A process for producing hermetically sealed filters is disclosed. The process includes the steps of providing thermoplastic base and top filter parts and a section of filtration media, sandwiching the media between sections of the base and top filter parts under a compressive force, applying a rapidly repetitive force to at least one of the filter parts to cause movement between the parts and frictional welding of the parts, maintaining the compressive force after frictional welding to allow the melted portion of the parts to solidify and thereby form a fluid seal at the junction of the filter parts and at the junctions of the filtration media and each of the base and top filter parts. In one embodiment, the junction between the filter parts is the periphery of an automatic transmission filter, and the junction is hermetically sealed. A hermetically sealed automatic transmission filter is also disclosed.