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Laprosonic built up the Starfighter several years ago (2010) The pirate post chronicled the trials and tribulations. He, and friends did finish the rig and ran it at KOH. It is beautiful and well thought out. Interesting was having to re-think the IFS after about half done. We all learned a lot fropm that effort, and started looking at the Built KOH rigs with more knowledge....or better yet...questions.

We certainly learned about SIZE of parts and consequences. Both in fabrication and racing.

Laprosonic had issues trying to get the qualifying run finished as I remember. He has since run it recreationally, having lots of fun. It is one thing to have something that bitchen and then almost recklessly smash it thru the rocks to qualify for doing more damage. KOH is a test but also a commitment.

http://www.pirate4x4.com/forum/general-4x4-discussion/912264-last-starfighter-ifs-build.html

This should help appreciating what is going down here........
 

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I wouldn't go IRS without A-arms. It takes a lot of work with suspension geometry... blah blah handing
Define "A-arms" IIRC there's some pics in the IRS thread where someone mounted the diff in the center of one A-arm and stuck a CV in the center of the chassis where the A arms meet. Sure you've got the A-arm handling rotational torque from the diff but any A-arm suitable for the kind of use we care about here shouldn't care about that. With a wide housing like a 14b I'd be looking to do something like that.

With a fullness truck wheelbase you won't notice a lot of geometry sins in the rear especially at the limits of travel. Just look at how much a typical OEM solid axles move around under stock suspension travel. Similar numbers at greater travel should handle fine. A tire that's near full droop won't be doing much good when it comes to directing the vehicle anyway, especially on the kinds of terrain where you'll have a tire at full droop.

Getting suspension geometry dialed in over a large amount of wheel travel is one those things where you spend 90% of your resources on the last 10%. If you're not racing to win then you should probably spend your resources elsewhere on the build.

If 8-10 inches articulation is OK. You will have something beefy that the CV's might not take...unless 30 series @$1k each.
Obviously operating angles aver very much width dependent but I don't see why he couldn't use U joints. GM did it just fine in the Corvette. For the amount of plunge he'll need to handle and U-joint sizes he'll want it's possible that he can use of the shelf MDT or larger truck parts.


There's a independent rear end out of a 60's Jag that uses a Dana 44 housing..
Future hot rod build!! Found it in a junk yard scrap vehicle last year.. They gave it to me for $100 as is.
Swapping a Jag IRS into things has been a thing for a very long time. As far as OEM IRS goes there's far better stuff available today. The Armada has a similar D44 based IRS but it's one of the weird D44 models with limited aftermarket options. The Ford 9.75 IRS is probably a better starting point for most builds at present.

I am going to machine a bearing retainer similar to the semi-float style OEM design
You could press a bearing into a retainer and onto the flange/shaft like a 80-81 TTB center joint. Depending on the bearing you use you may be able to countersink it into the housing so that the overall width of the assembled housing is only increased by the width of the bolt flange on the retainer.
 

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Discussion Starter #23
Yeah I saw the rig you are referring to with the diff mounted to one of the A-Arms. It's definitely thinking outside the box but I am not convinced this is the way to go. I totally agree with you about the bearing retainers. I am going to tuck the bearings in as close as I can into the housing as to get as narrow as possible. And yes I am not going to use CV joints for this rig. RCV Quoted me over $11,000 for shafts/joints. I can put together some MDT components for much less.

The Jag rear end was just a fortunate find. Yes there are better rear ends available today, bot not at this price. The new mustang drop outs are 10x-15x more expensive than what I spent.
 

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Call Thom at Spidertrax or Julene at Summit Machine in Utah. They can easily make special billet stubs to fit a 935 or 30 series CV. Budget would be easily 1/2 of RCV including cv's. Julene made stubs for my 9" IFS center. I also paid for the longer spare with longer splines. If I broke the short one, I could cut the longer to fit....and order another without a rush commitment. At one time I also had Moser make stubs to fit a shortened model 44 center like yours. I would expect Currie to be set up for multiples so a remote option.
 

