Swapping a 2015 Mustang Rear Into My 99 Mustang- Part 1

[@ajhartmanaero]

Hey everyone. Want to make a concise clear comment on why I chose this route. 1) part availabilty. 2) uniqueness of the swap. I'm well aware that an old IRS will basically bolt in but they are getting very hard to find, and at a reasonable price. Its a unique swap and allows me to do some cool videos and utilize my skills to make the swap happen. Much more fun than a bolt in deal.

[@the__black__box]

A mass produced swap kit would be a game changer for foxbody and SN95/New Edge guys. Best of luck with this project.

[@ajhartmanaero]

Thanks. Thought about it but not quite up my alley to produce a kit. To much going on with the carbon business.

[@the__black__box]

@@ajhartmanaero Hopefully someone will consider mass producing a swap kit.

[@young11984]

That IRS in a Fox you would have to put 12” flares on the car, not than im apposed to seeing it for performance application though.

[@2005StangMan]

Will definitely be keeping a close eye on this one. I've wanted to drop a Cobra IRS in my 04 street car, these IRS's would be muuuuch more accessible and have far more parts for upgrades and replacements.

[@carsonlomax7053]

If you run coilovers in the rear you could make a lower shock mount that sits in the lower spring perch but moves the shock mounting on-board to line up with the chassis.

[@jchack88]

Sounds like a great project. Its great to see fabricators take on projects that few else are willing to try. Get ready to make a kit version once you get the bugs worked out AJ, everyone is going to want one then. Beware of aftermarket camber links, there have been a lot of failures out there. Good luck!

[@drewbuckman]

I love the idea. I am in the middle of swapping a Cobra IRS into my track SN95. Parts for the Cobra IRS are getting hard to find. It would be great to run something like this that you can get parts for. I think it will work for a race car, not so much for a street car.

[@ajhartmanaero]

Yeah, one of the reasons I did this IRS was availability.

[@EscortSportage]

Cannot wait to hear your thoughts from straight axle to IRS, because this may be in my future.

[@ze_german2921]

I recently acquired a 97 Thunderbird with a 4.6 V8, It has a IRS from the factory and after driving it for a few days, I said to myself why did they stop making them, it drives like it is on rails.

[@idriwzrd]

I"ll be watching with interest. I'm doing the same thing (even with a '15 3.55 assembly) in our '01 budget endurance racer. The series we participate in, Lucky Dog racing, has very open rules, which makes it much easier. I'm not entirely sure how we're going to adjust to the extra three inches of track width yet.

[@jhidley1]

AJ, You're going from a 38mm rear caliper to a 45mm rear caliper and an 11.65" rotor to a 12.99" rotor. That is going to increase the rear brake bias by 38%. So if the car had a 70% front bias before it will now have a 59% front bias. Even with all of the downforce in the rear, you will need to do something to kill some of the rear brake. Run rear pads with a lower cf than the fronts, but the same temperature range. This assembly will probably add about 95lbs to the rear of the car, but it will reduce the unsprung weight by about 100lbs. You don't want to move the IRS rearward. Move it as far forward as possible. That will shift more weight off of the front tires and onto the rears. This will also put the wheelbase closer to stock, which may keep you out of problems with some rulesets. Don't move the shock mounts on the RLCAs inboard. This will just increase friction in the suspension. You are much better off tilting the shocks so that their upper mounts can meet the chassis. You are going to need a driveshaft with CV joints at both ends, or you are going to have to setup the front u-joint angle so its operating angle is less than 1 degree or optimally 0.5 degrees. Don't use any of the currently available aftermarket UCAs. Every one I've seen is junk and has no business being installed on a car. Guranteed to fail in a racing environment.

[@ajhartmanaero]

jhidley1 thanks jack. In real world I’m way ahead of this video. Rear brakes aren’t an issue since I have a prop valve. Driveshaft also not an issue. I did shove the irs forward as possible and gained a little wheel base. Not much tho. And shock mounts are utilizing the factory locations. Puts the shock at a little angle but not much.

