[cre]

Actually, the two piece is more to do with longevity and preventing the DS from grenading on you (and yes, it helps with vibrations but don't put it past Toyota to know how to build a balanced drive shaft... They would have if not for other factors , I'm sure, they're MUCH cheaper). You can find a LOT of information on this already online including a lot of wonderful pictures of exploded one-piece DS'd sticking out rear seats or gas tanks or taking out cars behind the vehicle it was installed in. It's the whole reason DS loops/cages are required at tracks. It's all about elasticity, centrifugal force and the outward fatigue it causes. Aluminum is the most susceptible (also the worst for vibration), steel is less susceptible and CF the least (although I believe CF may have more vibration tendency than steel).

I'll see if I can find a calculator for critical rotation speeds (this is just the speed at which the most stress is seen, it doesn't mean that if you drive at that speed one you're dead... I think on the 4.30:1 it was something low like 80MPH with a one-piece aluminum DS and stock size tires).

Bah, I don't have time today to dig for all the fun pictures Google image search used to show, they've changed the sorting priorities of something. Anyway, from what I've seen with fatigue the metal shafts will spiderweb and tear in multiple places. From too much power it usually looks more like a torn paper towel roll or crumpled. Carbon fiber looks like an expensive broom when it goes (not a lot of damage potential other than the spline and forward U-joint).

The Stock two piece has a critical rotation speed about three times that of a one piece. The two piece also serves to dampen shock through the drivetrain. You can get a lighter two piece made for little money and retrofit a more common carrier bearing OR have a one piece with a thicker center sleeve welded in essentially shortening the drive shaft into two and thus raising the ceiling a bit.

Vibration will kill seals, bearings and U-joints but the DS isn't going to just pop like a cartoon gun with a finger in it.

Of a final note a lot of drive shaft shops will tell you you need to check the DS every few thousand miles for signs of spider webbing or cracking (especially one this long)... do it; It's cheap insurance and really beats having the ass of the car try to pole vault on the highway. I've only known a couple people who've had trouble with their on-piece DSs on MKIIIs, those were aluminum. I've always run steal (on various cars) and never had a problem.