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Independent Rear Suspension Forum » Info on lincoln rear swap to galaxie » 2/05/2014 12:22 am

JEM
Replies: 7

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I guess I haven't been around here lately.  

No time tonight, but yes I've been working on this, check some of my past threads around here and I'll try to comment more tomorrow sometime. 

John.

Independent Rear Suspension Forum » Innovative Ways To Update And Build » 9/15/2012 10:38 pm

JEM
Replies: 8

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Everything rigidly mounted.   All the NVH isolation gone.   Rubber-isolated diff mounting gone.  Suspension loads passed thru the rigidly-mounted diff case.

Basically street-rod C3/Jag practice, but design-wise a big step backward from how the MN12 Thunderbird was laid out by Ford.

IMO, of course...

Independent Rear Suspension Forum » Uh-Oh, am I over thinking things again?? What are your thoughts?? » 9/15/2012 5:36 pm

JEM
Replies: 16

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Double-cardan joints I think have rotational-speed limits, so do your calculations on what the driveshaft RPM will be at the max speed you want to be able to run.

Many cars these days use Rzeppa-type ball-and-cage CV joints in the driveshafts, BMWs typically have one at the rear for instance, the '08 GT500 shaft I've got in the shop has one BMW-type non-plunging CV at the rear and a big Porsche-axle-type plunging CV in the middle.

Independent Rear Suspension Forum » Jag IRS trailing arm location - S10 T5 transmission » 9/08/2012 10:30 am

JEM
Replies: 7

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jmbo wrote:

Instead of mounting to the frame would there be any reason I could not run the forward ends of the trailing arms to the mounting lug on the transmission?

You're talking about the lug on the bottom of the tailshaft housing?

The main function of the trailing arms - assuming either (a) you're using the Jag cage and something approximating original rubber cage mounts or (b) your diff is rubber-mounted - is to pass engine and brake torque loads into the car body.  If you run the arms to the transmission you'll be passing these loads into the tailshaft housing and the transmission (and engine) mounts. 

Might work fine, but I can't really judge in your application.

Independent Rear Suspension Forum » Newbie with JAG IRS waiting for installation » 9/06/2012 5:44 pm

JEM
Replies: 20

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303Radar wrote:

Frankenford, you might want to double check your rear end ratio.  Mine has a tag for 3.31 gears but the input turns three and a half time before the hubs have a complete revolution.  After I opened the diff cover, I saw the ratio on the ring gear was 3.54:1.  Also, Kugel Komponents http://www.kugelkomponents.com/ used to make/sell high density poly urethane bushings to replace the bearings on the control arms.  There might be some other companies as well.  Just letting you know you have options.

Why does anyone want to take out the bearings on the control arms?  They're a much more positive locating element than any sort of bushing would be, and that's a horrible, horrible place for polyurethane in any case.    There's a whole lot of applications for which the aftermarket sells urethane bits for which they're not at all suited - anything involving rotational motion, in particular.

I'm thinking, though, since I've got access to the CNC mill now, that I might as well go ahead and make a better mold for my urethane '64 Galaxie body mounts and maybe start selling 'em if I can figure out a proper way to vacuum degas them while they're curing, the set I made for my car had a 50% scrappage rate 'cause my de-gassing wasn't very good.

Independent Rear Suspension Forum » Lincoln LS suspension anyone? » 8/30/2012 11:55 pm

JEM
Replies: 2

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Used the diff, or the whole LS rear suspension assembly?

The rear suspension in those cars is an SLA design with the arms mounted at an oblique angle, it works quite well in the LS (and Jag S-type) but it's a funny looking thing...

I'm not sure what else uses that particular diff, there doesn't seem to be a lot available for it, Jag couldn't even be bothered to put a limited-slip in the S-type R.

Independent Rear Suspension Forum » MN12 Spider gears » 8/30/2012 11:51 pm

JEM
Replies: 3

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elgemcdlf wrote:

I have a Limited Slip carrier out of an Explorer which I understand are 31 spline axles. The MN12 is  28 spline. Does anyone know where I can get 28 spline spiders for the Limited Slip diff for the MN12?

