IRS on a 97 GT

atlanticblue98 · Feb 11, 2009

if you currently have a v6, no cobra owner is going to trade your 2.73 geared 7.5'' open differential SRA. they would want an 8.8 from a GT

BruhBrahBrad · Feb 11, 2009

atlanticblue98 said:
if you currently have a v6, no cobra owner is going to trade your 2.73 geared 7.5'' open differential SRA. they would want an 8.8 from a GT

He said that he got a rear end out of an 03 gt

Goindeafonmtx · Feb 11, 2009

I'm doing the swap. Full bushings, coil overs, 4.30s. I started a thread in the "Build Up" forum.

It arguable to which is better. When actually researching this, you will find that the people have a bias towards what they are running. jmo. I'm part of the 99.99% of enthusists who drive their cars on the street and don't need an all out race car. Sure, there may be a difference among the two once you get to the upper echelon of competitive Mustang racing(and no one can say with absolute 100% certainty which setup gets the edge), but like I said, that is a very select group of people and cars. I'm sure that with my setup I'll do just fine.

Steven · Feb 11, 2009

To be different, the IRS is definately the way to go. I just like being able to launch the crap out my car and then take S curves. IRS's are much more expensive and involved to get it to do something of that sort

moose4130 · May 19, 2009

I have an 03 IRS in my car, and I thought it was the best thing I have done to it yet. I still drive it almost every day, or can, and the IRS rides great. I have Bilstein coilovers front and back, too, though. It handles much better than the stock stuff, and was fairly easy to put in. I did some of the bushings before I put it in, and some after, and would definitely recommend doing them out of the car. Overall, it is a great upgrade that you'll be happy with. It didn't take very long to do the actual swap and wasn't very difficult.

96saleen206 · May 29, 2009

I'm happy as heck with my IRS! I upgraded the bushings, have a differential brace, MM solid aluminum diff mounts, DSS Level 5 axles and am using Maximum Motorsports coilovers with the Bilsteins. So far at the dragstrip, I've done a 1.70 60' on 275 40-17 M/T Drag radials with the old Eaton and NOS setup 519 rwhp. Next week I'm headed to our local South Georgia Motorsports Park with some ET Streets and skinnies hoping I can hook my whipple at 19psi and a 50 shot and get into the 10's for the first time. Admittedly, my car is not setup for drag racing but the IRS seems to do alot of things very good. I would have stayed with the SRA but I had bought a whole 03 Cobra donor car and decided I'd try the IRS. Glad i did! The handling in combination with the MM K member, +3/4 A arms, and coilovers in the front is unbelieveable, even on bumpy corners the car never loses it's composure and it doesn't have that nasty "snap oversteer" that most SRA cars have from the control arms binding when its all hung out. It's one of the most predictable setups I've ever had. My only issue would be that the IRS is very tire sensitive to wheel hop. My current street setup is 295-30-19 Michelin Pilot sport 2's, and I do experience a slight hop on cold roads, but now that we're getting our normal south Georgia summer heat it just hooks and goes, and if it does spin it doesn't hop at all. With any drag radials it never hops cold or hot. One disadvantage is that the IRS swap will net you about 110# weight gain, but it does balance the car out more since its all over the rear wheels. Another advantage is increased wheel travel on lowered cars, I have yet to have it bottom out, yet every SRA car I've lowered has that constant issue, especially if you have a rear seat passenger. My vote would be to try it...You'll like it!

ReplicaR · May 29, 2009

You know, I've been road racing my mustang for slightly over 2 years now, and I have NEVER EVER have had this "nasty snap oversteer" that you speak of. I've ran the car stock, and on various different springs, and still no bind. Maybe because I did not overslam my car like most people do. My car also does not have any problems with rear traction over bumps either. I've ran Buttonwillow a few times, which is a bumpy track, and still had no issues, so unless you are racing over speed bumps, you'll be just fine, just like everyone else in Camaro Mustang Challenge and American Iron. The only time my car ever oversteers on me, is when the tires are cold, or my throttle input is rough.

