supposed to be low budget to do.

There are a number of photos here : http://vi.raptor.ebaydesc.com/ws/eBa...79657000&ver=0

Side note, that is the kind of seller I like, clear photos and lots of them and a first rate description

That said, I am not seeing a simple way to narrow it from studying the photos.

[mr48chev]

Any narrowing of the cradle to bring things in is going to throw the axle to lower control arm line up so that it might cause the axle to bind in up down motion.

[mongocanfly]

Never say never...but I'd have to pass on trying to narrow that...I see CV axles now in 48s pic..that alone would blow a budget for custom axles...the frame looks like it may could be narrowed some but I'd want to see one in person before I committed.........but.......for someone with a wms that's close to it, that could use it as is ,that may be a sweet little setup...

[mr48chev]

But there are some real ugly wheels that will work with the and look like you put dualie front wheels on the back..

[whitedog76]

I haven't pulled the trigger on anything, it's more thinking out loud. My truck, a 3600, has an HO52, which is 62-63" wide. So, here's some number crunching. I've seen 65" axles underneath AD trucks, which don't look too bad, wheels stick out a little. If that crossmember can be be trimmed down from 67" to 65, or even 63, that would be the cat's meow. Not having one in front of me, I can't say for sure if it can be done. I'll have to take a tape measure to the salvage yard with me to know for sure.

As far as the CV shafts go, Dutchman can narrow the shafts. $75 a side. There is a long side and short side shaft on these units. So, only 1 side may need to be shortened. As far as binding with the suspension, the inner CV joint is made to slide in and out of the housing slightly anyhow, so I don't see an issue.

I know there is a million little things I'm not thinking of, but its seems highly do-able off hand.

Chris

[mr48chev]

It sounds like you have it pretty well thought out and have done some serious research. That alone may be what will make it work. You also understand the expense. That is a lot better and more reasuring than what we see a lot of the time where guys have ideas but have no clue as to the work or expense involved.

The other thing, if you are running the 3600 as a long bed what would be the problem with widening the rear fenders a tad? Just make a big truck a bit bigger by a couple of inches.

We would have to wake Hogfarm up from his nap to tell us but I am beliveing his fenders are widened a bit. If you can carry it off like he did folks have to be in the know or really looking to tell that the fenders are wider.

[dsraven]

anybody thought of a newer explorer rear suspension? they also run the irs. not sure what they look like though or the track width.

https://en.wikipedia.org/wiki/Ford_8.8_axle

[whitedog76]

Originally Posted by dsraven

anybody thought of a newer explorer rear suspension? they also run the irs. not sure what they look like though or the track width.

https://en.wikipedia.org/wiki/Ford_8.8_axle

I have an 8.8 from an Explorer already. Just haven't gotten around to doing anything with it.

Anyhow, the IRS from the 2004-2011? Explorers were pretty much married to the frame. The only feasible way to do it would be a chassis swap. The Sport Trac wheel base (130" vs. 125.5" in the AD) would be just about perfect from a dimension standpoint to swap in a 3600 truck. They're pretty busy in the rear though. Tubbing and raising the bed floor would be a given.

I've looked at some of the late model SUV/Crossovers. Most of them have drop out rear subframe and diff's also. The problem I'm seeing with them is they typically have weak diff's and there is a lack of aftermarket support.

I've found a few Lincoln LS units, which I like the looks of. Plus they are 61" wide to begin with. They too suffer from a not so good differential assembly.

Anyhow, here's ColbyJack's Aviator/Explorer swap. You can see how busy the back end is.

[whitedog76]

So, I've looked into the Lincoln LS setup a little more. It seems that the Tbird 8.8 center section can be swapped into it with little modification. The LS and the Tbird use 28 spline CV shafts. The upper control arm looks like it could be an issue though. Might not be a bad swap though. I'll have to do some tape measuring. Something more to think about....

[dsraven]

where there is a will there is a way. lol. look what has been done on other suspension mods. get the geometry and make new mounts on the old truck frame
or just stick with a solid axle or a different IRS.
nah, thats what EVERYBODY else does. haha
hotrodding-cobble it, test it, copy it nicer!

