what's the rubber tube with a plug in it attached to shroud?

[John Redcorn]

I replaced my radiator a few nights ago with one from radiatorbarn.com ($145 delivered and it seems fine so far) and saw a 3/8 rubber tube with a little plastic plug in the end. clipped to the driver side of the top fan shroud.

with all the huge mess of evap junk right there I couldn't really see where it went, plus it was way cold outside.

 

[95TwinTT]

Maybe the breather tube from the front differential....

 

[bowhunter22]

Just did a rad the other night as well . It is the breather tube for the front diff. Confirmed this by changing the front diff the week before.