Let me see if I understand what you're trying to do. 

You want to dismantle the Explorer limited-slip and swap the spider gears so you can run 28-spline inner drivers with it?

Hrmm.    I would have suggested just finding a 28-spline diff.    What year Exploder is that diff from?

28-spline Trac-loks are not hard to come by (I've got one sitting on the shelf, though I'm more or less hanging on to it for future use, now that my 31-spline Cobra axles showed up I won't be using it in the '64 wagon).

And if you're spending new money you can have an 8.8 Truetrac in 28 or 31-spline form for $400-ish.

Independent Rear Suspension Forum » Newbie Alert Why do Jag IRS's seem to be the most prevalent here? » 8/27/2012 10:54 pm

JEM
Replies: 18

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Ralphy wrote:

What type of material are Jag and CV type units made of?

Both the stock Jag and the first-gen CTS-V shafts are solid steel bars. 

Tubular halfshafts are less common, in part because of their bulk - C3/C4 'Vettes used basically short driveshafts for their axle shafts, and this is sometimes done on the early Jag IRS as well.

Tubular shafts in the late-model context - that is to say on one side of the vehicle for wheel-hop control - are generally I think mated to a splined solid stub at each end that mates to the CV.

Independent Rear Suspension Forum » Newbie Alert Why do Jag IRS's seem to be the most prevalent here? » 8/24/2012 9:03 pm

JEM
Replies: 18

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tyrellracing wrote:

The U-Pull it' Auto wrecking yards  here in Oregon are loaded with all kinds of IRS equipped cars. From Toyota Supra's,to Datsun Z's as well as  BMW;s of all types Ford T-bird's and Mustangs to name a few.

I chose to use the MN12 'Bird setup in my '64 Country Sedan largely because (a) it was the right width  (b) it was Ford and (c) the Thunderbird underbody and subframe mounting arrangement appeared to be fairly compatible with the old Galaxie frame. 

The downsides being that the subframe is bulky enough to push the gas tank out of its original location, it required a little surgery to get the front mounting legs where I needed them on the Galaxie frame rails (this was a case of six weeks to figure out what needed to be done and a day to do it...) and Ford being Ford a lot of parts are no longer available new from Ford. Fortunately, there's only a few things on the assembly that seem to wear particularly quickly, so I'm just making sure I collect three good used examples of everything for my spares inventory...

The only Mustangs that ever got IRS were the '98-04 Cobras, and mostly those get parted  before ever hitting the junkyards; going rate for a complete '03-04 Cobra IRS is around $1000.

A little junkyard snoopery hints that the '90s Toyota designs - including the MkIV Supra, but more commonly the Lexus GS and LS, which are dirt-common in the pick-n-pulls here now - are a straightforward but modern design, the total package is reasonably compact and mounting doesn't appear to be too troublesome.  If I were going to do something else I might look at one of those.

The E38 and E39 BMWs ('95-01 7-series/97-03 5-series) are starting to show up in the cheap yards now, and while their rear suspension is a very good design it's also designed for an underbody shape not typically found in old Detroit iron.   

The  E21/E30 3-series, E12/E28/E34 5-series and E32 7-series all use various flavors of semi-trailing arm rear suspension, which

Independent Rear Suspension Forum » Newbie Alert Why do Jag IRS's seem to be the most prevalent here? » 8/24/2012 2:13 pm

JEM
Replies: 18

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303Radar wrote:

With respect to preventing wheel hop, a Watts link/arm seems to be a good approach.  Lots of posts here with pics and explanations/setups.

Not really applicable with the CTSV multilink layout, I think.

Oh, and for what it's worth I just bought a pair of '03 Cobra shafts new from Tousley Ford at $325 apiece.

It's really a shame someone doesn't sell an OE-quality 31-spline inner driver and CV separately, since lots of folks either have good axles (SC, late Mark VIII) or wants to do something unusual.    Asking prices on used '03 Cobra shafts seem to be witihin 10-15% of Tousley's price new, so it didn't seem to make sense to chase used ones.

