[JSchmitz]

Originally Posted by Rich-Tripower

Diff vent is brand new. Issue is not there.

A spline leak is a few drips here and there, this thing is basically gushing, like an open artery. Besides, the splines were sealed every time it has been taken apart.

Ok. Makes sense about the splines. I would remove the vent and blow through it. Like johnta1 said, it could be new and bad. I've seen many gearboxes replaced mistakenly because of a missing or clogged vent. No seal in the world will hold it back if it isn't vented.