Any Try To Put Independant Rear In F-body

[flashit]

Ok sound gay I know but just tore up another rear end and kinda sick of the pour handily of the solid rear end. My buddy has a Cobra and I have driven a few GTO's. They both hook super hard and handle way better. just wondering if any one has tried it or what not.

[INMY01TA]

It's been done once before. Seen the pics. I'll try to find em. Super exspensive tho.

[INMY01TA]

Found it: http://www.ls1tech.com/forums/showthread.php?t=539526

[JonB]

It's been done once before. Seen the pics. I'll try to find em. Super exspensive tho.

Found it: http://www.ls1tech.com/forums/showthread.php?t=539526

You beat me to it.

A 9in or a 12 bolt will be way stronger than an IRS. IRS are not known for there strength.

[C&Cbird]

Yeah, you really don't want to get in the middle of that mess.

[flashit]

Hey guys thanks for the info. My buddys Cobra rear end would have fit with almost no mods. But I said the hell with it and pushed it down the road. Got my self a spotless supper low mile GTO. Thanks agin.

[C&Cbird]

You do realize that most of the serious, high horsepower Cobra owners change out the IRS for a solid axle?

[flashit]

Yes I do know that, but his was almost new and I had a, for the most part, stock z28. There would not have been any problems with over powering it.

[ATCharming]

well it will handle around corners better but wont launch as well

[flashit]

True very true. our driving around this part is alot of back roads and runs for miles not just 1/4 mile. yes 1/4 is important but that just gets you to the first courner, then the real fun starts.

[JasonWW]

I was thinking of putting a 96-97 thunderbird IRS in my TA. I just bought a 97 Tbird and I was looking it over real good. I need to do some measuring, but so far it looks like it may fit. As far as cost goes, should be less than a new 12 bolt. You can buy an aluminum center section set up with 3.73 gears and a Traction Loc LSD for $600 brand new. The rest of the parts can be got at a junkyard or from a donor car. It uses the ford 8.8 which I believe is quite a bit stronger than the 10 bolts.

Anyway, I was planning on getting a new stronger axle, but if I could fit a stronger 8.8 along with IRS for less money and get a smoother ride as well, then why not?

Any info or comments are truly welcome.

[ApexVIII]

IRS gets a Sh*t load of wheel hope too! just do it right and be done.

get a 9" or 12 bolt

[JasonWW]

I believe there is no right or wrong when it come to modding cars.

As far as wheel hop, I'm not into drag racing.

Anyone know the strength of the 8.8 compared to the 10 bolt?

[Firebirdjones]

The 8.8 is very stout. In reality it's ford's copy of the 12 bolt chevy. The ford guys hate to hear that but it's the truth. They are so close in design it's scary.

They are nearly identical in ring gear diameter,,,,8.875 for the 12 bolt and 8.800 for the ford rearend. They are also both 30 spline axles and I believe even the pinion gears are the same diameter and spline count,,,,or very close.

It's basically just like a GM 12 bolt on the inside and setup the same way. Been a while since I have done an 8.8 but I do believe there are even a pair of bearings that interchange with the GM 12 bolts,,,,or a pair of seals,,,can't remember off the top of my head.

They are stout,,,and power some fast fords around these parts well into the 10 second zone no problem.


Our 7.5 inch 10 bolts in these Fbodies can break with just a 14 second car if you drive it hard enough.

[JasonWW]

That's excellent to hear. I plan to have about 500+ to the wheels so maybe this 8.8 will hold up. No drag racing, just street tires 19" so I should be fine.

Here's some more info I have on the Tbird rears.

a Ford 8.8 IRS such as in the 1999-up Cobra, 1989-97 Thunderbird/Cougar, 1993-98 Mark VIII? I just bought a 97 Tbird and was surprised it was IRS.

