A guy on a Nissan forum asked why he should keep his 2 piece drive shaft in his truck instead of changing over to a 1 piece version.
This was the answer I gave him:
The 2 piece drive shaft (DS) is meant to prevent the drive shaft from pulling out under extreme axle movement.
The front of the DS slips into the transmission.
The rear of the DS bolts to the rear axle.
As the suspension travels, a conventional 1 piece DS slips in and out of the "slip sleeve" (my term) at the transmission.
If the "slip sleeve" is short, there is not much room for the axle to move ...or it will fall out.
A 2 piece DS fixes the shaft at a central point, preventing the "slip sleeve" from coming out as the rear axle moves around.
Also, a 2 piece DS will absorb some of the vibrations when a DS is out of alignment (due to dirt or getting bent).
That's all I see, anyway. There could be other reasons.
OK, now that I've satisfied that person, I want to know the actual reason why automotive manufacturers elect to use a 2-piece drive shaft as opposed to the "less expensive to manufacture" 1-piece drive shaft.
Can anyone tell me this?