I have a 88 4 runner with 5 speed transmission, I drained fluid, which it had about a half of a quart in it. I put new in it, the amount the book called for 3.7 qts. Had checked transfer case it was over full, so drained it down . drove it about 200 miles and I have fluid coming out of vent on transfer case. checked transfer case over filled again, checked transmission and its low. how is fluid getting in transfer case?

 

It is possible the vent on the transmission is blocked with dirt or has just failed .

The fluid under pressure is being drawn into the transfer case once there it can`t come back.

About the only thing I can think of.

Just how are you figuring the transmission is low on fluid ?? As the normal method is to check at the fill plug .

Add till it starts to come out.

I am surprised with the fluid level that low it does not sound like rocks in a blender.