If I get wheel hop with the Cobra shafts I'll tear the right one down, swap in the center bar of the 'Bird 'fat shaft' and see if that helps.

Independent Rear Suspension Forum » T-Bird Half Shaft mods » 8/23/2012 11:33 pm

JEM
Replies: 8

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Ralphy wrote:

Just came across this info from the Factory Five FAQ.

http://www.ffcars.com/FAQ/irs.html

That came in handy today, as I'm sorting out what to do for axle shafts in the '64 and started dismantling a '91 'Bird manual transmission "fat shaft" to see if I can figure out how it was made. 

I've got one pair of '94 Lincoln shafts, one pair of '89 'Bird SC automatic shafts, and the aforementioned asymmetrical shaft.   All have the 28-spline inner drivers.

I can put together the old 'Bird 28-spline Trac-Lok and run some combination of the existing shafts, it'd really be too weak for the engine but it'd at least get the thing drivable that way.   Or I can bite the bullet and spend some money, get the 31-spline Truetrac and a set of '03 Cobra axles, which should be just about strong enough for most everything I plan to do with the car.   And if I did hit wheel hop with that combination (possible, but less likely with the automatic) then I could play with the asymmetrical shaft arrangement.

Independent Rear Suspension Forum » Newbie Alert Why do Jag IRS's seem to be the most prevalent here? » 8/23/2012 11:15 pm

JEM
Replies: 18

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Why the Jag?  It's been around fifty years, it's cheap and readily available, it packages into the same basic space as a stick axle, and the rod guys think they're purty if they're all polished up.   It is an interesting artifact of 1960s engineering, chock-full of stuff that no one would do like that now.

First-gen CTSV suspension - driven a few, works well, don't know a lot about the suspension layout.   GM's fix for wheel hop in the second-gen cars is asymmetrical halfshafts - one side is a typical solid bar, the other is fat and tubular, the result is that they wind-up at slightly different rates on launch and smooth the sharp spike of the forces being put into the mounts.  Seems to work very well.   

It's interesting to note, though, that Ford did the same thing on the Thunderbird SC from '89-93.  Only the manual transmission cars got the 'fat shaft'.  I've got one sitting on my bench right now, as I try to figure out what to do for axle shafts on my MN12-suspended '64 Galaxie wagon.

The aftermarket likes brute-force solutions  to wheel hop, in the CTSV, the '03-04 Mustang Cobra (in which, interestingly enough, Ford did NOT use asymmetrical shafts) - stiffer this, stronger that, harder everything else - I once drove a CTSV with a bunch of anti-wheel-hop stuff in it and it seemed to work but it really bodged the character of the car NVH-wise.

Independent Rear Suspension Forum » Started cutting metal... » 7/30/2012 2:06 pm

JEM
Replies: 14

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Progress!!!!

The modified MN12 IRS is hung on the frame now, it's bolted up under the car, and it's been sitting on its wheels.    A little bit of proof:

http://www.milleredp.com/~jem/galaxie/images/2012jul/irs_3.jpg


Modified MN12 subframe bolted up to '64 Country Sedan frame.  Front mounts and rear crossmember tacked in place.  Subframe bolted up using aluminum solid mounts I'd had made for setup purposes; when it's done I'll go back to the original steel-hat-with-rubber-insert mounts.   The crossmember had to be very thin vertically because the body floorpan hangs down between the frame rails at this point, the ends are a downward-pointing C-section that saddles over the mount bushings.   Fairly shallow (3/4in vertical ribs on the front/rear) but thick material (cut from 3x6x.250 steel) and ribbed on the underside around the mount bushings.  Maybe overkill, but...

The 8.8 pumpkin in this assembly is a scrap Mark VIII aluminum housing - the local pick-n-pull most often drains rear axles by punching a hole in 'em, and this one they managed not only to puncture the rear cover (about which I didn't care) but bugger one of the bearing caps in the process.   'Sokay, when it all goes together I'll be using the iron Thunderbird SC case anyway.

