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Nice. Wow, he has a lot of driveshaft boom in the straightaway. Time for a custom unit with higher modulus I'd say. That boom will take-out your bushings and bearings in fairly short order. Nice to see the old iron showing the 'kids' a thing or two.
:tup:
David
 

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David PSIG, what do you mean by "driveshaft boom"? What does it sound like? Are you referring to some of the noise at about 5:13, what seems to be on a straightaway? What causes driveshaft boom?
 

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David PSIG, what do you mean by "driveshaft boom"? What does it sound like? Are you referring to some of the noise at about 5:13, what seems to be on a straightaway? What causes driveshaft boom?
Exactly. Notice how it cuts-in rather suddenly as it reaches it's harmonic frequency, and then cuts back-out just as suddenly at RPMs drop through the frequency. Driveshaft boom is where the shaft actually begins to get waves in it due to both hitting a critical frequency, and the stiffness (or lack of it) in the driveshaft. Look at it like it was made from stiff rubber. The material has a certain modulus (stiffness) and the diameter and length affect the frequency. You can change one or all three to change or eliminate the boom.

Note for comparison - that a worn transmission output shaft bushing, bad mount, cocked U-joint, etc. give a similar effect, but also has far more vibration with it. If you hear boom cut-in at 'normal' highway speeds, and it blurs vision out your rear-view, then it's one of those. The whole shaft runs and bends (whips) off-center. With boom the driveshaft gets a twisted S-curve or wave in it, and though there is some vibration, you don't feel like it will take the car apart. Similar but different.

David
 

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It was kind of cool seeing the big old bad Ford putting a hurting on some of those more modern "race" cars. Especially the yellow Porshe. I bet he was like, "WTF!?"
 
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