SRA build?

[TRQJUNKIE]

Looking to do a SRA build here soon and looking for opinions for it. On my list for this build are moser axles, and MM lower control arms. I was thinking about a detroit locker for a diff but not sure if it is the best for drivability. I am also thinking about a MM torque arm. I am looking to get strength and good handling.

What will i need to ensure the traction control will work and I want to eliminate the use of c-clips. Sorry for the million questions im just a noob at the SRA game.

 

[SlowSVT]

For a minute I thought you said you wanted "great handling" but then I noted the title of the thread and re-read your post where it said you wanted "good handling".

Makes sense to me.

 

[Digital]

Looking to do a SRA build here soon and looking for opinions for it. On my list for this build are moser axles, and MM lower control arms. I was thinking about a detroit locker for a diff but not sure if it is the best for drivability. I am also thinking about a MM torque arm. I am looking to get strength and good handling.

What will i need to ensure the traction control will work and I want to eliminate the use of c-clips. Sorry for the million questions im just a noob at the SRA game.

My rear is in my sig. You want a really nice adjustable control arm so you can set it. Brand doesn't really matter long as you get the bushing type you want (poly) and they have good adjustment. Lake wood makes a really nice 50/50 shock and then the spring is going to be up to you for ride height but the softer the better.
I would go with a eaton posi or a 03/04 / GT500 diff (almost the exact same unit) rebuilt with clutches and shimmed. Those things are damn near bullet proof.
Moser 31s can't go wrong. 33s max out a 8.8 but it's harder to find a diff to fit 33s and the axles are more expensive.
The Ford Racing gears have gotten a lot better in the last couple of years and they are very quiet.
Weld your axle tubes, get some SS brake lines and good pads. Don't bother with a diff cover (unless you like bling), just fill it with good fluid (royal/redline) and let it ride out.
Also if you're making decent power invest in battle boxes or take it to a good welder and have him weld you new plates to mount your upper control arms to. You will pull them free eventually and tear the welds loose.

For a minute I thought you said you wanted "great handling" but then I noted the title of the thread and re-read your post where it said you wanted "good handling".

Makes sense to me.

Easy easy, lol. You're just hatin cuz he has lvl 5s =P

 

[stal94gt]

detroit tru track is a great diff for the street. be sure to use spherical rod ends for the lower control arms. polly bushings will tear tour torque boxes up because they dont allow for articulation.

 

[SlowSVT]

My rear is in my sig. You want a really nice adjustable control arm so you can set it. Brand doesn't really matter long as you get the bushing type you want (poly) and they have good adjustment. Lake wood makes a really nice 50/50 shock and then the spring is going to be up to you for ride height but the softer the better.
I would go with a eaton posi or a 03/04 / GT500 diff (almost the exact same unit) rebuilt with clutches and shimmed. Those things are damn near bullet proof.
Moser 31s can't go wrong. 33s max out a 8.8 but it's harder to find a diff to fit 33s and the axles are more expensive.
The Ford Racing gears have gotten a lot better in the last couple of years and they are very quiet.
Weld your axle tubes, get some SS brake lines and good pads. Don't bother with a diff cover (unless you like bling), just fill it with good fluid (royal/redline) and let it ride out.
Also if you're making decent power invest in battle boxes or take it to a good welder and have him weld you new plates to mount your upper control arms to. You will pull them free eventually and tear the welds loose.


Easy easy, lol. You're just hatin cuz he has lvl 5s =P

Where have you been? You're late! :-D

Looks like our friend want's to build himself a dragster.

Level 5's :nonono:

 

[BO TY KLR]

I'm going solid as well. Strange makes a nice c-clip eliminator setup for rear disk with antilock

 

[TRQJUNKIE]

Thanks for the input guys. SlowSVT try helping instead of bashing:kaboom:

Anyone try MM's Torque arm instead of using the normal upper control arms?

