Cobra IRS, 4-Link or Solid axle??
#1
Rotary Enthusiast
Thread Starter
Join Date: Jul 2002
Location: North Carolina
Posts: 863
Likes: 0
Received 0 Likes
on
0 Posts
Cobra IRS, 4-Link or Solid axle??
I have decided that I want to turn the LS1/FD into a strip car. Not a full out drag car, something I can still drive on the street but a more dedicated "drag" car. I am trying to decide what way I want to go in regards to the rearend.
Should I:
1. Cobra IRS- Already have the diff and cradle for it and it is basically a bolt in at this point. Problem is I am still limited by the IRS and the Cobra rear although much stronger than stock with better gear choices is still a "weaker" rear diff.
2. Ford 9" Solid axle- This I would have to fab something up to get it to work, not even sure how a solid axle would work in the car the way it is set up right now. This is a step up from the IRS but not very adjustable and still not bullett proof.
3. Art Morrison 4-link or similar- This is the ultimate setup for what I am looking for. Infinate adjustability, strong as hell and comes as a "weld in" unit. The problem I have here is can it fit? Will I still have some ground clearance? Should I just tub the car out while I am at it(which makes my NHRA rules more complicated)?
I cant decide where I want to go with this. It is still going to be a street car too but it is never going to go on a road course and going fast around turns doesnt do it for me that much so the IRS isnt critical.
I am strongly leaning towards the 4-Link or the solid axle but I am worried about welding it into the car and how well it will fit, then if I want to put more tire under the car. Decisions decisions.
Any input? Any one done anything similar?
Please if you dont have anything constructive to say please keep it out of this thread. No FLAMES!!!
Mike
Should I:
1. Cobra IRS- Already have the diff and cradle for it and it is basically a bolt in at this point. Problem is I am still limited by the IRS and the Cobra rear although much stronger than stock with better gear choices is still a "weaker" rear diff.
2. Ford 9" Solid axle- This I would have to fab something up to get it to work, not even sure how a solid axle would work in the car the way it is set up right now. This is a step up from the IRS but not very adjustable and still not bullett proof.
3. Art Morrison 4-link or similar- This is the ultimate setup for what I am looking for. Infinate adjustability, strong as hell and comes as a "weld in" unit. The problem I have here is can it fit? Will I still have some ground clearance? Should I just tub the car out while I am at it(which makes my NHRA rules more complicated)?
I cant decide where I want to go with this. It is still going to be a street car too but it is never going to go on a road course and going fast around turns doesnt do it for me that much so the IRS isnt critical.
I am strongly leaning towards the 4-Link or the solid axle but I am worried about welding it into the car and how well it will fit, then if I want to put more tire under the car. Decisions decisions.
Any input? Any one done anything similar?
Please if you dont have anything constructive to say please keep it out of this thread. No FLAMES!!!
Mike
#3
Full Member
If it were me personally, I would go with the Cobra IRS just to keep the car decent handling also. if you absolutely do not care and want just a drag car out of it, the 4 link setup would be ideal. It depends on your goals. Just another gutted strip car, just hack it and go 4 link with a solid axle- "high tech and modern" (since you have the LS1 Also- this is what i would do), go with the IRS and a 6 speed .
Joe
Joe
#4
Rotary Enthusiast
Thread Starter
Join Date: Jul 2002
Location: North Carolina
Posts: 863
Likes: 0
Received 0 Likes
on
0 Posts
The problem with the stocker is the gear selection, not to mention the strength. I need a lower gear than the 3.9's.
The high tech and modern crap is the stuff I would prefer to keep out of this thread. You all know all the guys you look up to.....Abel etc dont use the IRS rear so why hate on me. I still love the 7 just have to overcome it short comings in places I want it to shine.
The high tech and modern crap is the stuff I would prefer to keep out of this thread. You all know all the guys you look up to.....Abel etc dont use the IRS rear so why hate on me. I still love the 7 just have to overcome it short comings in places I want it to shine.
#5
Full Member
I meant no offense with the high tech comment. I do not know your goals with the car- 9 second drag car- go 9"/4 link. low 11 sec street cruiser that is nice to drive daily if needed, LS1/6 speed with IRS. That is what I am getting at. I was assuming using an LS1 that you were looking to do a modern setup, so I was just saying what would accent that nicely. Hell, you could put a tunnel ram on a stock 305 with glass packs and a 10 bolt open rear for all I care, I was just trying to be helpful and don't know the "theme" you are trying to follow with the car.
Joe
Joe
Trending Topics
#11
Super Snuggles
Originally Posted by LT1RX7
Should I:
1. Cobra IRS- Already have the diff and cradle for it and it is basically a bolt in at this point. Problem is I am still limited by the IRS and the Cobra rear although much stronger than stock with better gear choices is still a "weaker" rear diff.
1. Cobra IRS- Already have the diff and cradle for it and it is basically a bolt in at this point. Problem is I am still limited by the IRS and the Cobra rear although much stronger than stock with better gear choices is still a "weaker" rear diff.
Two things you have to remember are that the '03+ Cobra Mustangs weigh 800+ lbs. more than the FD, which puts a lot more load on the components when drag racing, and that Ford tried to give the car a "cushy" ride by suspending the rear subframe with an extra set of bushings. That's right, there are two "levels" of bushings; suspension component bushings and bushings which attach the rear subframe to the car.
Add to that the rubber bushings on the front and rear of the differential and it's no wonder that they have repeated complaints of drivetrain noise and lots of breakage claims from wheel hop, even on stock cars. My setup eliminates all that slop.
