Absolutely nothing beats the Mopar RTV for sealing transmission pans for ATF, that is what it was designed for. They used to have a specific ATF RTV and an Engine RTV that was grey. When the Threebond came out, Mopar just relabeled the ATF RTV as simply RTV, and the grey Engine RTV went away. It has always been my go to for pretty much everything until Mopar starting using ThreeBond RTV on the 3.6 engine. Threebond is pretty amazing for aluminum to aluminum sealing needing RTV without a gasket. If you use Threebond, be prepared to fight the two parts to get them apart, about twice the effort of the Mopar RTV. I still use both on engines, transmissions and differentials, reserving the Mopar RTV for dissimilar metal sealing, anything with ATF, or anything that gets regular maintenance. I use Threebond on aluminum to aluminum sealing that I don't want to leak...ever!