The pumpkin has an '02 Explorer rear cover (infintely more solid than the stock beercan-gauge early 8.8 rear cover) but the wings on the Explorer cover are too wide for a decent-sized isolator to clear the side rails of the subframe.  So the rest of the mount consists of a piece of C-channel bolted to the Explorer cover wings, and a pair of E38/E39 BMW rear diff mount bushings pressed into a fabricated steel mount assembly that bolts to the subframe.   We'll see how it all works out.

The '02 Explorer rearend assembly is an 8.8 and much beefier overall than the earlier units but very different in shape and critical dimensions; the axle shafts, side bearings, etc. are all different and it would not have been easy to a

Independent Rear Suspension Forum » T-Bird Half Shaft mods » 7/30/2012 1:56 pm

JEM
Replies: 8

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PaulProe wrote:

I put this into place and my bottoming issues dis-appeared. but the nagging question, is am I setting myself up for future problems? How does one know the amount of load placed on the retainer rings and spline ends when the vehicle is moving.

Yes, there will be some loading, but I think you're on the right track.  Worst case I'd think you need thicker snap-rings or a spring-washer to preload the whole thing.

Independent Rear Suspension Forum » Jaguar IRS trailing arms - how important are they? » 7/30/2012 1:50 pm

JEM
Replies: 4

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On the early XJ rear the trailing arms are there to take acceleration/brake torque loads off the cage mounts (they can't handle it) and to 'steer' the cage and induce roll understeer.

The later design gets rid of them entirely, the new mount design is much more solid and spreads the loads further and roll understeer is a function of the revised pivot angles of the lower arms.

The later design also removes the vehicle weight from the cage and its mounts, it has a single long coilover assembly that mounts directly in the upper fender structure - something typical of modern IRS designs e.g. BMW.

Independent Rear Suspension Forum » 460/C6/MN12 & wheel stands » 7/30/2012 1:41 pm

JEM
Replies: 6

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Well, you're running a 460 and a C6?

I'll be running a 525ci stroked 460 and a built 4R70W.

I've been advised by people whose opinions I trust on this that I'll probably bust the diff, if I fix that without beefing the axles I'll bust them next, once they're fixed I might bust the transmission.

So...if you want to do what you're planning to do, you're going to need to talk to someone like DSS who makes the axles and 35-spline hubs for that segment of the dragstrip '03-04 Cobra community who hasn't switched to a stick axle.

Me, I'll be gentle for now, as I have lots of other things to spend money on before I go throwing another $2500 at the rearend.

Independent Rear Suspension Forum » Mark VIII to a 1971 mustang » 3/16/2012 4:22 pm

JEM
Replies: 4

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Pastorpat wrote:

I did some measuring and the with of the front spring perches is 40 inches.  Each perch is 3 inches wide.  The subframe rail mounts on the inside of the front spring perches, then it gets wider until it reaches the rear of the carn.  The front of the Mark VIII mounts are 41 inches wide so i dont think that will be to hard to make weld up brackets for.   The Gas tank does seem to be the issue.   I will need to cut down the mark viii cage.  More details to come and some photos.

My biggest concern there is that while the front subframe legs are the proper distance apart, they slope downward to get there; in order to readily mount the stock pads under the Mustang spring hangers you won't be able to get the axle and suspension tucked up enough under the car.

I may be wrong, but I'm guessing that to get the whole thing far enough up under the car you'll have to cut off at least the front mounting legs and fabricate new ones out of 2.5in x .125 steel tubing to extend down and under the frame rails.

Just a guess.

Independent Rear Suspension Forum » Name That Part! » 3/16/2012 4:05 pm

JEM
Replies: 11

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The AU Falcon IRS is a bit reminiscent of an improved MN12 Thunderbird IRS.

Independent Rear Suspension Forum » Mark VIII to a 1971 mustang » 3/14/2012 12:56 pm

JEM
Replies: 4

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Pastorpat wrote:

My son and I are looking to place a 1996 mark viii IRS in a 1971 mustang.  Wondering if anyone has seen it done.

Not in a Mustang.

I'm putting one in a '64 Galaxie (actually Country Sedan wagon) and I've known folks who have put them in F-100s as you've noted.

