[why?]

Originally Posted by prandelia

Yeah, that is interesting, and comforting at the same time. It is also worth noting that I have SPL solid subframe bushings, and we "raised" the subframe about 0.5" toward the body (to allow for better axle angles after lowering the car), and this also slightly affects the drive angles. Nothing extreme, but it seems it may be more related simply to the AL construction than anything else, given others also note the same vibration.

The easy way to find out is to slap my OE drive shaft back in, and if it goes away, then we have our answer. Perhaps CF driveshaft would be better.

I bought my AL one locally for only $200 so couldn't resist it, so it's not a huge deal if I move away from it. It definitely felt like more of a "whole car" vibration, and while I've felt engine harmonics that bad, I can see how it might be the AL driveshaft as well.

Anybody with CF driveshafts notice anything similar?

I've seen lots of people on here with AL shafts that complain. Not as many with CF. I have a carbon one from driveshaft shops and I have a tiny increase in whine, but no added vibrations. I've had it in for about 20,000 miles so far. Note at this point my car is mostly stripped.