For occasional drag racing, you should be just fine. Keep in mind that these components are considerably stronger than any possible combination of FD parts, including the KAAZ differential and RP 300M axles.
2. Ford 9" Solid axle- This I would have to fab something up to get it to work, not even sure how a solid axle would work in the car the way it is set up right now. This is a step up from the IRS but not very adjustable and still not bullett proof.
3. Art Morrison 4-link or similar- This is the ultimate setup for what I am looking for. Infinate adjustability, strong as hell and comes as a "weld in" unit. The problem I have here is can it fit? Will I still have some ground clearance? Should I just tub the car out while I am at it(which makes my NHRA rules more complicated)?
You'd have to seriously modify the car to go this route. A good chassis shop would be able to do it, but you're talking about some invasive surgery to the rear of the car. Ground clearance won't be a problem, since they'll cut your floor pan to integrate the rails, but you'll be limited to running slicks all the time if you use a narrowed rear end and tub the car. If you go "street width" with the axle housing and don't tub the back of the car, then the widest tire you'd be able to run would be a 10.5 or 11.0" slick, but there's nothing wrong with that. Mustangs run 7s on them all day long.
I cant decide where I want to go with this. It is still going to be a street car too but it is never going to go on a road course and going fast around turns doesnt do it for me that much so the IRS isnt critical.
#12
Super Snuggles
Originally Posted by SPOautos
I dont think Hinson had any problems with the 3.9's
#13
Super Snuggles
Originally Posted by kwiktsi
go with the IRS and a 6 speed
#14
Full Member
Yeah, that's why I made the comment about not knowing what he wanted to do with the car- he said track and some street- to me that is a street car and would be an LS1 6 speed IRS car running low 11's to mid 10's and is awesome to drive daily too. If it is purely the ET, an A4 or even th 400 with a 9" would be the way to go. I was going to make the same comment about the cobra IRS and the weight difference between the stang and FD, but you beat me to it . I think the cobra IRS will hold up fine- especially if he uses an auto. I am all about drivers, not drag cars. I just got rid of a 396 stroker 94 Z that ran 10.3@136 on BFG drags- drove it to and from the track with the AC on the whole time and when I raced, it just sat in the pit lanes locked waiting for us to be called- no tinkering around and messing with it between runs- just drive there, do my thing and go home. That is what I consider a street car. If you back half it and go 9", 4 link, tubs, etc. it is just a drag car with plates on it .
Joe
Joe
Originally Posted by jimlab
This brings up an interesting point... If drag racing is your goal and not corners, then not only are you going to be quicker if you use an automatic transmission, but automatics are a lot easier on drivetrain components, even with a transbrake.
#16
Super Snuggles
Originally Posted by kwiktsi
also Jim- am I understanding right that you are running the Cobra IRS also? How involved was the swap?
https://www.rx7club.com/group-buy-center-69/03-cobra-8-8-irs-cradle-group-buy-313112/
#17
Do it right, do it once
iTrader: (30)
I was thinking the Cobra IRS would be the entire Independant Rear Suspension. It looks like when people refer to the Cobra IRS they are just speaking of the diff (axles and subframe changes too)...
Sounds like a good idea to me, I don't think putting the entire rear subframe would be a good idea, I think Ford made that rear suspension for the T-bird right? It doesn't seem any better than the Mazda rear suspension and is probably worse.
Sounds like a good idea to me, I don't think putting the entire rear subframe would be a good idea, I think Ford made that rear suspension for the T-bird right? It doesn't seem any better than the Mazda rear suspension and is probably worse.
#21
Do it right, do it once
iTrader: (30)
Originally Posted by jimlab
Look at the picture on the previous page.
Edit...
And big ugly coil springs, mounted in a wierd place.
Last edited by turbojeff; 08-26-04 at 09:49 PM.
#22
Full Member
I am going to go out on a limb here and say I *think* he meant to say "look at that pic in the thread I mentioned above". There is a pic of the setup- basically it is a modded FD subframe that has been modded to accept the cobra center section.
Joe
Joe
#23
Super Snuggles
Originally Posted by turbojeff
I did, I don't understand how that will show that it is better? Double bushings?
Edit...
And big ugly coil springs, mounted in a wierd place.
Edit...
And big ugly coil springs, mounted in a wierd place.
#24
Do it right, do it once
iTrader: (30)
Originally Posted by jimlab
Who said it was better? I was agreeing with you.
So for the record, when your referring to "Cobra IRS" your really just talking about the diff and associated bracketry.
I think the Cobra IRS (suspension, not diff) is a POS but I didn't want another battle.
If I were building a V8 FD I'd probably stick with the stock diff until it gave me troubles only if I wasn't planning on building a drag car. Then I'd probably go right for the Cobra diff.
#25
Super Snuggles
Originally Posted by turbojeff
So for the record, when your referring to "Cobra IRS" your really just talking about the diff and associated bracketry.
If I were building a V8 FD I'd probably stick with the stock diff until it gave me troubles only if I wasn't planning on building a drag car. Then I'd probably go right for the Cobra diff.
Even the 3.55 R&P in my case is a bit shorter than I wanted for 1st through 3rd, but I didn't want to give up any more gearing on the high end than I had to. In fact, with the 2.97:1 first gear of my M29 T56, the 3.55s are about the same as 4.10s behind a standard T56 (10.54:1 vs. 10.91:1).