Where is the transmission filter on a 1990 Buick Century?

The 1990 Buick Century, depending on the transmission type (3-speed automatic or 4-speed automatic), doesn't have a readily accessible spin-on transmission filter like some vehicles. Instead, the transmission fluid is filtered *internally* within the transmission itself. There's no external filter to change.

Therefore, there's no transmission filter location to be found. When a transmission service is performed, the fluid is drained and refilled, relying on the internal filter to do its job. Eventually, the internal filter will need to be replaced as part of a more extensive transmission service or rebuild, but that's not a typical DIY maintenance item.