Does front driveshaft turn or (coast)when in 2WD?

gmcman

Well-Known Member
As the title says....just curious if the front driveshaft rotates when in 2WD. I understand it shouldn't have torque applied, but does it remain stationary or rotate with the front diff?

I'm not sure if that side of the diff was open.
 

6716

Well-Known Member
I think it does because I drove in 2wd today, and I heard the front propeller shaft making noise against something. Still haven't driven much since the transmission rebuild, so not sure what I didn't do right there, but I think it was spinning.
 

Mooseman

Moderator
It "shouldn't". With the right axle disconnected, the left is still spinning in the diff, which would be the spider gears inside to spin as the path of least resistance. Maybe at higher speed the driveshaft might spin a bit due to internal drag. Would be interesting to set up a camera and see for sure.

As far as how much MPG improves with it not spinning is debatable. I removed the axles on the Saab's AWD and didn't see any difference.
 

Reprise

Lifetime VIP Supporter
Surprised no one mentioned raising the rear & monitoring directly, since it's selectable 2/4wd. Could probably observe at idle, in gear. Even easier if a helper is available.

On edit - make sure the front wheels are chocked, so there's absotively no chance of a roll. Or raise all 4 off the ground, but that's a bit more work.
 

TollKeeper

Well-Known Member
It does spin, although at a lower speed. The input coming from the drivers side front axle, it splits the spin (relatively speaking) in between the passenger side, and the drive shaft.
 

HARDTRAILZ

Moderator
I think you can even stop the spin by hand with the truck lifted up.
 

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