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Our first go at IRS was Corvette outers and a shortened D44 center with U joints in '66. It was used as a Drag Jeep. I bought it and started bending swing arms from HP and traction. I did break a stub shaft once as we just welded ends to a stock axle. :). In that set-up we used driveshaft parts that slipped together for plunge. I am constantly tightening 5/8" flange bolts. And replacing Joints at 8" suspension (78" OoT).

About'80 I built two IRS for friends with the 80 Corvette D44 center and fabricated arms with the Corvette hub. In those I went with the stock stubs and let them plunge in the center bearings and Locker. No issue still. Did I already mention that? Works perfect and never changed seals either....But neither are mud boggers. Mainly sand and trail.

At speed, I wouldn't take a Ujoint above about 12* but the "rule" for CV's has been 22* and lately 24*. In Ultra4 IFS many are running 22* and then up to 45* for turning. The 22* rule seems to stem from Class1 cars that plunge up to 2" and probably where much of the heat comes from. They are definitely a maintenance PITA!!!

For arse-sideways: The 80ish Corvette alum center doesn't have any aftermarket help. I bored the mains to accept a standard Dana 44 locker. I used the outer roller bearings to align a thru rod. I put a lathe tool through it and bolt clamped. It took some diddling but I got it to the right boring diameter and used a 1/2" drill motor to spin it. Sketchy as hell but got three done without ER.

Edit since we are all thinking: The Armada IRS that I know about is Cody Wagoners. I am pretty sure the center is a $30k trick narrow Weismann with bull gears, but a model 44 might be enough strength for the portal hubs that are also being used. The Dune Masters club (SoCal) has been using Thunderbird IRS components with success also. They run BIG motors, but don't have the driveline shock loads like dirt offroad...and limited travel..

Lately I looked at the Mustang rear IRS because doing what I thought was easy...wasn't. What i saw in that system was a crutch link to prevent the arms from wrapping up like a dish rag when stopping. Their solution apparently works for them but wouldn't with our big heavy wheels and BIG brakes. I do know there are several aftermarket systems for the Mustang so maybe they saw the same issue ..or??? Some beefed the centers maybe with 10" gears? By then, I was not that interested. The a-arm positioning is very unique, but look for the unintended consequences of good forward bite.
 

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I just sent an email to DynaTrac about doing a 60... I've yet to hear back from them...
Your work looks great, and I'll be subbing this...
 

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The 80ish Corvette alum center doesn't have any aftermarket help. I bored the mains to accept a standard Dana 44 locker. I used the outer roller bearings to align a thru rod. I put a lathe tool through it and bolt clamped. It took some diddling but I got it to the right boring diameter and used a 1/2" drill motor to spin it. Sketchy as hell but got three done without ER.

Edit since we are all thinking: The Armada IRS that I know about is Cody Wagoners. I am pretty sure the center is a $30k trick narrow Weismann with bull gears, but a model 44 might be enough strength for the portal hubs that are also being used.

The Dune Masters club (SoCal) has been using Thunderbird IRS components with success also. They run BIG motors, but don't have the driveline shock loads like dirt offroad...and limited travel..
I can see Thunderbird/Explorer and other 8.8 IRS holding up well to high power if travel is sufficiently limited. It has a very good track record of holding up in high power drag applications if you pay good attention to not shock loading it.

Lately I looked at the Mustang rear IRS because doing what I thought was easy...wasn't. What i saw in that system was a crutch link to prevent the arms from wrapping up like a dish rag when stopping. Their solution apparently works for them but wouldn't with our big heavy wheels and BIG brakes. I do know there are several aftermarket systems for the Mustang so maybe they saw the same issue ..or???
I don't understand.

Did you misspell clutch link, like a PTO slip clutch?

I get how you could pretzel an IRS by standing on the brakes. Inboarding the brakes so the 3rd and shafts are handling the torque would solve that (if they can survive a launch on pavement they can survive anything the brakes can do) but I don't see how a clutch of any sort helps.

