Thread: SPF Axles??
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Old 06-11-2019, 12:27 PM
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eschaider eschaider is offline
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Location: Gilroy, CA
Cobra Make, Engine: SPF 2291, Whipple Blown & Injected 4.6
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Originally Posted by LMH View Post
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!

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.

Help 'em do what they would have done if they knew what they could do.

Last edited by eschaider; 06-11-2019 at 08:55 PM.. Reason: Spelling & Grammar
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