After that, the plug was always wire. All
tapered plugs need to be wired. Worst case is a transmission. The fill and
drain plugs get loose when the trans is hot. Tight again when cold.
The plug gets to
the same temp as the pan,
so thermal expansion shouldn’t change things. Perhaps it wasn’t
tightened properly? I have a brass plug in aluminum pan, and it is tight
when hot or cold.
Al