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That our 'Birds are electronically limited to 112mph, when a similarly equipped 'Stang is able to top out at around 135?
 

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It has to do with the limitations of the drive shaft. The speed limiter on our cars is set at 105 to 112 MPH because our stock drive shafts just aren't as good as the Mustangs.

Under the Transmission Tech Articles, Ford OD Transmissions 101 - Jerry's mod, Click on Chapter 17 - Driveline Critical Speed and read 'till your heart's content.
 

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Not that they aren't as good, it's just that they are significantly longer. A shaft has a critical rotating speed, which is determined by several factors. Diameter, length, mass, and rotating speed are all players in the equation, but a longer shaft cannot spin as fast as a shorter one before resonance sets in and its own natural frequency tears it apart. Since changing the length of our driveshaft isn't really an option, people get around this buy installing an aluminum driveshaft to decrease the mass, which helps them turn a higher speed safely.

Pete
 

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Also more importantly than the driveshaft is the fact that GT mustangs came with speed rated tires, and our cars did not. Maintaining those speeds with a stock driveshaft will result in vibrations and wiping out a trans rear seal, but doing it without speed rated tires could cause a blowout, which at 120+ is extremely dangerous.
 

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psh... just throw some ZR tires on some 17's like I did lol
 
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