[@young11984]

Agree, availability is plentiful and much cheaper than a 99-04 Cobra IRSs for sure. My only issue is availability for “street” bushings instead of heim style, i have an ‘18 irs in my F100 but welded the subframe in the chassis but all the voids in the bushing i knew would be an issue so Energy Suspension offers liquid polyurethane in various hardness to pour the voids full and to the outside edge of the oem shell so thats my go to for now

[@larrywarren1049]

Went looking for your f100 setup and couldn't find it

[@young11984]

@@larrywarren1049 i documented it on my FB dont have anything on here

[@NigelsModellingBench]

I just found your channel last week. It's awesome Dude!! Thanks!!

[@laltluangkimatluanga1763]

Yeah that solid Axel was so old technology that was the right way to go it can be improved more for a long term

[@dreed302]

Excited to see this one progressing.

[@kenerrico1919]

Love this content bro! Im looking for part 2 but the vids in the playlist are not in order. Any chance you could organize them first to last? I am absolutely going to follow you and do this to my 3 new edges so ill be watching them a lot and sharing with all the mustang peeps i drift with. Thanks Again Bro! Way to innovate!

[@georgef1176]

Super sick swap. I always figured 03/04 cobra would be the only way.

[@tiitsaul9036]

Interesting project. Hopefully turns out ok and makes the car faster.

[@noncog1]

If the rotors are a larger diam. you'll get a greater braking torque even with an equivalent piston area

[@p0intdk]

What about the diff, you going to put a real (clutch-plate)LSD in it? Kaaz makes one that is not to expensive for the Ford Mustang Super 8.8 diff. Maybe not now, but eventually.

[@ajhartmanaero]

DragonDragon maybe eventually

[@jhidley1]

This IRS already has a clutch type differential in it. For a real upgrade pull that out and install a torque biasing differential.

[@p0intdk]

@@jhidley1 A Trac-Lok is not adjustable as it doesnt have ramps, and it does not have as much potential for lockup as the Kaaz.

[@jhidley1]

@@p0intdk A trac-loc is adjustable in that you can adjust the preload on the clutches. I agree that this isn't good as the preload changes with clutch wear and the ramp angle in the differential is fixed. In any situation where you want the car to turn and to be able to apply as much forward thrust is possible, a differential that locks is going to have worse performance than one which can bias torque.

[@qbonpit]

I have questions

[@jonathontalley]

Still don’t see the benefits over the cobra IRS which is a bolt in application. Full tilt boogie racing has all parts needed for it.

[@ajhartmanaero]

Jonathon Talley that swap doesn’t get me excited. To easy to do.

[@johncreevy8966]

I'm doing a 2003 Cobra IRS swap into a 1986 Foxbody. The newer IRS assemblies are more plentiful, cost less and have a better design. I didnt go that route, as was mentioned in this video, AJ knew of zero that actually were completed successfully. I bought the FTBR bushings and other components for my 03 IRS and Bruce at FTBR mentioned that he has components available for the new IRS. I highly recommend his bushings for this project.

[@johncreevy8966]

fulltiltboogieracing.com/2016_GT350_and_GT350R_Suspension_Parts_and_Tools.htm

[@jonathontalley]

AJ Hartman Aero be sure to put a diff cooler on it.

[@ajhartmanaero]

@@jonathontalley I think I'll be ok to start. I'm at 330 hp in a 3000 lb car. Well below what the diff was originally designed for.

[@PhilthyHorseRacing]

Do you still need those OEM s550 measurements?

[@ajhartmanaero]

Chris Bouchard I’ll take them if you have them.

[@PhilthyHorseRacing]

@@ajhartmanaero in coming via fb messenger

[@johncreevy8966]

Where are you located? I have a 2015 Ecoboost that you can measure whatever you'd like to measure.

[@noncog1]

Positive camber*