Rear Differential Vent Tube

I would think so. It's a VENT tube, not a plug.

When the rear end gets hot, fluids & everything expand, and moisture/condensation collected in the rear diff can boil or the fluid expand. Without the vent tuvbe, you would blow an axle seal or something, with the pressure increase... not good.
The vent allows this pressure, and vapour to escape. When I run mine on a Road Course, the Vent tube will actually puke a little rear end fluid out the rubber hose (just a touch), because the rear-end gets hot, and this is normal.
However, you should NOT be able to blow back into it.... where would the pressure go ? There should be a rubber hose about 4" long (approx) coming off of that vent fitting which should curve down towards the ground.
Make sure the Vent & hose function properly (ie. make sure Vent fitting is debris free) & clear).
Mach1steve
www.muggziperformance.com

I used moroso climbing gear lube on a roard course once it climbed out of the tube like mad! if your doing a road course get a clear catch container for your diff it's worth it.

you did it right !

Mach1steve