e-locker mystery wire - need help with ID

I need help identifying a specific tube from an e-locker rear end that I bought at a wrecking yard.
I bought this complete rear end from a wrecking yard and there is one tube/cable (or maybe some sort of sensor) that I cant identify. This rear end was out of a 2003 TRD, V6, auto trans, 2WD, extra cab... if this even matters.
The "tube/cable" in question goes from the differential to the driver's side frame rail and "plugs into" the frame rail itself. When removing this cable form the frame rail I snapped (broke it) it off the frame rail and could not see any type of actual wire inside the cable itself or inside the frame rail leading me to believe that it might be some sort of sensor mechanism that may be somehow associated with the speed sensor system?
What is this mystery tube/cable? I checked my factory service manual and couldn't find any info.
Below are a few pics of the item in question.

rear end assembly at wrecking yard - red arrows and dots show the cable in question


close up pic end of cable after snapped off of frame rail


close up pic of cable at differential


close up pic of end of cable showing it snapped off

 

Looks like the vent hose for the actuator?

 

As mention, ventilation. The other end is pushed into the frame

 

Got it - thanks guys.