The MN12 'Bird/FN10 Mark rear suspension is pretty wide.  If I remember correctly your stock axle is 60.25 over the flanges.  My wagon's rearend was an inch wider than that, and I still had to have my rear wheels made with an extra inch of offset to accommodate the rear.    You might get away with it.  I think - have not tried it - the subframe could be narrowed maybe 2in in the center, where the diff mounts.   

The MN12 subframe is quite bulky and heavy (80lb or so for the bare subframe - the early SC subframes have more reinforcement inside, Marks and other 'Birds did not get this.)   Mine is not a bolt-in; I put pie-shaped cuts in the front legs of the subframe to narrow them 2in, lower them 2in, and move them back 1/2in which more or less centers the mount bushings on the frame rail just behind the point at which the rails kick up to go over the axle - I'm fabricating weld-on mounts for the frame rails at that point.  The rears barely fit between the frame rails; I'm fabricating a new welded-in crossmember to pick those up.  I'll also have to deal with the gas tank, which won't fit in the stock location due to the subframe and sway-bar location.

The '98-03 Cobra IRS might be a closer fit, it should be just about exactly the right width, the tubular subframe is less bulky, and the mounts would be easier to adapt.  They're more expensive on the used market but I think they're all 3.55s and Trac-Lok whereas only the SC 'Birds got 3.27 Trac-Lok gears and all the Marks were crappy 3.07 open diffs.

Pics a little later, have to run right now.

Independent Rear Suspension Forum » The Jaguar IRS picture thread » 1/31/2012 1:14 pm

JEM
Replies: 159

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Digz wrote:

And I'm curious as to how they hold it off the ground.

Don't you see the wood blocks?  ;)

Could be they used a coilover or something to the trailing-arm pickup, the arms have been shorn of their normal lower shock-mounts but the trailing-arm mount is still there.

Independent Rear Suspension Forum » The Ford IRS picture thread » 1/25/2012 1:06 pm

JEM
Replies: 44

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The real impact of rear roll-oversteer is what it does to the steering, and any significant amount of rear roll-oversteer is going to make the car twitchy.

Independent Rear Suspension Forum » The Jaguar IRS picture thread » 1/17/2012 1:18 pm

JEM
Replies: 159

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Ralphy wrote:

I just noticed he went so narrow, the top shock mount is outside the lower. WOW!

There's that, and I'm wondering just what he thinks he gets from carrying that much rear rubber, and running double spring/shock coilovers in a car that small and light with arms that short is just a complete waste IMO, but the real problem...how's the effin' diff mounted?

Let's review how the diff's mounted in an XJ - it's rigidly mounted to the cage at the top and the bottom.  The cage is then mounted to the car through rubber bushings at the outer ends (nice long lateral lever 'tween diff and cage ends) and acceleration/braking torque is passed through the lower arms to the trailing arms to the body.  The cage mounts also carry the vehicle weight 'cause the coilovers mount to the cage.

In the XJ40 Jag took off the trailing arms, and revised the diff mounting, it now sits on a cradle that mounts to the body with two fairly widely-spaced rubber mounts in the rear and two large and widely-spaced mounts up front.  Further, these now handle only fore/aft and lateral loads - the vehicle weight is now passed up to the fender structure, not through the diff mount.

His design has the diff carried by a couple bushings at the top.  Solid (noise) or rubber (flex)?  Can't tell.  His 'front pinion mounts' are little rod-end things that go straight up and down - yeah, they'll keep the nose of the diff from bobbing up and down, but they won't provide too much help in keeping it from moving front/rear.   I see no other support for the bottom of the diff. 

I'm fairly confident that no matter what his upper diff mount looks like it's going to move around enough for this to matter, even if it's solid it'll still twist everything a bit if he's got any torque at all. 

So acceleration/braking loads are going to go through his lower radius rods - it's going to push straight forward on them under acceleration and pull straight back on them under braking.   That's what the stock

Independent Rear Suspension Forum » Designed To Bind » 1/16/2012 9:25 am

JEM
Replies: 90

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Ralphy wrote:

The lower forward link adds some roll steer.

