New Tranny gasket leaking

[2ndwind]

Sunday I decided to replace my trans gear oil with 90W GR-1 because I don't know what the previous owner put in it. I got a cardboard gasket and oil from Vick's. There was no transmission oil leak prior to my doing this. Today I discovered quite a puddle under my car. Jacked it up and saw it was leaking at the back of the gasket. Tightened bolts a little more but didn't want to strip them, continued leak.

I took the pan off and inspected. The gasket was properly aligned with no folds, misses bolt holes, etc. I ran a metal file over the pan bolt holes to test for flatness, most were a bit high but not excessively so. I hammered them flat over the back of a 3/8 socket. Any suggestions before replacing and pouring gear oil back into it? Would a second cardboard gasket be better. Is the gasket material at Autozone any better? Thicker? I'm trying to avoid doing this a third time.

[ventura ace]

I just went through a similar challenge, and ended up using Black RTV silicone to seal. I haven't driven it yet, but it has been filled with oil and sitting for several weeks with no leaks.

Alvon