Cobra Irs verus MM torque arm/ Pan hard bar (3 link)

JavorM1 · May 13, 2020

Question. Little long.

I currently have the MM 3 link torque arm/pan hard bar setup but have always wondered if the cobra IRS would be a better setup for general driving. I am not talking about drag racing or road course, but driving for the enjoyment and feeling less of the crap roads we drive on. I'm in Michigan so we have 2 seasons. Winter and road construction, so a quality ride for me is more Important. Who has made the change from a 3 link to IRS and why did you do it?

Wade_GT · May 14, 2020

I have a PHB on my GT and have driven an 03 Cobra for a couple of hours, so take my info for what (little) it's worth. The consensus suggests IRS is going to deliver better ride quality for daily driving. The advantage of the MM 3 link is lighter weight and lower maintenance. The straight axle is apparently 80 pounds lighter than the IRS system. The IRS is considered higher maintenance due to many bushings that (if not already) will need to be replaced. Further, there is the extra maintenance of the CV boots etc.

That said, the IRS is certainly desirable. It just depends on personal preference/willing to spend.

white95 · May 14, 2020

I’m not sure the 8.8/TA/PHB setup is light than an IRS ..

JavorM1 · May 14, 2020

I currently have the TA/PH setup in my car and driving on these Michigan roads can have it draw backs. Right now it drives good for the most part, but there is some vibration at higher rpm/speed that is transmitted thru the chassis. I have been looking to do the irs swap for a bit, but wanted some other options before I did it. I picked up an IRS and will be doing the swap over the winter. Hoping for a smoother ride and with the gear change to 3.55 will be a better drive.

JavorM1 · May 14, 2020

Plus I noticed with the 3 link setup, my tires are contacting the inside wheel wells when pulling in and out of driveways.

white95 · May 14, 2020

@lwarrior1016 has an IRS equipped ‘98 GT that has a nicely built, 4K rpm stalled 4R70w. His IRS has a plethora of upgraded bushings and lemme tell ya... It really transmits EVERYTHING into the car. You won’t be getting away from NVH with the IRS unless you leave all the rubber bushings in place.

CobraEd · May 15, 2020

JavorM1 said:
Question. Little long.

I currently have the MM 3 link torque arm/pan hard bar setup but have always wondered if the cobra IRS would be a better setup for general driving. I am not talking about drag racing or road course, but driving for the enjoyment and feeling less of the crap roads we drive on. I'm in Michigan so we have 2 seasons. Winter and road construction, so a quality ride for me is more Important. Who has made the change from a 3 link to IRS and why did you do it?

Bottom line: IRS does considerably better handling road irregularities. SRA tends to get more unsettled when encountering substantial bumps, pot holes. I live in northern ohio & spent lots of time driving on Detroit area roads so I understand what kind of roads you are dealing with.

I have and 85 GT & an 03 Cobra, neither of which are dailies, but I have driven both on the kind of roads you are talking about. The SRA 85 GT has the complete MM Road & Track Box which includes a panhard bar but not TA. Plan to add that later. The 03 Cobra has MM coilovers, a bunch of other MM stuff, & complete FTBR treatment. 400 in lb front; 650 in lb rear. Ride in the Cobra is not at all harsh & it handles rough roads very well. SRA of 85 GT (which does not have coil overs) gets significantly out of sort with major road irregularities.

I love the IRS in my 03 Cobra AFTER the FTBR upgrade. Before the upgrade with the stock rubber bushings (which were in excellent condition) I encountered unpredictable bump steer in rear which resulted in rear end kicking out in a 45 mph gradual 45 degree turn. After upgrade - extremely precise, predictable and stable in agressive cornering situations.

I'm assuming that cornering is important to you based on the equipment you have on your car. If you do decide to go IRS, don't do it UNLESS you either do the full MM or FTBR IRS upgrade.

JavorM1 · May 21, 2020

I ended up buying an IRS and just waiting for it to be shipped. It will need all new everything. Hoping to have it installed before the cold sets back in. Thanks for everyone's input.

BigBore96 · Jun 4, 2020

JavorM1 said:
I ended up buying an IRS and just waiting for it to be shipped. It will need all new everything. Hoping to have it installed before the cold sets back in. Thanks for everyone's input.

Let us know if you need any help with the install.

I've got an 04 IRS in my cobra and love it. I switched to it as my car had an non built 8.8 with 4.30s with griggs racing rear coilovers. Handled well but broke the 4.30s and the deal I found on this irs was cheaper than building the SRA once I realized I also had bad rear shocks.

Mine is running 90% of the full tilt bushings and it's very comfortable to drive. It doesnt transmit any more road noise than my stiff suspension SRA did. But NVH wise I'm probably not the best to ask as my car is loud, semi gutted, etc so it's not as smooth as a daily mustang anyway.

Handling wise it's better in the corners than my brothers griggs Watts link/TA sn95 setup just nowhere near as cool to explain what it is except to an alignment shop who will argue you only need a 2 wheel alignment.

At first it will feel way different under harder cornering or at least for me it did. It was what I'd call the standard SRA noodle feeling but with actual road grip.

Sent from my SM-N950U using Tapatalk

Wade_GT · Jun 5, 2020

JavorM1 said:
I ended up buying an IRS and just waiting for it to be shipped. It will need all new everything. Hoping to have it installed before the cold sets back in. Thanks for everyone's input.

Cool, send us pics of the progress once you get it.

JavorM1 · Jun 6, 2020

Currently it's in transit and I hope to see it this coming week. Normally I would have already ordered the bushing kit and had it already waiting, but decided to wait until it got here before I commited to ordering parts.

I do have a question about the pinion flange on the IRS. Will I need to purchase a 03/04 pinion flange or will the one on my aluminum drive shaft bolt up???

white95 · Jun 7, 2020

JavorM1 said:
Will I need to purchase a 03/04 pinion flange or will the one on my aluminum drive shaft bolt up???

If I remember correctly, and someone correct me if I’m wrong, the IRS has a large pattern flange but the SRA is smaller? Maybe this was for T56 swaps in SRA cars.. Hmm.. Anyway, I believe you need this for your current driveshaft and also a Moog 448 (1330/1350) u-joint.

https://www.dennysdriveshaft.com/p4...lange_yoke_fits_8.8_inch_rear_ends_large.html

lwarrior1016 · Jun 7, 2020

You can do that, or you can swap the pinion flange on the diff for the smaller pattern that’s coming out of your car.

white95 · Jun 7, 2020

lwarrior1016 said:
You can do that, or you can swap the pinion flange on the diff for the smaller pattern that’s coming out of your car.

Wouldn’t you have to reset the pinion bearing preload in doing so?

lwarrior1016 · Jun 7, 2020

white95 said:
Wouldn’t you have to reset the pinion bearing preload in doing so?

Yes, but if you leave the bearings and crush sleeve in place, you just have to re-tighten the flange nut just to where there is a little drag on it. Just make sure not to over tighten or leave it loose.

TrickVert · Jun 7, 2020

I'm interested to see how the install goes. I'm happy with the handling of my '95, but have run out of mods. IRS would be a cool project.

JavorM1 · Jun 8, 2020

I am planning on selling the current SRA with complete MM torque arm/panhard bad/ adjustable lower control arms to help offset the expense of the IRS. I will probably replace the flange and u-joint on my driveshaft.