Jim
The opening you are using..... is for the return cooled
oil coming from the cooler.... on that rear end cover.
That is a bad place to try to vent from.... if you look closely it is directly in line with the spinning differential where all of the splash is coming from.... If you look at the photo I just posted, it shows the inside of the cover and is just off of the Ring Gear and to low for a vent hole. Also remember as you go around turns and are pulling X-amount of G's... the
oil is trying to get our the sides as well.
So you need to plug that hole. Then go to the top hole on the cover and do the work we did on the inside of our diff to prevent the
oil from pushing out of the rear end.... the oil will sling into the vent hole and then keep pushing oil up to the catch can.... and eventually deplete all of the oil in the Rear End by continued forcing of the oil into the vent hole.
That is why we have a cover over the hole with a fence below it so that the oil coming off of the Differential doesn't get to the vent hole. the large plate keeps the oil from the Ring Gear from getting to the vent hole.
Also only use AN fitting with Stainless braided lines.... you can't get a worm clamp to remain tight on a hose barb made for a rubber hose. especially situations where there is a lot of oil.
