1997 runner
Has anyone ever heard of a diff breather leaking? I filled my diff and put the fill cap back on drove about 5 miles on the highway and stopped. Checked it out and saw gear oil all over! The back sides of both drums are dry and the Pinion seal is dry. Oil Slick everywhere else. I have never seen that before and the only place where it looks to be comming from is the breather. Im stumped Maybe the breather was plugged and built enough pressure to blow out the breather instead of the seals? it still leaks a little after i cleaned it off!

 

I had one on a Dana 44 axle that was clogged and would puke out oil on the highway. Probably due to excessive pressure buildup which then forces the lubricant out. The vent was nothing more than a cap with a spring that kept tension on a rubber disc over a nipple. The 4Runner probably has a similar design. Disassemble it and see what you find.