Crack through mating surface of transmission pan
Crack through mating surfacing for bellhousing
Backside of bolt hole
back story is truck is a 2001 silverado 5.3 2wd with cam and stall. I did a rear main seal replacement and removed the transmission but only lowered it on a trans jack and rolled it out of the way with the converter still in it. After changing the rear main I reinstalled the trans, then removed the pan and put a new filter in (pan is a B&M cast aluminum +3 quart. It’s beefy) I applied a bead of gasket maker around the pan, let it set for an hour and reinstalled per directions on the RTV bottle.

No more engine oil leak from the bellhousing but the underside of the truck was (and is) COVERED in transmission fluid. Seemed to be coming from the bellhousing so I assumed it was a pump bearing failure from me misaligning the converter to the flex plate and causing a bind. I noticed the fluid was coming from between the bellhousing and trans case but also inside the bellhousing and leaking off the converter (Makes sense after seeing pics). When I removed the trans to do the pump. I took the pan off and that’s when I found this large crack through one of the pan mounting bolt holes at the front of the transmission.

I have seen this when there is some debris between the pan and trans housing when tightening the pan bolts. Usually with aluminum pans but I guess it can happen with steel as well. It can also happen when torque specs and patterns are not followed correctly. Again, steel pans and thick gaskets are pretty forgiving, so I usually see it in aluminum to aluminum matings.