I don't see anything from the picture that would indicate that.

Independent Rear Suspension Forum » The Jaguar IRS picture thread » 1/16/2012 12:44 am

JEM
Replies: 159

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Ralphy wrote:

Jaguar IRS in a Datsun 510
WOW, NARROW!

Even if you accept the premise of the big giant rear meat being tucked in so far, I see a lot I'd have done very differently.

Independent Rear Suspension Forum » The Ford IRS picture thread » 1/14/2012 10:31 pm

JEM
Replies: 44

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Ralphy wrote:

Lincoln Mark VIII Bagged IRS

That appears to use the Thunderbird/Mark VIII uprights (so does the Factory Five rear and the Hurricane one pictured) and diff pumpkin but all the rest is fabricated.    Maybe they borrowed some of the geometry but, given the layout of that upper arm, I'm betting it's not too similar.

Independent Rear Suspension Forum » All You Jag Guys, Bend Your Bones! » 1/14/2012 10:22 pm

JEM
Replies: 1

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I don't understand what you're saying.

The trailing arms do not bend the LCAs. 

The trailing arms provide two functions - they provide a load path into the body for acceleration and braking loads (something the cage mounts cannot do) and they provide roll understeer by skewing the entire cage assembly on its mounts slightly.

The LCAs are rigid, their inner pivots are a roller bearing, and the pumpkin is rigidly mounted to the cage; the cage is flexibly (perhaps too flexibly) mounted to the car.  The trailing arms do not bend the LCAs, they move the entire cage.   

The XJ40 did away with the trailing arms because it had a far better-supported mounting subframe and revised geometry of the LCA pivots provided roll-steer and anti-dive, so they were no longer needed.

The other factor of course is that the early Jag cage and its mounts also carries the vehicle weight.  The XJ40 rear suspension mounts do not carry the vehicle weight, that's transferred through the spring/shock assemblies into the upper fender.   This is more typical of modern IRS designs where the spring load is passed directly to the body and not to whatever carrier or subframe the suspension mounts to.

Independent Rear Suspension Forum » Jag IRS lesson learned » 1/14/2012 1:49 pm

JEM
Replies: 1

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So I got a new battery for the Sawzall and was back at the pick-n-pull for half-price day, and the Capri I was there to scrounge some Cortina parts from had been sent to the crusher.

Bah.

So I went off in search of the '77 XJS I'd seen the last time I'd been out there, to try an experiment.

Someone had already been wrenching on one side, the exhaust was gone on that side and one of the cage mounts had been unbolted.

Attempt to unbolt driveshaft, bolts too tight for my poor selection of box wrenches, note it's a one-piece shaft (it was an SBC conversion, not sure if the one-piece shaft is normal on an XJS) and decide to see if I can wrestle the thing off the slip-yoke once the cage is down - 3 min.

Pull the retainer and vertical bolt out of the front of the trailing arms - 1 min per side.
Arms won't come off (naturally) so sawzall the cone off the floorpan - 2 min per side. 
Sawzall the remaining exhaust behind the cage - 2 min.
Unbolt the sway bar from the floorpan - 5 min per side.
Sawzall the remaining cage mounts - 2 min each.

IRS falls to the ground.
Cut brake line and parking brake cable. 

Total time to this point right around 30 minutes.   Much quicker than wrestling with unbolting the cage mounts, trying to break the trailing-arm mounts loose from the floorpan or unbolt them from the LCAs, and the whole thing comes out completely intact.

Note - one of the cage mounts separated while I was sawing it, and I've seen others separated on junkyard cars - try not to put body parts under the cage while working on the car, if you do have to do work under the car e.g. driveshaft leave the trailing-arm bolts (and sway bar, if so equipped) until you're done under the car. 

I was working alone and this was more of an experiment than anything else so when I couldn't budge the thing from under the car by myself I abandoned it.   Looks to be a 3.07, by the books it should be an LSD but I can't confirm as I couldn't get the brakes loose enough to turn the hubs.

