Toyota do not come with a vent hose. At least not in the lower 48. Even the tacoma and other more popular "offroad" models still come with a vent cap. Here is a picture of our rear diff and the cap.
The vent cap is a simple one-way valve that lets air out but not in (a little in). The idea is that this prevents water from entering but allows for hot expanding gases within the diff to escape. This is problematic for a couple of reasons.
-gunked up after a few years and prevents any venting. The result is typically a leaking diff seal; axle or pinon.
-They allow hot gases to escape, but not cool air back in. When the diff cools often a vacuum will develop within the diff. This can lead to seal leaks
-The vent gets gunked up and no longer stops water from entering.
A popular mod is to remove the vent cap, add a barbed nipple and run a hose up to a higher location. You would need to remove the stock vent and replace. You can not simple add a hose to the top of the vent cap. You can pry the top of the stock vent cap off, remove the spring and seal disk and attempt to hose clamp a hose to the remaining nub, but it is very small surface and hose pops off easily.
Perviously I offered to sell a barbed nipple fitting, however I have since done more research. It appears that the vent on the RAV for both the rear diff and the transfer case are fixed. Possibly pressed in place. The base of the vent is round and smooth. See the picture above. I confirmed this last night on my RAV. From picture searches the from Transfer case is the same.
Thus the threaded vent nipple that works on the solid rear axle of the tacoma/tundra/4Runner/FJs... do not work on our RAV. :frown
Not sure I would be willing to pop off the cap of the stock vent and try to fix a hose to it.