Some beefed the centers maybe with 10" gears?
I know I sound like a broken record but a 9.75 center from an Expedition could be shoehorned into a Mustang with some creative brackets.

I actually considered sticking one in a Subaru wagon (because if you have to build a sub-frame from scratch why not go all out) until I remembered that I have mountains of D44 and Ford 8.8 stuff lying around and both would be massive overkill to begin with.
 

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I don't understand...


I think he might be talking about the integral link between the knuckle and the lower control arm...assuming he's talking a bout the new IRS stuff. It's a unique suspension setup for track control, but seems overly complicated for off road stuff, and doesn't cater well to much travel from the looks of it.
 

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I really dig your work, I like the way you're headed here.
On a side note, and I'm sure you've probably already looked into it after seeing all the work you've already done, but I think the Lincoln IRS can be made, on the most extreme end, to handle 12 or 14 inches of travel if I rember correctly. But that's on a bagged truck that Finnegan built on one of his YouTube videos, is that the same housing as the others in the 8.8 group internally..?
 

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Thanks for the help on the Mustang rear end. When I was really looking into it, and reported in (what I thought was) a technical article.... They did have problems with hub wrap, and that solved the issue without messing with the geometry. (Not double a-arm) AT SEMA a year ago, there were several sitting out with many modified. It is not a simple design and once I considered rotational strength with a 40" tire, I wasn't interested and started looking elsewhere.

As a fact: Most maintenance on a KOH IFS car is from stopping not accel. Always resisting that choppy torsional load..with CG moving forward. Heims started out as 7/8" now 1.25". Lower bushings started out as poly/poly, now poly with bronze thrust washers. Lower outer omni is 1.5", and the top omni has progressively gotten further away from the axle for more torsional rigidity (and some geometry benefit).

You might find the same on a Straight axle car, if you think about it.

Then you have to think about why 40 spline axles, and a whole car stops on 8 ea 3/8" caliper bolts. Kinda nuts...Maybe your foot comes off the brake faster than the gas.

Older CAD below shows top arm going over Omni requiring special "misalignments." Worse today...because RCV has done a lot of work.

All of this is for input only. Good additional info while progress continues. Sometimes we never know who gets helped...even by asking the right questions...and thinking. (Expedition)
 

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Discussion Starter #31 (Edited)
I just sent an email to DynaTrac about doing a 60... I've yet to hear back from them...
Your work looks great, and I'll be subbing this...
Nice.. Let me know how it turns out.. I contacted Dynatrac as well regarding the Dana 60 option and the Dana 80 option for an independent build. Both units were available inside of a week or two, but the price is crazy high. I think it was $3-5K each, depending on stub shafts and diff choice. The route I'm going is quite a bit more work, but much easier on the wallet.
 

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Thanks for the response, you're right about that being pricey..!
I imagine they're probably all getting set up for K.O.H. and that's why I hadn't heard back at this point...
And who would blame them..!
I'll be out there next year, just as a spectator though...
I spent quite a bit of time out in Johnson Valley camping back in my military days, it's an AWESOME place when K.O.H. moves in...
 

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Discussion Starter #33
Got some new parts in.. In an attempt to decrease the un-sprung mass at the knuckles, I have decided to go the pinion brake route. Got a new 14 bolt pinion flange, and retro-fitting dual piston calipers and rotors from a newer Ford F-150 (80% off clearance rack @ Summit Racing). Rotors are 13.78" diameter and 1.34" thick. Need to make a caliper mount plate that mounts to the pinion support. The last pic is not mine, just a pic of a similar setup.





 

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Hey CrCarson, can you post a pic up of your mounting plate when you get that hashed out..?
I'd appreciate it much, and thanks for being so detailed in your description, it helps a lot to see it in my head as I follow along.
 

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Discussion Starter #36
Hey CrCarson, can you post a pic up of your mounting plate when you get that hashed out..?
I'd appreciate it much, and thanks for being so detailed in your description, it helps a lot to see it in my head as I follow along.
Sure will.. I am hashing that out as we speak.
 