Independent Rear Suspension Forum » New here. Working on BMW IRS » 12/28/2011 7:05 pm

JEM
Replies: 15

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Ah, E39 subframe, got two of 'em...

Didn't want to spend 1500 for a Quaife?

Have you seen the 02 Explorer rear cover?  The Explorer pumpkin mounts like the E38/E39 diff, one offset front and two widely spaced in back.  Maybe too wide for the BMW mounts.  Have one I'm using in my MN12 setup (making a mount for it that uses...E39 BMW bushings...) and could take some measurements if you can tell me what you need (can't get the M5 or 540 on the lift right now...)

Think I'd make a bracket to retain the BMW offset front mount, they're not known for breakage, what makes you think the diff is moving around too much?    I'm using 4-point mounting on the MN12 setup in the Galaxie (unless I decide to leave out one bolt...) 

As is typical for Ford, the stock FN10/MN12 front mount bushings are NLA from Ford,  and I don't want aftermarket urethane.  I may end up using the '03-04 Cobra front bushings (still available from Ford, $28 each for the top and close to $90(!) each for the bottom half.)

C4 and Jag comparisons aren't applicable here 'cause no suspension or braking loads go thru the diff mounts.

Independent Rear Suspension Forum » This Pic Tells Me A Lot! » 12/04/2011 10:38 pm

JEM
Replies: 5

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Ralphy wrote:

Gotcha. so the 8.8 uses a toe rod with one upper and one lower mounting point  at the hub? Then the 7.5 uses one upper mount and two lower mounting points at the hub?

Uh...no, not quite.

7.5 and 8.8 just refer to two different final drive designs. 

The 7.5 in stick-axle form was used in a bunch of different Fords - Mustangs, Rangers, etc.  IRS versions were used in the non-SC MN12 Thunderbirds and I believe the DEW98 Lincoln LS/Boringbird/Jag S-type also uses a 7.5 (might be wrong.)  The MN12 application is an iron case with two narrowly-spaced mounts on either side of the pinion snout and one V-block mount bolted to and cantilevered out behind the rear cover; I believe the DEW98 case is aluminum, and the mountings are certainly different and more typical of, say, BMW practice with one offset front mount and a pair of widely-spaced mounts in back.   I believe Ford's also had a 7.5-in ring gear axle in some of their (other-than-Jag) European products but I can't say whether it has anything in common with this one.

The 8.8's also been used all over the Ford product spectrum as a stick axle from Crown Vics and F-150s to Explorers and Mustangs.  The first IRS application was the '89 MN12 Thunderbird SC/Cougar XR7 and the FN10 Lincoln Mark VIII; it was subsequently used in the '99-04 Mustang Cobra and '02-09 Explorer.   The 'Bird SC case was iron, the Mark VIII and the Cobra shared an aluminum case design; both mounted as noted with the 'Bird 7.5 above.   The aluminum cases are not known for breakage, but the mounting arrangement and especially the thin aluminum rear cover ( used even on the iron 'Bird cases) are notorious weak spots.   The '02 Explorer unit is far beefier, a much stouter and heavier case with a very strong ribbed rear cover.   The Explorer assembly also uses a mounting arrangement similar to the LS, with a single offset mount forward and a pair of widely-spaced bushings in back.   

Just about everything about the Explorer u

Independent Rear Suspension Forum » Miata conversion - 7.5" Ford » 12/02/2011 10:47 pm

JEM
Replies: 21

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tool_man wrote:

Ralphy,

I've been there a bunch, asking opinions and getting ready. I've seen the post. They're working with an 8.8 which is reported to be more problematic than the 7.5.

Problematic in terms of making it fit? 

I'd meant to get you a bunch of pictures and dimensions of an MN12 knuckle, but right now I'm spending my spare time (a) dragging the frame back out from under the '64 wagon and (b) moving my project writeups onto an externally-hosted Wordpress site so it won't be such a pain to maintain the things and I'll be able to write on them all in one place.

Hopefully over the weekend now I'll get to come up for air...oh, wait, we're going to see the Nutcracker on Sunday...we'll see.

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