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Does a lighter driveshaft balance better and give off less harmonics at cruising. Like it could be quieter.
Since alum usually requires a larger(next) diameter, it likely would be stiffer and therefore less harmonics, etc or they would be a higher freq.  One of my cars has a MW bonded alum/1350, which I like, I asked them years ago about lightweight foam filling an alum bonded driveshaft, they just gave a funny look.
Reality check, that half the population is smarter then 50% of the people and it's a constantly contested fact.
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