Loose transmission filler tube

I purchased a BB 727 transmission last week. Previously, someone used pipe tape to snug the filler tube to the transmission. I cleaned this out and removed the tape. Now, I am afraid to add new fluid because this filler tube seems LOOSE. It only has that little "O" ring. Should there be another rubber grommet that is missing? The hole on the trans doesn't seemed rounded out or anything, just seems like this tube is too wobbly and loose.
Any thoughts? Thanks!