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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?

1 Piece versus 2 Piece Drive Shaft

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2 Answers

up vote 6 down vote accepted

I think it's more related to the angle of the driveshaft from the transmission to the differential. This way you could have more suspension travel without putting too much constraints on parts.

In fact, to answer your question, it may be related to the geometry of the truck/driveshaft that manufacturer will select one type over another one. If the truck is long, you don't want the drive shaft hanging under the truck which can be hit and break.

This is where I took my reference.

DriveShaft angle

Image source

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That's kind of what I'm thinking, too, Gabriel. I found several questions about it on various forums. All I found get distracted into why the person is asking the question, then they spend their energy trying to solve the problem instead of answering the question. –  jp2code Aug 6 '13 at 14:05
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It's all about the working angles. They are designed to apply a small amount of stress which will cancel out minor driveline vibrations. If the angles are incorrect, there can be excessive vibrations and loss of power to the wheels. The two piece driveshaft keeps those working angles to less than 4 degrees, more than that will cause premature u-joint failure –  Larry Aug 6 '13 at 14:55
    
Great answer! The wrong angles anywhere in your vehicle will wreck havoc on any bearings and sealing surfaces. –  FossilizedCarlos Aug 6 '13 at 23:40
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When wheel base distance is between 3.4m to 4.8m then two piece drive shaft as far as L/D ratio concerns

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Would you care to elaborate? Why those lengths in particular? You can have much longer single-piece shafts than that... –  Nick C Sep 20 '13 at 9:46
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