 

[P49Y-CY]

I'm going solid as well. Strange makes a nice c-clip eliminator setup for rear disk with antilock

those look real nice :thumbsup:

 

[SlowSVT]

SlowSVT try helping instead of bashing:kaboom:

I don't recall me "bashing" anyone here. You may not realize this but I always try to make people understand what the implications are of doing this conversion. You would be surprised by the number of people who actually think this is an upgrade to the cars rear suspension and after they realize this is not a good directions for most people. It's your car not mine but it's sad to see another Cobra loose it's IRS :nonono:

 

[TRQJUNKIE]

Where have you been? You're late! :-D

Looks like our friend want's to build himself a dragster.

Level 5's :nonono:

Not exactly words of help here. All I'm going to say is Ford stopped putting in the IRS for a reason.

Anyway, anyone have experience with the swap and tips for me

 

[stal94gt]

i just did the swap my self, i will say this you will need a budy to help you move the irs out since the thing is heavy as hell. dont for get the drive shaft flange is diff on the gt and the cobra's. i used a percision 448 u-joint to swap the gt flange onto the cobra drive shaft. the swap was easy for me since i pulled the rear out of my own gt and put it in my cobra so i had everything. of course you will have to swap cat backs, and bump stop. i kept the cobra rotors since they are thicker. i need to rent a brake caliper compressor from auto zone since the rear brake calipers have to be rotated in. the irs is a easy to pull it is only 4 bolts, 2 bolts where the lower control arms on a gt hook up, and 2 where the quad shock bracket would be on a gt.

 

[SlowSVT]

Not exactly words of help here. All I'm going to say is Ford stopped putting in the IRS for a reason.
Anyway, anyone have experience with the swap and tips for me

Your response was kinda what I was expecting and it's not surprising. The reason Ford did not equip the new Mustang was mainly for cost reasons and the GT500 was a bit on the porky side to begin with. There was some dismay in the Mustang community and the automotive press why Ford chose not to equip the GT500 with an IRS.

If you want to convert your Cobra to an SRA for personal reason and you care more about saving 125 lbs off the rear end, simplifying the rear suspension and adding a degree reliability then there is nothing wrong with that. A solid axle is cheaper and easier to repair and are very plentiful.

If handling is important to you then a solid rear axle is a wrong move and you are about to downgrade the cars cornering ability which is what the Cobra is designed to do and hurt it's re-sale value as well. If you’re not interested in this then nothing more is needed to be said. It’s a very straight forward swap and you should have no problem finding someone who is willing to trade your IRS for a straight axle.

If you are having second thoughts and want to know more about why the IRS is a better suspension then a straight axle and how you can make it even better I will be more then happy to explain it to you in detail. You may be glad I did.

 

[TRQJUNKIE]

Thanks again for the input. SlowSVT, I hear what your saying about handling with the SRA. I here though from many people you get almost the same handling with an SRA but it takes a little more effort to get it. I'm done with hop and want to hit the strip more often. I plan on making bigger power down the road and just want something more reliable.

 

[Digital]

I think the whole hurting re sale bit is BS. If your car is making 600-700hp that person is going to see a fully built solid as a upgrade and any fully built solid is worth more $$ then a lightly modded IRS.

 

[injfuel]

sra

I think the whole hurting re sale bit is BS. If your car is making 600-700hp that person is going to see a fully built solid as a upgrade and any fully built solid is worth more $$ then a lightly modded IRS.

very true statement, if i kept my car around 500hp i would never take the irs out but two of my friends broke half-shafts from wheel hop and its very time consuming and expensive to fix

 

[Teej281]

Grrr is getting his sra free of charge, so no need to worry about trading the IRS, and he can keep it if he ever wants to swap back. There has been many cars out there that have done great things with the sra handling wise. You go with a great set of lca's(spherical NOT POLYURETHANE!!!) and a torque arm/watts link or torque arm/panhard bar setup with coilovers, he will be able to handle right there with me and my built IRS and coilover setup. dampers are also a consideration that needs to be made, and I would suggest konis as they can be great for street and any kind of track. We'll talk more Ian. I'll help get you setup right.

