spewing 727

It's pretty unlikely it came from the vent because the vent is just that, a vent. It vents to the inside of the trans. For it to spew out of the vent the entire case of the trans. would have to be pressurized. It is possible the gasket behind the front pump blew out. It has a passage that leads to the front clutch carrier which is one component that provides reverse. It's possible there is an issue with the B&M kit that caused it. I quit using B&M (and TCI) due to problems such as this. I only use Trans-Go kits now. In the 16 yrs. I've used trans-go never had a problem.

P.S. I've attached a picture of the oil ports so you can pressure test it before tearing the whole thing apart. To do it all you have to do is take the pan off and valve body out. Use 30-40 psi of air pressure and apply pressure to the front and rear clutch apply ports (wear safety glasses cause oil may blow back at you). If oil (or air) blows out of the front pump area it's a good indicator that that pump gasket is blown.