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03-28-2010, 06:36 AM
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CC Member
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Join Date: Mar 2001
Location: E BRUNSWICK N.J. USA,
Posts: 3,841
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Not Ranked
The question is a little vague??
charlandk Kevin, The way I read this question is are you running an open carrier read or looking at a posi one?  If this is it, Posi over open, reasons why are many. Depending on which carrier you get, it's about putting power to the rear tires and movement. Posi in a straight line both tires work, open rearend in a straight line the r/r tire works only. There are 4-5 kinds of posi's. clutches, air, worn gears, mini lockers, mini spools. The question is what kind of HP is the motor going to have, what are the trans ratio's in the trans you are looking to run, what kind and size tires are you going with?? IMO a posi is needed in any cobra with 300hp or more for control of the car.
Kevin if you have the info on your car on another thread, it would be nice to know. You have not really said what you plan to use the car for?? Cruising, Shows, autocross, road racing, stress release, or chick magnet???
The other question is without knowing the HP and more important thing, TORQUE you are leaving more questions that need answers. A stock rebuilt Jag rearend is good for about 450HP and Torque. Some other rearends will take more or less power limits before breaking. If you normal drive the car, no additional improvements need to be made. If you are going for heavy abuse you need to look at better output shaft assemblies that are good for 750-1,000HP. Chromemoly stub shafts in the carrier. Better sidegears in the carrier and even blueprinting the unit itself. OVER BUILT your car.  This way it will take some extra abuse and not break down on the side of the road from a drive train failure. The rearend in my car is all heavy duty parts. Chromemoly shafts, 30 spline locker, heavyduty end supports, gridle for the carrier caps. HP rating is in the 650 range. Been racing this setup for 12 years and no failures. The first year I broke a stub shaft bearing, have had no failures since then. Have gone from 448ft of torque to over 600ft of torque, same rearend and tires. Time will tell about failures of these parts. Rick L.
Last edited by RICK LAKE; 03-28-2010 at 06:38 AM..
Reason: brain farting
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03-28-2010, 08:52 AM
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CC Member
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Join Date: Feb 2010
Location: westfield,
ma
Cobra Make, Engine: BDR # 866 Roush 427 SR/TW
Posts: 101
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Not Ranked
Hi Rick
I posted the the motor choice in the first post, but here it is again......
Roush 427 sr/tw aprox. 515 hp & 525 ft. lbs mated with a T-56 tranny
Rear gear will be either 3.73 or 3.91
As for use, general cruising. Not planning on track racing at this time, but that may change after a year or two. Shows and general cruising. I do have a bit of a lead foot and while to dont plan on "abusing" the car, I will get on it here and there....
Kevin
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03-28-2010, 09:08 AM
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Senior Club Cobra Member
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Join Date: Jan 2001
Location: Santa Barbara, Ca.,
ca
Cobra Make, Engine: R.U.C.C. with a 427FE, toploader
Posts: 1,435
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Not Ranked
My 9" is just fine, but get a L.S.D.!
__________________
Mike Z
Nothing sucks more than that moment during an argument when you realize you’re wrong. 
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03-28-2010, 10:07 AM
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Half-Ass Member
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Join Date: Jun 2005
Cobra Make, Engine: ERA #732, 428FE (447 CID), TKO600, Solid Flat Tappet Cam, Tons of Aluminum
Posts: 22,005
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Not Ranked
There is just no comparison...
Kevin, I won't point you to the ERA site (which has a lot of very nice information on rear suspension geometry) because people tend to think I'm ERA biased to begin with.  Instead, I'll point you to someone else who I view as being a 5-star Cobra suspension genius. Tom Kirkham is on record in this forum as saying that the IRS in the original Cobras was superior to almost all of today's replicas and superior to absolutely everything that has a live axle. You can do a search to confirm this, and if you can't find those threads, I'll do it for you (just ask  ). Suffice to say that in a Cobra, a live axle is better than no axle at all, but it just pales in comparison to an IRS. |
03-28-2010, 12:43 PM
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Senior Club Cobra Member
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Join Date: Feb 2007
Cobra Make, Engine: KMP 539, a Ton of Aluminum
Posts: 9,591
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Not Ranked
Live axle is better for drag racing. IRS is better for road course. And the Cobra is dangerous, no matter what rear end you have installed.
Everyone is right. Can I get a Hallelujah?  |
03-28-2010, 12:46 PM
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Half-Ass Member
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Join Date: Jun 2005
Cobra Make, Engine: ERA #732, 428FE (447 CID), TKO600, Solid Flat Tappet Cam, Tons of Aluminum
Posts: 22,005
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Not Ranked
Quote:
Originally Posted by RodKnock
Everyone is right. Can I get a Hallelujah? |
No, but you can get this, which will save Undy & Lykins some time.... 
Last edited by patrickt; 10-24-2016 at 01:20 PM..
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03-28-2010, 02:51 PM
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Senior Club Cobra Member
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Join Date: Feb 2007
Cobra Make, Engine: KMP 539, a Ton of Aluminum
Posts: 9,591
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Not Ranked
I don't Tom meant in ALL applications.
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03-28-2010, 03:15 PM
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Half-Ass Member
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Join Date: Jun 2005
Cobra Make, Engine: ERA #732, 428FE (447 CID), TKO600, Solid Flat Tappet Cam, Tons of Aluminum
Posts: 22,005
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Not Ranked
Quote:
Originally Posted by RodKnock
I don't Tom meant in ALL applications.
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... just 99.9% of them. |
03-28-2010, 03:17 PM
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CC Member
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Join Date: May 2001
Posts: 1,330
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Last edited by TButtrick; 03-28-2010 at 03:20 PM..
