Beginers luck (not)

OKBODYMAN · #1 (**permalink**) 10-10-2011, 08:56 PM

I am the proud owner of a FFR mk4 kit. It was given to me as a gift from my employer for 30 yrs of service. Unfortunately i have allready hit my first snag. I purchased a 2003 mustang cobra IRS assy, only to find that it will not bolt right in. I never read anything in the assy manual indacateing that it would or would not work. Has anyone else ever made this mistake? If so, how did you fix it? My thought is to modify the frame, but i'm not sure? Any help would be appreciated.

bobcowan · #2 (**permalink**) 10-10-2011, 09:20 PM

No, the Mustang IRS is not a bolt in operation. It can be done with a few mods, though. The FFR kit is designed to use IRS parts from a Thunderbird Super Coupe. Thjose parts are similar to the mustang, but there are some important differances.

Is your kit set up for an IRS? If it is, the supporting frame work has been welded in. If it isn't, you'll need to get the kit from FFR and weld the frame in yourself.

Silverback51 · #3 (**permalink**) 10-11-2011, 03:38 AM

Damn, that a nice gift for 30 years. Congratulations. All I got was a watch.

You may want to also join the FFR forum. Lot's of guys there waiting to help you out.

G-Pete · #4 (**permalink**) 10-11-2011, 06:32 AM

The FF5 frame would take the IRS - with some modifications.
(this one here is a scratch build not an FF5)

You have to build a platform for the shocks, besides that I don't see any major problems. If you are interested in the adjustable upper shock mounts let me know.

Three Peaks · #5 (**permalink**) 10-11-2011, 06:54 AM

As stated above, the kit must be set up for the IRS with the optional mounting cage and control arms or you can weld in the necessary pieces that can be purchased from Factory Five.
Most of the Cobra IRS will work- the differential and axle CV's will work, but you will need to have axles shortened and the uprights/hubs will need to be from a Tbird Super coupe or Mark VII Lincoln with IRS. The hubs will need to be redrilled to 5 x 4.5 pattern.

The 2003 Cobra IRS rear and axles are much desired because of the 31 spline differential and matching axles. It is almost impossible to come up with the 31 spline CV axles without having very expensive custom units built.

This is all much easier than it sounds. Just tune into the ffcars.com forum and you'll be able to get all your build questions answered.

Bob