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MKVIII IRS fit question.

86GT2go

Active Member
Having read the threads (and using the search function here and on Google) in the MKVIII section of the forum and seeing the IRS mentioned quite a bit for the Factory Five cars but I have a few questions I would like to ask concerning the Fox chassis/Lincoln IRS.

Can the entire IRS set-up be swapped up under a Fox-Chassis car?

If not, what all needs to be changed to make it work?

If things do need to be changed, what and where would one source them?

Is it just the 8.8" carrier that can be swapped into a 99-04 Cobra set-up (as it is aluminum)?


I ask as i can get a good MKVIII running/driving for $800 and was wondering if the IRS can work in my 85LX Coupe as well. Thanks for putting up with a newbie and his questions.
 

86GT2go

Active Member
Never mind, just confirmed that the MKVIII WILL NOT fit back into a Fox. The only thing usable on it is the aluminum carrier. Looks like i might just pick the car up anyway for all the other usable parts, yank the center section, and go get an 03/04 Cobra IRS and swap the aluminum carrier in place of the iron unit.

I don't know if this thread would be worth keeping around, but if it is (as I am sure some other newb might read the MKVIII donor threads and think the same thing i did) feel free to keep it around.
 

ModFoxMustangs

Well-Known Member
Staff member
As the saying say there is no dumb question.. I will move this thread to the Mark 8 Section to help others... And thanks for researching this...
 

86GT2go

Active Member
Just wanted to make sure I (and others) got the right parts and a clear idea of what can/can't be used. I would have hated to buy the car for the rear, only to find I am S.O.L when it came time to swap it over!
 

Bill

Well-Known Member
Staff member
Donator
If you are going to put a Cobra IRS in your fox, the Mark VIII differential is the same as the 99 and 01 Cobra. It is a good part to save of the car, as you can rebuild it and change the gears to suit you without having a lot of down time. I have seen people change the dif when they go on a long trip to get better gears. It takes about 2 hours on your back or less on a lift. If you decide to do that, don't forget to keep the matching speedo gear with your spare dif. It takes 20 minutes or less to change once you done one or two and will keep you from getting that accidental speeding ticket.
 

86GT2go

Active Member
Thanks Bill. It is also interchangable with the 03/04 diff (or at least I have been told so by 3 different people). That would be quite handy indeed, to have several centers built up and be able to swap them out. I have several 8.8" ring and pinion/trac-lok set-ups here at the house, and to be able to just pull-and-plug would be cool! (then again, I would have to rebuild them as 31 spline versus their 28 spline configuration now).
 

86GT2go

Active Member
David,

Much thanks for that link. It will prove handy for sure. I just found a 99 Cobra IRS set-up that needs a rebuild, and a Lincoln MKVIII carrier (diff housing). I will be blending the two, along with a trip to the Maximum Motorsports catalog while it is out of the car!
 

David

Active Member
An IRS swap is fairly straight forward if using one out of another mustang. Full Tilt Boogie Racing offers a kit that you might be interested in.
 

86GT2go

Active Member
I know for my application, I will have to drill two holes (as my car does not have the mounts for quad-shocks) to mount the IRS, and will have to make the trans tunnel bracket that the parking brake cables attach to (that way I can even use the 99+ cables). I will have to also yank dual-exhaust hangers out of a wrecked 87-93 5.0L car and drill my frame to fit them (my car is an 85 Coupe 4cyl car).
 

David

Active Member
Sorry for all the multiple post...must be my internet connection...not too good offshore
 

86GT2go

Active Member
It isn't you, David, it has been the site/server all day. It was running quite slow and it double-posted me earlier as well.

Thanks for the link, I will tag it and use it when I do my swap-over!
 

86GT2go

Active Member
I remember them (Mouthbreather) doing quite a few articles on swapping newer components over into Fox chassis'. They were one of the sites I hit up when i first started getting into the Fox (them and foureyedpride).

You a Merchant Marine, Sailor, or Marine? Tug Captain or work a cruise ship? I spent some time afloat myself, so i know how connection can be (we were just getting internet aboard ship when I got out).
 

David

Active Member
I was in the Marine Corps at one time, but now I work offshore as a mechanic for saturation diving systems.
 

86GT2go

Active Member
Cool sounding job! I am an A&P Aircraft mechanic (right now, working in the CRJ200/CRJ700 platform on the CF34-3/CF34-8 GE engine family). Spent 4yrs in Uncle Sams Yaght Club as an AD.
 
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