SPF Axles??

[JBCOBRA]

Cool!
Thank you Ed!
Calling them right now

[eschaider]

Originally Posted by LMH

Ok, now I understand more! I do disagree on one point eschaider is making and that’s the Mustang Cobra differential. 2003 and 2004 Cobra IRS differential is aluminum, super strong and not the same as other production IRS units. It’s what I had on my Hurricane. 31 spline CV joints while 28 is standard. Very stout if you abandon the stock rear cover for an aftermarket one. Otherwise, switching it is an excellent idea!
Larry

You are right about the 03/04 IRS being not the same as all the other passenger car units, Larry. The difference however, is in the axle spline count and positraction carrier. Both need to support the 31 spline axles that the Cobra's came with. Virtually (but not all) all the other Ford proletariat vehicles came with 28 spline hardware.

When you get into what is essentially a light truck the spline counts jump back to 31 up from the normal 28. The actual castings are all the same except for the Explorers. The Explorers got the HD double anchors at the snout and slight differences in the main casting. From a housing perspective it was the strongest aluminum casting for the 8.8 gear set Ford offered. Depending on what you filled them with for internals and side gears, they were better or worse. The best solutions have always been the 31 spline hardware.

Instead of a positraction or a locker (which is tough on the street) I elected to go with a Wavetrac all gear torque biasing differential, click here =>Wavetrac. Be sure to enable your flash player to see how it works. Their biasing mechanics are elegant simplicity.

Several things impressed me about the Wavetrac differential;

⦿ It is entirely made from forged and or billet components

⦿ The 12 load carrying gears are machined from 9310 steel. No other manufacturer offers 12 pinions and I believe Wavetrac was alone in making them from 9310 — but I am not certain of the 9310 exclusivity.

⦿ No matter how you use it, it is covered by a lifetime warranty! That includes racing, rock climbing and daily driver activity.

I found them impressive in the extreme.


Ed

[LMH]

The 31 spline CV joints used to be hard to come by but I’m told now there are aftermarket companies making them. I had to search a while before I found mine. Mounting is the same as T-Bird. I wish 4HU stuff was as cheap, let me tell you!
Larry

[JBCOBRA]

Hi Ed!
I sent G-Force all the info you provided and with some luck they can figure out if the ones you got from them will fit my car too.
Thrilled with G-Force already, because they are nice and actually answer the phone, email back right away. Wow. What a Treat

[JBCOBRA]

Oh well,

I'm sorry John but without more information we aren't going to be able to do much for you. I just searched the old system for your friend's order and found nothing under his name. Do you know what the spline count is on the rear end? You would have to be using a rear end and outers that we already make components for. Such as an 8.8 31 spline rear end and S550 or Cobra outers.

[eschaider]

Originally Posted by JBCOBRA

Hi Ed!
I sent G-Force all the info you provided and with some luck they can figure out if the ones you got from them will fit my car too.
Thrilled with G-Force already, because they are nice and actually answer the phone, email back right away. Wow. What a Treat

My axles are not for the Australian Dana they are for the Ford 8.8, John. I strongly suspect the Aussie Dana takes different axles possibly even 28 spline. I would not spend money on that rear end. Rear end quality, strength and suitability not withstanding the Ford 8.8 is just a better choice.

The only reason that rear end ever found its way into our cars was the kerfuffle over the Cobra name, logo and shape of the car that was raging between the replica car manufacturers on one side and Ford / Shelby on the other.

SPF either did not want to find themselves w/o a rear end supplier or had been already informed that their orders were no longer going to be accepted. Either way they went shopping and the Aussie Dana was the quick fix — its not where you want to be long term.

The G-Force axles use the 108mm Porsche 930 CV joints with a custom length axle to fit the particular application. G-Force takes the 28 spline OEM inner race and replaces it with a hardened 31 spline equivalent.

Because the 930 joints are so big, 108mm (that's bigger than a 105 Howitzer), you need the special stub shafts to attach to them. The entire assembly needs to be fit to your vehicle. Where your car rides height-wise and where you mount your IRS center section height-wise will impact your axle shaft length dimensions.