Halfchrome · Jun 7, 2009

ReplicaR said:
You know, I've been road racing my mustang for slightly over 2 years now, and I have NEVER EVER have had this "nasty snap oversteer" that you speak of. I've ran the car stock, and on various different springs, and still no bind. Maybe because I did not overslam my car like most people do. My car also does not have any problems with rear traction over bumps either. I've ran Buttonwillow a few times, which is a bumpy track, and still had no issues, so unless you are racing over speed bumps, you'll be just fine, just like everyone else in Camaro Mustang Challenge and American Iron. The only time my car ever oversteers on me, is when the tires are cold, or my throttle input is rough.

The fact that you have never experienced the bind may be that your car is stock power wise or so your sig says, Im pretty sure it happens when alot of power or torque is used coming out of turns at higher speeds.

ReplicaR · Jun 7, 2009

Power level has absolutely nothing to do with bind. You can have 500 horsepower through a 4 link, and you can still put the power down just fine, if you don't transfer a lot of weight by being smooth at the wheel, and if you don't stab the throttle out of the corner, and apply the power smoothly like you're supposed to. The best suspension mod is seat time, and that's the honest truth.

STR33TR · Jun 12, 2009

"Another advantage is increased wheel travel on lowered cars, I have yet to have it bottom out, yet every SRA car I've lowered has that constant issue"

Anyone else confirm this?
I want to get as low as possible while maintaining as much ride comfort as possible. My car is never going to see a racetrack, except from the parking lot. IF I'M READING THIS RIGHT, the IRS swap and coilovers will let me keep more travel and ride quality while losing the most altitude?

ReplicaR · Jun 12, 2009

IRS is supposed to be more comfortable on the street and over the bumps, period. I don't know about travel, as I've never looked into it.

STR33TR · Jun 15, 2009

ReplicaR said:
IRS is supposed to be more comfortable on the street and over the bumps, period. I don't know about travel, as I've never looked into it.

And coilovers will give me the most drop while keeping the most comfort?
I'm weighing this against air bagging my SRA.

Goindeafonmtx · Jun 15, 2009

Depends on spring rate. With coilovers, you can adjust ride height regardless of spring rate. So comfort is in the spring rate. I run a 650lb spring in the rear on my IRS, so I don't really notice a difference in ride quality. But when comparing a stock sprung IRS to a solid axle car, the IRS is far superior in ride quality.

STR33TR · Jun 19, 2009

Goindeafonmtx said:
Depends on spring rate. With coilovers, you can adjust ride height regardless of spring rate. So comfort is in the spring rate. I run a 650lb spring in the rear on my IRS, so I don't really notice a difference in ride quality. But when comparing a stock sprung IRS to a solid axle car, the IRS is far superior in ride quality.

k. That makes sense. How soft a spring can you spec on a coilover kit? 650#s is really stiff, eh?

98bullet · Jul 12, 2009

ReplicaR said:
The best suspension mod is seat time, and that's the honest truth.

Thats the truth, The more you got the better you will be.

Steven · Jul 12, 2009

I do get alot of axle movement even with my Spherical LCA's and mostly new suspension. Axle snap is apparent, and it's one thing that I'm pretty annoyed with. It's the main reason I'm looking to do an IRS swap. I don't drag a whole lot, the cars a driver and corner carver. I've had a panhard setup. Worked fairly well but the fact when the car moves downward, the rod lengthens and pushes the axle over. Watts link is truelly the only source of exact and correct geometry in a solid axle application, however after watts link, control arms, springs, etc. it gets a bit expensive.

ReplicaR · Jul 12, 2009

Ok, first of all, Maximum Motorsports Panhard kit has a very long bar. Having a bar that is that long greatly reduces the axle shift through the motion right down the fraction of an inch. If you can't afford to lose that fraction, I think you might have bigger issues. There are plenty of people that are using Panhard setup for competition, even in AIX, and not one of them have problems with their setup.

Steven · Jul 12, 2009

Griggs and MM have proven it's usefulness. I know that, as I know griggs and maximum motorsports products fairly well. I am a bit of a perfectionist and in the back of my mind knowing it is not specifically correct geometry wise tends to irk me a little.

ReplicaR · Jul 12, 2009

If you are a perfectionist, I don't think you will ever enjoy a mustang. Stick axle will never have the indepence of the wheels like IRS does and the IRS will never have the traction of the stick axle. Time to get an M3

Steven · Jul 12, 2009

I wish. I want one, soon as I have the money I will get one. But in no way shape or form will my 95 GT go to make room for it. I have a dream, and that is to make a mustang a super car oneday. It's a big goal, and I don't know how feasible it is.