I know A arms and axles can be got at a slavage yard and Ford offers a brand new Aluminum center section already set up with 3.73 gears and Traction Lock LSD for about $600. Plus the 8.8 should be stronger than the 10 bolts. It's really got me thinking of a cheap IRS swap.

http://www.mn12performance.com/mn12-techinfo/traction-lok/traction-lok.htm

http://parts.factoryfive.com/newcatalog/chassis/irs.htm

I finally found some pics of the Tbird rear as it looks just dropped out of the car.

http://www.worldwidegarage.com/coppermine/albums/userpics/10151/141-4162_img.jpg
http://www.worldwidegarage.com/coppermine/albums/userpics/10151/141-4163_img.jpg

If you look closely you can see the 4 big round mounts at the 4 corners. Those hold the entire steel cradle which has all the arm attachments on it. The only other things that touch the body are the top shock mounts and the spring top. I'm sure all the suspension geometry can be altered with custom arms made from tubing and rod ends in the inner sides. You could probably keep the rubber bushings on the outer spindles just to soak up some harshness. It would be easy to replace those with rod ends as well. Since the cradle is steel the arm attachment points can be altered as well. Say you want 0 toe under both ride height limits. You can do that. You say you want 0 camber as well? Just make the upper and lower arms the same length.

[JasonWW]

So far I see people installing these under cobra replica cars, classic mustangs, custom pickup trucks, even a miata!

Here's some custom made arms.
http://www.mustangandfords.com/techarticles/mufp_0606_classic_ford_mustang_independent_rear_su spension_install/index.html
http://images.mustangandfords.com/techarticles/mufp_0606_03_z+classic_ford_mustang_independent_re ar_suspension_install+IRS_components.jpg

Here's a truck using the stock cradle and arms.
http://www.truckinweb.com/brandpages/chevy/0702tr_2004_chevrolet_silverado/index.html
http://images.truckinweb.com/features/0702tr_04_z+2004_chevrolet_silverado+air_ride_susp ension_bed.jpg
http://images.truckinweb.com/features/0702tr_02_z+2004_chevrolet_silverado+rear_passenge rs_side_view.jpg

I know the hubs can be drilled to accept the F-body rims because the Cobra guys do it for their 1/2 lugs.

If it will fit in a miata I bet it will fit in a f-body.

http://www.drivingenthusiast.net/sec-blog/images/2007/10/20/39db_3.jpg
http://www.drivingenthusiast.net/sec-blog/images/2007/03/14/486c_1.jpg

Surely this has got to be an easier swap than the C4.
http://img.photobucket.com/albums/v335/JasonWW/Misc%208/suspension20blue1b.jpg

[JasonWW]

So far I put my 97 Tbird and 99 TA up on lifts side by side and did a lot of measuring, comparing and picture taking.

I haven't uploaded any pics yet, but there is a lot of good news:

The track from rim to rim is almost identical.
The stock gas tank is fine as is.
With a few mods to the cradle mounts the floor pan of the F-body should not need to be cut in to.
The upper shock mounts can be used with the IRS shock location.

The only down sides are that:

the IRS sway bar is pretty wide and may rub fat tires, but I believe a new sway bar can be adapted.
I still don't know if the ABS reluctor wheels can be fitted. There is a chance on the 4 sensor cars, but I don't think so on the 3 sensor cars. This is still a mystery.

As far as the work needed to fit it:
The F-body spring pockets will need to be welded up which will add a lot of strength.
All the PHR sheetmetal on the passenger side will need to be removed.
There are several options as far as the brakes go so that's no big deal. Keep in mind the Ford unit uses a seperate mechanical caliper as a parking brake. So if you swap to a thicker rotor it may no longer fit.
The hubs can be redrilled, no problem.
As far as the actual 4 big mounts, the front two may need to be tweaked so they sit in the LCA/sway bar linkage area and don't touch the floor. New steel plates will need to be added up front and in the rear for the mounts.

Some have said that the rear of the car may be structurally weakend with this swap, but I don't see how. With the stock rear all the weight was on the spring pockets. Now the weight will be distributed through the front and rear round mounts. Now the front mounts are going to be stronger as they are closer to the front of the car, but the rear mounts are behind the spring pockets where it never supported much weight before. If you consider that the spring pockets will be welded over everything should be nice and strong, maybe even stronger than it was stock.

I'll try and have some pics up later.

[Firebirdjones]

I wasn't aware you were asking about strength of the independent rear. I was talking about the solid axle 8.8 rear.

As far as the independent rear goes,,,,I know they use the 8.8 center section which is plenty beefy enough,,,,but I don't think the half shafts would take alot of abuse. I haven't messed with the independent ford rearends,,,only first and second generation corvettes, which are notorious for snapping half shafts. Although I know on the vettes there is a company making bigger stronger half shafts for the vettes,,,,,with that in mind I would think someone is making stronger parts for the ford version as well,,,since there are so many high powered Cobra's running around with independent rearends.

