Just found this, http://www.dana.com/Automotive_Syste...propshaft.aspx. So seems like it would be the critical speed (for the long shafts) and the u joints that are probably the weak spots.

Just as a reference, 2200N-m = 1622 ft-lbs, 2500 = 1843

 

Where's the data for critical speeds?

 

you have to calculate it based on lengths. http://www.wallaceracing.com/driveshaftspeed.htm

Keep in mind that is theoretical based on a perfect balance, which many of us have realized isn't what we get from the factory (wouldn't need perfect either with a 100MPH speed limiter).

I used 10.4Mpsi for modulus and 0.10 for density.

 

OK - Thanks!

 

Nice find. Bingo on the balance thing (the limiter comment), makes huge sense that as soon as we lose the limiter and put that poorly balanced shaft on a dyno they die.