[_Ogre]

Overkill unless you're going to race it

[whitedog76]

I've always been one to think outside the box. I am just thinking of something a little different from a standard 8.8 swap. I saw the Mustang unit on Ebay, I wasn't even looking for it. I put "8.8 limited slip" in the google search bar. The Mustang unit definitely got my gears turning per se. No pun intended. It'll be hard to drop a bunch of coin into something especially when I already have an 8.8. I'll even have a GM 8" when I part out my Trailblazer.

[mongocanfly]

there was a guy here that was using a navigator (I think)...havnt seen him here in a while

[dsraven]

got this off a ford truck forum. the boys there were talking about IRS and someone posted this. 2002 explorers started with the IRS.

Bolt pattern is 5-4.5 and the rears will be 8.8's. Track Width (front/rear) 60.9 / 61.2 & axle ratio codes are
41 — 3.27 ratio, non-limited slip.
43 — 4.30 ratio, non-limited slip.
45 — 3.55 ratio, non-limited slip.
D4 — 3.73 ratio, limited slip.
44 — 3.73 ratio, non-limited slip with interactive vehicle dynamics (IVD).


Overall width was 72.1 inches, so the track should be approx 60-62 inches---???


I also found this little series on narrowing a ford 8.8. some q&a's and specs etc. pretty informative if anybody is looking. there is a series of 4

https://thefabricatorseries.com/buil...prelude-and-qa

[1project2many]

Just because I have to say it...

Four link, coils, sway bar, Watts linkage = 200k mile capable production suspension that rides and handles well:





Axle width for vehicle with above suspension is said to be 65" wide.

[whitedog76]

I've actually looked into a Watts setup before. Not opposed to it either. Is that a Durango suspension up there?

I'm really liking the LS setup more and more vs. the Mustang. The LS setup was used in the 99-06 Lincolns, Jag S type, and the abortion of a 2002-2005 Tbird. It's between 60 and 61" wide, which is great for our application. Not to mention they are plentiful and cheap in the salvage yards.

In my research it is very similar in design to the 02-05 Explorer suspension, it's just mounted to a modular crossmember. In fact the Explorer struts and springs can be used, they're only about 3/4" longer. Digging into the Ford parts catalog, the front struts from a Crown Vic can be used also, if a suspension drop is needed.

The 8" center section is different from everything else Ford used. They have a 3.31 and 3.58 ratio, which is pretty good for an old truck. They do not have a limited slip available. My suspicion is that the 8" is in fact just a modified 7.5" diff. Digging through the parts catalog, pretty much everything interchanges between the 7.5, 8, and 8.8 IRS center sections. There is a couple differences in the pinion bearing used, but i suspect that has to do with the Guibo joint on the pinion vs. a standard flange. Anyhow, I'm betting a 28 spline limited slip from a 7.5 will drop right in.

The Ls/Tbird setup uses the 5x4.25 wheel bolt pattern. Again, looking into the Ford parts catalog, The Mustang Cobra rear flange assembly can be pressed on to get the 5x4.5 pattern. Or, just drill the LS hubs and rotor assembly for 5x4.5.

[mongocanfly]

If I wanted irs ,I believe before I'd go to all that trouble I'd just call Don at flat out engineering and order his brackets for the vett rear and use all the vett components... weld in brackets...no narrowing needed....
but that's just me I guess...
It sounds like your doing your homework though so that's good....

[Driver_WT]

Originally Posted by mongocanfly

If I wanted irs ,I believe before I'd go to all that trouble I'd just call Don at flat out engineering and order his brackets for the vett rear and use all the vett components... weld in brackets...no narrowing needed....
but that's just me I guess...
It sounds like your doing your homework though so that's good....

I think I would be going this way too.

Wade

[whitedog76]

Just more thoughts than anything. I got a little ADHD going on. It's been a long winter. I'm finally getting back to work Monday. Heading to Michigan. When I get back maybe I'll have something in the works.

[whitedog76]

Ok, found a bunch of info out there on IFS install.

Also here's a couple pics of an F1, which is kind of where I'd like to go with it, rather than have a low rider.

Here's a really good link. https://www.ford-trucks.com/forums/8...ll-how-to.html