With that said,,,I don't think you have to worry so much about the center section,,,,but I might worry about the half shafts, U-joints etc....that would be the weak link in that particular setup,,,,but wouldn't be hard to address.

Sure does look like an interesting swap,,,I would be interested to see more pics as you progress,,,,goodluck.

[Firebirdjones]

I would say what you are thinking about can be done,,,,sounds like your preliminary measurements show great potential.

A buddy of mine adapted an 85 corvette rearend in his tiny datsun 240Z.
We had to narrow the half shafts,,,,narrow the A-arms, actually we had to narrow about everything,,,lol....most everything was aluminum so it wasn't too bad to do,,,,but definately a complete custom job. It turned out slick and looks as though it's made for the car. If that could be done in this little car than the F-body should be no sweat ;)

[Jays00ss]

Way too much $ and effort for me. To each his own but man!!! I'll stick with my 9" and use the rest of the money for my cam and and the time I save putting it all in, I'll have enough time to make it to the track!!

[Firebirdjones]

Way too much $ and effort for me. To each his own but man!!! I'll stick with my 9" and use the rest of the money for my cam and and the time I save putting it all in, I'll have enough time to make it to the track!!

I hear ya,,,,but sometimes thats what it takes if you want to be unique and have an Fbody standout among a crowd, especially a 4th gen.

Personally I am a solid axle guy myself though, just like you.

[JasonWW]

Way too much $ and effort for me.
I think I can do this for less than the cost of a 9". I guess part of the expense is just the time and effort, but I like messing with this stuff. It's a challenge.

I have seen heavy duty halfshafts, they aren't any problem.

[JasonWW]

Some interesting info on the Cobra IRS.

http://www.miracerros.com/mustang/t_irs.jpg
If the pic doesn't load, copy and paste this into a new window.
miracerros.com/mustang/t_irs.jpg

Finally, there is the Mustang Cobra's independent rear suspension (IRS). Ford designed this IRS so that it attaches to the 1979-2004 Mustang's stock suspension mounting points. That somewhat compromised the performance of the IRS, but it means that the unit can be bolted into any late model Mustang chassis. The IRS subsystem is about 70 lbs. heavier than a solid rear axle, which contributes a better front/rear weight distribution, and it reduces the car's unsprung weight by about 125 lbs.

So they add some total weight to the car, but reduce unsprung weight a lot. Also note the mounts for the cradle. Those front mounts are what the Tbird cradle needs. If we bend them at a 90* angle and extend them it will clear the F-body floor pan and bolt right into the LCA mounts. Now that really is sweet. Much less modding to the car body.

A bigger pic that shows the common round suspension bushings on the ends of the cradle arms.
http://mysticcobra.net/system/00irs.jpg

We could also fab up some mounts like this:
http://www.seanhylandmotorsport.com/online/images/IRSsubframebracket.jpg
and then weld on the matching round bushing links on the back side of the cradle and the whole subframe assembly would bolt right in. This actually does seem to be the easiest way to mount it.

I also notice that some Mustang guys replace these round mount bushings with solid units.
http://www.seanhylandmotorsport.com/online/images/SHM-IRS-SUB.jpg

Solid aluminum suspension cage bushings to eliminate squirm found in the OEM rubber bushings. Complete the process of solid mounting the rear suspension for optimum handling at the track.

If we didn't really need need rubber bushing to isolate thae cradle from the car body it would simplify things even more. We could cut off the mounting arms, which would save weight and solidly bolt the unit to the F-body underside.

Maybe poly bushuings would be a good compromise?
http://www.seanhylandmotorsport.com/online/images/cobrairsbushings.jpg

Steeda IRS Subframe bushings improve handling, reduce wheel hop, and improve tire clearance on the 1999-2004 Mustang Cobra. The entire rear suspension of the Cobra is attached to a steel subframe, which in turn is attached to the car with just four rubber bushings. The rubber bushings deflect under load, leading to wheel hop and less predictable handling. Our polyurethane bushing kit substantially reduces unwanted subframe movement and wheel hop. You will notice an immediate improvement in car control after installing these bushings.