I usually use permatex copper for everything. You shouldn't need any for the transmission pan. In fact, it is not recommended, as it can act as a lube helping your gasket slide out of place as you tighten things up. Another reason not to use silicone is that pieces of it will break off and plug something important in your transmission. It has a lot more tiny holes and valves in it than your engine does.Originally Posted by nfpgasmask
If you do put some on, apply a little to the pan first, put the gasket on, then let it dry a bit so it acts as an adhesive instead. Still, it's best not to use any at all. Just clean everything well and the gasket will be fine.