Reguardless, the sra can be made to handle right there with an IRS, but will never ride anywhere close.

 

[SlowSVT]

Thanks again for the input. SlowSVT, I hear what your saying about handling with the SRA. I here though from many people you get almost the same handling with an SRA but it takes a little more effort to get it. I'm done with hop and want to hit the strip more often. I plan on making bigger power down the road and just want something more reliable.

What you are hearing about an SRA handling "almost as well as an IRS" is likely coming from people who ditched their IRS and are merely justifying that decision and are only driving in a "straight line". That will get old after a while. Go over to the Cobra R section on this site and ask if they would be willing to swap out their IRS for an SRA and see what their reaction will be?

Here is a Q&A article off the Maximum Motorsports web site that may be of interest:

Test driver Dave Royce answers questions about driving the IRS.

First race win for the newly-IRS-equipped MM American Iron racecar came with the first race entered, and in the process a new AI track record was set at Buttonwillow Raceway. After the race, MM driver Dave Royce answered some questions about the experience: He compared driving the MM racecar with the IRS to driving the same car when it had a Solid Axle, Torque-Arm, and Panhard Bar (SATAPB).

Q: Were there any differences during corner entry between the SATAPB and the IRS?

A: Corner entry is changed in a way I didn't expect. Like with the SATAPB, the car has great initial turn-in. However, once the car is set, it seems more stable from turn-in to mid-corner, or the apex. This allowed for faster corner entry and earlier throttle application.

Q: How does the IRS compare to the SATAPB during mid-turn?

A: Long, high-speed turns are always a challenge in a Mustang, and the entry and exit play a huge role in how well the middle of the turn works. However, sticking to the question; Mid-turn is quite good. With the SATAPB, I would have to wait just a little, through the middle, and then use the incredible launching capability of the Torque Arm to get great straightaway speed. With the IRS, I was able to apply the throttle just after turn-in, and maintain some throttle application throughout the middle of the corner.

Q: How well did the IRS cope with transitions, such as the quick right-left-right changes found in S-curves or slaloms.

A: The key to a great handling chassis is how it transitions, or handles the weight transfer. The IRS maintained composure throughout the esses. I was able to run full throttle through the esses, and would often touch the curbs without having to apply corrective inputs.

Q: Was there any wheel hop during the standing start?

A: The launch was probably the most surprising to me. I had done zero launches with the IRS, so I was ready for one of two things; either a mild to severe wheel hop, or a hazing of the tires. I was sure it wouldn't just free-spin, as it had decent grip out of the low speed corners, so I put that possibility out of my mind. Much to my surprise, the car hooked up with absolutely no wheel hop. I believe the tires were hazing, or slightly spinning, but I was able to keep rolling on the throttle until it was time to pull second gear, and so on.

Q: Compare the SATAPB and the IRS in how the car reacts to hitting berms, and other variations in the track surface, such as large bumps or dips.

A: When hitting "berms" the SATAPB, or more specifically straight axle, as I don't think the Torque-arm and Panhard Bar is a major contributor to this change, would usually set the back of the car over, or upset the balance to the point where I would have to induce correction. The IRS does what you would expect. It leaves the outside tire with full contact, while the inside tire rides over the berm. This was very noticeable in high-speed corners where there is a small steep berm that usually must be avoided. I was able to allow the inside rear tire to be on the berms, and not have to lift off the throttle.

Q: How was the braking with the IRS, compared to the SATAPB? Was there any rear brake hop?

A: Braking was a little better. The biggest advantage was the ability to do more trail-braking, deeper into the corner. No detectable wheel hop under braking was experienced.

Q: What were the best features of the car with the IRS?

A: Terrific transition and mid corner grip. I am able to roll onto the throttle earlier, and have the ability to negotiate berms and curbing without upsetting the car.

Q: People often complain about wheel hop during acceleration with IRS cars. Was this a problem you saw with the MM race car?