If you elect to go the Ford 8.8 inch route with aftermarket axles, it is not an off the shelf bolt in purchase. Because you have the Aussie BTR unit installed right now, the conversion becomes a custom fit solution specific to your car and needs to be treated as such. You will need professional chassis builder help to complete the job unless you have welding and fabricating skills.


Ed

[JBCOBRA]

Dang

[LMH]

Why not just switch it to the 8.8” Mustang Cobra differential and use the Mustang 31 spline setup? It’s all Ford and brings it inline with other SPFs using the 8.8” differentials only stronger. I would think it a lot less expensive yet still way stronger than the standard 8.8”.
There are a couple aluminum diff cases on eBay right now too.
Larry

[eschaider]

+1^


Ed

[saki302]

BTW- if you're planning to swap in a Ford 8.8, it would be worthwhile to read and do the SCOF tech article on drilling and tapping it for a drain plug for future use.

I drilled and tapped mine- it's much harder and messier from under the car!

[LMH]

If you do decide to switch it to a Cobra differential, a couple things I’d do are use a heavy duty rear cover like a FMS or similar with gusseted mount. I’d use solid aluminum mounts in the front plus I would upgrade the center shafts on the axles. DSS can recommend ones.
I’d also change the hub bearings while it’s apart. There won’t be an better time then when it’s apart.
Just my opinion of course!
Larry

[Mark IV]

Originally Posted by LMH

Why not just switch it to the 8.8” Mustang Cobra differential and use the Mustang 31 spline setup? It’s all Ford and brings it inline with other SPFs using the 8.8” differentials only stronger. I would think it a lot less expensive yet still way stronger than the standard 8.8”.
There are a couple aluminum diff cases on eBay right now too.
Larry

The mounts on the frame are different for the Dana vs. the Ford 8.8" so it is not a "bolt-in" operation. It can be done, but takes work.

The BTR-Dana was used in several Hi-Po cars (GTO, Camaro, etc.) and will take a lot of use up to stupid levels of torque so well positioned for use in the SPF. The switch back to the Ford diff was due to discontinuation of the BTR. SPF then went to the ZF units as now used in the Camaro however supply issues have reduced the availability so it is used in the 289 cars as the standard diff (the Salisbury/Jag type or alloy Kirkham/Shelby is optional) and the 8.8" is now back in the MK III (427) cars.

[Randall Thomas]

Rick Mark IV is correct. And while any of the factory differential offerings can be made to fit in any of the Superformance cars, it does not come without significant modification and fabrication. And frankly the performance and reliability history of all their differentials doesn't make one stand out better than the other, and not enough to warrant a swap.

Superformance makes periodic changes to not only upgrade their cars to the latest technology, but also to keep their major components "relevant" so decades later replacement parts can still be readily available for their owners through the aftermarket. Their history of differential selections also follow this same business model.

Some of the first Superformance Mk-III's in the early double digit cars back in 1993-94 came with straight axle 9" rears and later the Jag IRS. Then again, some also came with 351 Clevelands too. They were just getting started and they had no idea of how big they would become.

Example of a early Superformance car #11...
Superformance Owners Forum's SUPERFORMANCE NEWS

Once making "production" cars they went to the cast iron 8.8 IRS from the 1989+ T-birds with 3.73 gears, however the T-bird differentials were not easy to get and to stay relevant, Superformance used the same 28 spline differential found in the T-Bird's cousin, the Lincoln Mark 8. However, those were aluminum cased differentials and these came in the mid 200-300 series Mk-III's starting in 1998. In addition around car 300 the differential was raised to provide additional CV clearance and in 2000 around car 900 the upper mount brackets were reinforced to handle the increased power plants the owners were now using, some up into the 1,000 hp mark. And more.