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03-28-2010, 03:28 PM
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Half-Ass Member
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Join Date: Jun 2005
Cobra Make, Engine: ERA #732, 428FE (447 CID), TKO600, Solid Flat Tappet Cam, Tons of Aluminum
Posts: 22,005
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Not Ranked
Quote:
Originally Posted by TButtrick
Patrick,
Are you making up technical terms again?  |
Well I'll be damned, I googled the exact phrase "solid axle torque steer" and my use of it was the only result. But it's a real thing, nonetheless. I bet you googled it too before you posted that. |
03-28-2010, 03:39 PM
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CC Member
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Join Date: May 2001
Posts: 1,330
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No.. it's not a real thing. There is no such thing as "solid axle torque steer". Never was, and never will be. Torque steer references are reserved for front wheel drive cars. The only exception might be monster trucks that have rear wheel steering.
Tom's statement is 100% correct. IRS is a more technically advanced suspension. ( he also said that spinners that tighten toward the front or no different from spinners that tighten toward the rear.  ) I'm just not swallowing the hysteria that solid axles are dangerous and irresponsible in these cars. Maybe Jay will chime in? |
03-28-2010, 03:43 PM
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Half-Ass Member
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Join Date: Jun 2005
Cobra Make, Engine: ERA #732, 428FE (447 CID), TKO600, Solid Flat Tappet Cam, Tons of Aluminum
Posts: 22,005
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Not Ranked
Quote:
Originally Posted by TButtrick
No.. it's not a real thing. There is no such thing as "solid axle torque steer".
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I know you hate the ERA site, but they have some beautiful graphics on there that you, and others, might actually like.
"A solid rear axle can be a severe handicap in a short wheelbase, high performance car like the Cobra. Torque steer under high acceleration can create a rather unstable situation. There are some live axles that compensate for the driving torque, but everything is a compromise: Normal bump characteristics will suffer then." http://www.erareplicas.com/427/rsusp.htm |
03-28-2010, 03:56 PM
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Senior Club Cobra Member
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Join Date: Feb 2007
Cobra Make, Engine: KMP 539, a Ton of Aluminum
Posts: 9,591
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Not Ranked
Quote:
Originally Posted by patrickt
... just 99.9% of them. |
Oye vey. Patrick once again making up percentages. |
03-28-2010, 04:00 PM
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CC Member
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Join Date: May 2001
Posts: 1,330
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Actually, I'm a pretty huge fan of ERA as you know but because it states that on their web site, it doesn't make it so. The statement " Torque steer under high acceleration can create a rather unstable situation"... simply is not true nor based on fact when referenced to live axle, rear wheel drive car, with functioning components. You did see the pics I posted, yes? IRS would be just as prone to some distant reference to torque steer if a lower or upper control arm failed.
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03-28-2010, 04:11 PM
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Half-Ass Member
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Join Date: Jun 2005
Cobra Make, Engine: ERA #732, 428FE (447 CID), TKO600, Solid Flat Tappet Cam, Tons of Aluminum
Posts: 22,005
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Not Ranked
Quote:
Originally Posted by RodKnock
Oye vey. Patrick once again making up percentages.
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What?!? "Never, never on a Sunday, a Sunday..." Much less today.
Quote:
Originally Posted by TButtrick
You did see the pics I posted, yes? IRS would be just as prone to some distant reference to torque steer if a lower or upper control arm failed.
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Yes I did. And I'll also admit that you're a very smart guy. I'd also like to hear from some of the other truly gifted Cobra builders on what they think of the issue. |
03-28-2010, 04:56 PM
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CC Member
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Join Date: May 2001
Posts: 1,330
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Well, it really doesn't take anything more than average intelligence to understand the dynamics of suspension but I guess this might be beyond your understanding.
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03-28-2010, 04:58 PM
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Half-Ass Member
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Join Date: Jun 2005
Cobra Make, Engine: ERA #732, 428FE (447 CID), TKO600, Solid Flat Tappet Cam, Tons of Aluminum
Posts: 22,005
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Not Ranked
Quote:
Originally Posted by TButtrick
Well, it really doesn't take anything more than average intelligence to understand the dynamics of suspension but I guess this might be beyond your understanding.
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Dang, and you didn't even include a winkie with that gratuitous kick in the balls.  |
03-28-2010, 05:01 PM
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Senior Club Cobra Member
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Join Date: Jan 2001
Location: Santa Barbara, Ca.,
ca
Cobra Make, Engine: R.U.C.C. with a 427FE, toploader
Posts: 1,435
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Not Ranked
I think Patrick gets a bright shiny penny ever time he types ERA here!
__________________
Mike Z
Nothing sucks more than that moment during an argument when you realize you’re wrong.
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03-28-2010, 05:04 PM
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Half-Ass Member
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Join Date: Jun 2005
Cobra Make, Engine: ERA #732, 428FE (447 CID), TKO600, Solid Flat Tappet Cam, Tons of Aluminum
Posts: 22,005
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Not Ranked
Quote:
Originally Posted by Ibr8k4vetts
I think Patrick gets a bright shiny penny ever time he types ERA here!
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But if I were building a single purpose track car tomorrow, it would be an FFR. |
03-28-2010, 05:13 PM
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Senior Club Cobra Member
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Join Date: Jul 2002
Cobra Make, Engine:
Posts: 15,712
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Not Ranked
,,,an FFR with IRS for me please. Been there done that with a live axle, IRS is clearly superior in my experience. Most notably in the "ride" department, not to mention better handling as well. Not that a live axle can't be made to work, and work well, but it's not that common compared to IRS.
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