64-78 C4/C5 Automatic Trans Premium Pan Gasket

FARPAK Coated Fiber Pan Gasket

Farpak is used by most professional transmission shops.  If the pan comes off, a new gasket should go on. It's simply a fiber/neoprene composite gasket, not a true reusable like a silicone w/steel core. If you want it to last longer, you could apply some light grease or TransGel to the surfaces, which should reduce the sticking.

Farpak is miles ahead of a cork gasket for an automatic transmission.