meansam,
I don't agree with your explanation of the difference between sprung and unsprung weight and torque tube or not.
Not all of the torque tube is unsprung weight, Actually only a portion of it is, and a portion of it is not, as it is nearly fixed. So to simplify things lets say that a certain % of the torque tube is unsprung weight.
The same thought applies to the springs, as part of the springs move with the axle, and part stay almost still, so a fraction of the spring weight is calculated with the unsprung weight. Clear right?
So, the drive shaft will follow the same rules, and part of the weight of the drive shaft can be added to the weight of the axle for unsprung weight, same as the torque tube. Thus, there is no advantage or disadvantage when it comes to sprung and unsprung weight and torque tube or open drive line. If the drive shaft weighed less than the torque tube it replaced then I suppose you could say drive shaft is better, but I think that the weights of each system are very close, so the supposed advantage is negligible.
Grigg