Ford 8.8 Iron and Alum diffs...
http://superformance.org/differentials/Ford_8-8diff.jpg

Since the 8.8's in the Mark 8 were long out of production since 1998, to stay relevant once again at car 2069 Superformance decided to use the Australian sourced Dana 7.75" B.T.R. found in the 04-06 American GTO as well as the Aussie Holden cars. The gear ratio was 3.46 and this would be December 15, 2004. As a side note the Superformance/Shelby lawsuits were settled on February 5, 2005 where Superformance cars were licensed by Carroll Shelby to be built under his licensing and Superformance was now building the CSX cars for Shelby.

Dana BTR diff...
http://superformance.org/differentia..._7-75diffR.jpg

The Pontiac GTO did not last long in production, for about 2 years and soon after Pontiac itself was defunct by October 31, 2010. So to stay relevant once again Superformance looked for the most recent and equally robust offering which was the ZF rear differential found in the 2010 Camaros. This had a 3.45 ratio and was first installed into cars in the mid to late 2900 series around the beginning of 2010. These were physically large differentials to fit under the car and created a little more driveshaft misalignment which required some chassis modifications at car 2996 to improve those angles.

The photo below is the prototype ZF differential I personally took at the Factory in South Africa in February of 2010. Once viewing the photo, if you click "next" you will see a series of photos of the diff as well as mounted in the car with the axles it uses...
1567mon_hitech_zf_differential1

And once again to not only stay relevant but also take advantage of the latest technology, in car 3315 Superformance began using the new Ford "Super 8.8" cast iron differential found in the 2015-16 Mustangs with a 3.55 gear ratio. This new 8.8 is nothing like the previous older 8.8 unit and will not fit in the older cars with the Mk-8 8.8 differential without significant modifications.

Ford "super 8.8" diff...
http://superformance.org/differentia...per8-8diff.jpg

[JBCOBRA]

Terrific info Randall,
Any idea what axles are in 2218?

[eschaider]

Very nice walk down memory lane, Randall, including lanes I had never visited before. The pictures and look at the inside of Hi-Tech and how they create these cars was absolutely spectacular!

The North American parts availability for the Australian BTR units, component pricing, import expense along with their smaller diameter 7.75" ring gear were troubling for me from a inherent strength, potential need for service and cost of service point of view. The Aluminum 8.8" Ford IRS center was an easy fix for me. A significant contributor to my decision process was the substantial aftermarket support, stateside, for the 8.8 inch Ford unit.

Different resources, different needs and different component availability can move other owners in directions other than the one I had chosen. Probably the most important consideration for anyone considering this sort of modification is, no matter the number of alternatives, the choice of a final solution (if there is such a thing) should address the owner's specific needs and budget. Although not impossible, it is still pretty hard to improve on that type of an ending.


Ed

[tortuga]

Since the inner cv is simply a tri y yoke that rides in a matching three slot cup, I would bet that the shafts with the exception of the inner cv cup (and maybe the snap on yoke) are the same? Anybody with the Dana pop their innocence cv off? On the ford the only thing holding the cv from just falling off (with the axle removed) is just the boot...snap on a new yoke and cup that plugs into the Dana...

Just s guess
Steve H
1764
Ford 8.8

[JBCOBRA]

Hi Fellas,
I finally got the old axles out of my car and they are on the way to Dennis.
Thank you guys for all trying to help me. I though for sure I could buy a set ready to rock!
That would have been the best scenario. SPF didn't even know what was in my car.
I was surprised to find VW inner CV's! Have any of you guys found this on your cars? There has to be something better? ....I hope?

[Mark IV]

Originally Posted by JBCOBRA

Hi Fellas,
I finally got the old axles out of my car and they are on the way to Dennis.
Thank you guys for all trying to help me. I though for sure I could buy a set ready to rock!
That would have been the best scenario. SPF didn't even know what was in my car.
I was surprised to find VW inner CV's! Have any of you guys found this on your cars? There has to be something better? ....I hope?

A lot of Porsche stuff has the V-Dub logo on it so don't judge!

[JBCOBRA]

Hi Rick!
You are right��
I'm a big Vdub fan.

[JBCOBRA]

How about some 930 Turbo CV's?