Sealant doesn't go on transmission pans. Ever, ever, ever. Period. Make absolutely 100% SURE the pan rail is straight and the bolt holes are not distorted. Don't say "It's a new pan" just frikkin DO IT. How hard is that? Seriously? Next get the best gasket money can buy. That would be this. Rubber with a steel core. Put it on CLEAN CLEAN CLEAN and DRY.
Moroso 93110 Moroso Transmission Pan Gaskets | Summit Racing
Lastly torque to spec and DON'T over torque. Finally, come back after a few heat cycles and re-torque WHEN COLD. If it's the pan gasket that's leaking, that should solve it. But beware, like others have said, transmission leaks can be tricky. Sometimes a pan gasket leak ends up being a dipstick tube leak, of shaft seals, or something else, so inspect it very closely.
