I recently put an aluminum driveshaft back into my car.
The aluminum one I had before I put in the gearvendors behind the original A4 had what looked like a harmonic balancer built into the snout so we couldn't weld the Turbo 400 snout on and use it.
We used and shortened the original steel one.
When I took the gearvendors and A4 out of my car for the M6 I got another steel driveshaft but this time it had the same type of harmonic balancer type thing built into it while the aluminum one I just got does not have the balancer.

I was wondering if anyone knew why they had 2 different types of driveshafts and which one is better.
I have the aluminum one in now but still have my steel one with the balancer.
I haven't noticed any real difference driving on the highway.

 

I think the steel one may have been a little stronger. They used them even on the LS1's if you got the 2.73 gears- my car came so equipped. The Aluminum DS was used to save weight, first in the 1LE, then in some of the other Camaros. Besides weight, it was lighter in rotational inertia, too, making the car a little quicker to accelerate, though not any faster on the top. There was a factory service bulletin about driveline vibration that allowed the dealers to sometimes replace the steel DS with an aluminum one if the customers were complaining about vibration.

 

Ok
Well I've got both.
The steel one is smooth at 100mph.
I'll save the steel one in case I ever go to 14lbs of boost
and twist up the aluminum one.

 

See if you can find a copy of the Service Bulletin 67-41-01 from 1996- explains the problem and the trade-offs pretty clearly.