90404-51319 Union

Can anyone tell the correct size hose to use for the axle vent mod with the above barb/union?

 

That union is made to use 3/8" ID hose but some people have reported 5/16" also works well and is a bit tighter fit. I used 3/8" and it worked fine in my opinion. Don't overthink it, everything you need is in this thread. Good luck and welcome to Tacoma World.

https://www.tacomaworld.com/threads/my-differential-breather-mod-photos.111954/

 

You don`t have the fitting yet to measure?

I am sure 8MM or 10MM will work !

 

Thanks for the information folks