A: With the setup from MM I completely forget that IRS has a wheel-hop issue. In fact I can say there is no longer a need to associate wheel-hop with IRS, at least with the set-up I drove from MM.

Q: How did the MM car, in its current IRS form, compare to other road race cars you have driven?

A: The MM Mustang was comparable to the GT3 Porsche in a lot of ways.
Q: Did the MM products on our IRS cure any issues or complaints you
observed when testing any other IRS-equipped cars?

A: Yes. Some IRS cars have undesirable bump-steer. That was not a problem with the MM IRS.

Q: What difference did you notice, between a car with MM IRS products and an unmodified, stock Cobra IRS?

A: As compared to the stock Cobra, with a street set up, it's night and day. The OEM car seemed to float around in the middle of the corner, and exhibited unpredictable traction or wheel spin. The MM suspension, felt positive. Mid-corner predictability seemed vastly improved.

___________________________________________________End of article


The IRS removes 65 lbs of unsprung mass off each rear corner compared to an SRA and is fully adjustable for camber and toe-in. Ford put considerable time and effort to equip the Cobra with an IRS and they would have never done that if it was not an improvement over a solid axle. The added weight of the IRS assembly will also balance the car better. The 125 lbs it adds is the price you pay for a more sophisticated suspension.

Something tells me you will be taking your car to a drag strip "occasionally" but the majority of the time it will be driven on the street. A car correctly set-up for hard launched will make for an awful street car and they only have an advantage just off the line where it will quickly give up that advantage. Having a car built to go in a straight line won't be as much fun to drive as a car that does everything well. Chances are you won't win races just by having an SRA and will be giving up the advantages the IRS provides.

Before you make a decision use the search function under the thread title and type the term "IRS" or "SRA" under the "driveline" and "suspension" sections on this site and read thru some of the post and educate yourself on the merits of both set-ups.

Also go to Maximum Motorsports web site or PM AC427Cobra (Bruce) on this site who has extensive experience with the Mustang IRS. Ask Bruce about his Delrin IRS bushing kit that will cure your wheel hop issue and plant your rear suspension like no SRA can achieve. Here is his web site:

Full Tilt Boogie Racing

I think in your case as you learn more this swap it will start to loose its appeal.

 

[SlowSVT]

I think the whole hurting re sale bit is BS. If your car is making 600-700hp that person is going to see a fully built solid as a upgrade and any fully built solid is worth more $$ then a lightly modded IRS.

Perhaps for some.

But anyone who is looking to buy a Cobra and see's a solid axle out back the first thing that will go thru his mind is: "this car has seen a lot of drag racing" and when considering the punishing shock loads that inflicts on the chassis and driveline it's likely he will quickly loose interest and look elsewhere (I know I would). Not only that but the NE Cobra is the only Mustang ever made with an IRS which makes it special and adds to the appeal of the car.

 

[Teej281]

SlowSVT...please explain to me why in hell GRIGGS would ditch the IRS in their own shop 03 Cobra and go with a Torque Arm/Watts Link setup? I mean they could have decided to make bushing kits to solve the problems of the IRS, but they installed a ta/wl setup. I bet that that car would run right with a built IRS in the twisties.

 

[SlowSVT]

SlowSVT...please explain to me why in hell GRIGGS would ditch the IRS in their own shop 03 Cobra and go with a Torque Arm/Watts Link setup? I mean they could have decided to make bushing kits to solve the problems of the IRS, but they installed a ta/wl setup. I bet that that car would run right with a built IRS in the twisties.

Let me see if I got this one straight.

You are trying to convince him to swap out for an SRA with pan hard rods and watts linkage yet you went thru the trouble of swapping out the SRA in your GT for an IRS? That doesn't make any sense!

Why Griggs ditched an IRS for an SRA I have no idea. No road racer in his right mind would do that. Just because Griggs did it doesn't mean you should. That article I posted provides ample evidence why you shouldn't. It appears you took the opposite stance that Griggs did so maybe you could answer this question better then I can.