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Discussion Starter #37
What is your application again, front or rear? That will catch a lot of rocks won't it?
I am going independent front and rear suspension using 14 bolt housings. I will be tucking the housings up into the chassis as high as possible as to avoid contact with the terrain. Yes the larger rotors are a concern, but I might be able to get away with it by protecting it with some tubing. I am also running 46" tires so that will help as well.
 

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I am also running 46" tires so that will help as well.
That helps to explain a lot. 3" taller than competitive today. The good news is that you can make the front skid at a flatter angle. Too many people make it more vertical and frame hits during a G-out are HARD! A typical IFS in a G-out with tires and shocks loaded max, will only have about 3" of ground clearance to the frame skid. In the IFS world a 8-10" rock is a nuisance rock...until in the G-out mode. Then it is a ride in a helo. IFS cars (similar to SXS) are MADE to skid vs a SA which usually hangs up but doesn't have the G-out ground clearance problem.

Recreationally, it is less of a problem....but we always want to wick it up for a few miles .....

There should be a thread ...maybe by ThinAir a few years ago, were the talk goes to inboard brakes and the effect on anti-dive, etc. I don't remember any clear thinking on this but not totally interested either (technical). Jesse Haines (Mudtruck) made a IFS with inboards and portals, but was going to a customer to finish. We didn't hear anything back on that yet.

Personally. I like anti-dive, but it functions by locking up the suspension parts. Many drivers like to trail brake, so it screws up shock tuning. Recreationally not a big thing, but we are on the verge of active shocks which can stiffen on braking instead on locking suspensions. The thinking is less wheel hop allowing harder stopping. And realize the rear brakes also stop the front.....Linked together in 4wd...and death to xfer cases, etc.
 

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Discussion Starter #39 (Edited)
That helps to explain a lot. 3" taller than competitive today. The good news is that you can make the front skid at a flatter angle. Too many people make it more vertical and frame hits during a G-out are HARD! A typical IFS in a G-out with tires and shocks loaded max, will only have about 3" of ground clearance to the frame skid. In the IFS world a 8-10" rock is a nuisance rock...until in the G-out mode. Then it is a ride in a helo. IFS cars (similar to SXS) are MADE to skid vs a SA which usually hangs up but doesn't have the G-out ground clearance problem.

Recreationally, it is less of a problem....but we always want to wick it up for a few miles .....

There should be a thread ...maybe by ThinAir a few years ago, were the talk goes to inboard brakes and the effect on anti-dive, etc. I don't remember any clear thinking on this but not totally interested either (technical). Jesse Haines (Mudtruck) made a IFS with inboards and portals, but was going to a customer to finish. We didn't hear anything back on that yet.

Personally. I like anti-dive, but it functions by locking up the suspension parts. Many drivers like to trail brake, so it screws up shock tuning. Recreationally not a big thing, but we are on the verge of active shocks which can stiffen on braking instead on locking suspensions. The thinking is less wheel hop allowing harder stopping. And realize the rear brakes also stop the front.....Linked together in 4wd...and death to xfer cases, etc.
Yeah I know exactly what you are talking about. I assume when you say G-out, you are referring to grounding out, or bottoming out when landing and the suspension compresses. At that point, yes the chassis is physically much closer to the ground. To help alleviate this problem, and another problem relating to shock efficiency, I am going to have a significant positive caster angle on both the upper and lower A-Arms. Not just the knuckles, but tilting the articulation axis of the A-Arms back roughly 20-25 degrees. This helps keep the front/bottom of the chassis out of the dirt, and focus the dynamics of the terrain into the shock absorbers. For some reason I have not seen anyone do this as of yet in the rock bouncer/KOH world.
 

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Discussion Starter #40 (Edited)
Made a little progress with the pinion support today. Chucked it up in the lathe and machined a surface on the front face for the caliper mounting plate to bolt to. Hopefully will have the plates back next week from the water-jet shop so I can do a mock up assembly of the entire housing with brakes.
















 
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